Functional Dystonia: Differentiation From Primary Dystonia and Multidisciplinary Treatments

Abstract

Dystonia is a common movement disorder, involving sustained muscle contractions, often resulting in twisting and repetitive movements and abnormal postures. Dystonia may be primary, as the sole feature (isolated) or in combination with other movement disorders (combined dystonia), or as one feature of another neurological process (secondary dystonia). The current hypothesis is that dystonia is a disorder of distributed brain networks, including the basal ganglia, cerebellum, thalamus and the cortex resulting in abnormal neural motor programs. In comparison, functional dystonia (FD) may resemble other forms of dystonia (OD) but has a different pathophysiology, as a subtype of functional movement disorders (FMD). FD is the second most common FMD and amongst the most diagnostically challenging FMD subtypes. Therefore, distinguishing between FD and OD is important, as the management of these disorders is distinct. There are also different pathophysiological underpinnings in FD, with for example evidence of involvement of the right temporoparietal junction in functional movement disorders that is believed to serve as a general comparator of internal predictions/motor intentions with actual motor events resulting in disturbances in self-agency. In this article, we present a comprehensive review across the spectrum of FD, including oromandibular and vocal forms and discuss the history, clinical clues, evidence for adjunctive “laboratory-based” testing, pathophysiological research and prognosis data. We also provide the approach used at the Massachusetts General Hospital Dystonia Center toward the diagnosis, management and treatment of FD. A multidisciplinary approach, including neurology, psychiatry, physical, occupational therapy and speech therapy, and cognitive behavioral psychotherapy approaches are frequently required; pharmacological approaches, including possible targeted use of botulinum toxin injections and inpatient programs are considerations in some patients. Early diagnosis and treatment may help prevent unnecessary investigations and procedures, while facilitating the appropriate management of these highly complex patients, which may help to mitigate frequently poor clinical outcomes.

Full text

REVIEW
published: 04 February 2021
doi: 10.3389/fneur.2020.605262
Frontiers in Neurology | www.frontiersin.org 1February 2021 | Volume 11 | Article 605262
Edited by:
Emmanuel Roze,
Assistance Publique Hopitaux De
Paris, France
Reviewed by:
Abhimanyu Mahajan,
Rush University Medical Center,
United States
Matteo Bologna,
Sapienza University of Rome, Italy
*Correspondence:
Christopher D. Stephen
cstephen@mgh.harvard.edu
Specialty section:
This article was submitted to
Movement Disorders,
a section of the journal
Frontiers in Neurology
Received: 11 September 2020
Accepted: 31 December 2020
Published: 04 February 2021
Citation:
Frucht L, Perez DL, Callahan J,
MacLean J, Song PC, Sharma N and
Stephen CD (2021) Functional
Dystonia: Differentiation From Primary
Dystonia and Multidisciplinary
Treatments. Front. Neurol. 11:605262.
doi: 10.3389/fneur.2020.605262
Functional Dystonia: Differentiation
From Primary Dystonia and
Multidisciplinary Treatments
Lucy Frucht 1, David L. Perez 2,3,4 , Janet Callahan 5, Julie MacLean 6, Phillip C. Song 7,
Nutan Sharma 3,8 and Christopher D. Stephen 3,8
*
1Faculty of Arts and Sciences, Harvard University, Boston, MA, United States, 2Cognitive Behavioral Neurology Unit,
Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States,
3Functional Neurological Disorder Research Program, Department of Neurology, Massachusetts General Hospital and
Harvard Medical School, Boston, MA, United States, 4Neuropsychiatry Division, Department of Psychiatry, Massachusetts
General Hospital and Harvard Medical School, Boston, MA, United States, 5MGH Institute of Healthcare Professionals,
Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States, 6Occupational Therapy
Department, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States, 7Department of
Otolaryngology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, United States, 8Dystonia
Center and Movement Disorders Unit, Department of Neurology, Massachusetts General Hospital and Harvard Medical
School, Boston, MA, United States
Dystonia is a common movement disorder, involving sustained muscle contractions,
often resulting in twisting and repetitive movements and abnormal postures. Dystonia
may be primary, as the sole feature (isolated) or in combination with other movement
disorders (combined dystonia), or as one feature of another neurological process
(secondary dystonia). The current hypothesis is that dystonia is a disorder of distributed
brain networks, including the basal ganglia, cerebellum, thalamus and the cortex resulting
in abnormal neural motor programs. In comparison, functional dystonia (FD) may
resemble other forms of dystonia (OD) but has a different pathophysiology, as a subtype
of functional movement disorders (FMD). FD is the second most common FMD and
amongst the most diagnostically challenging FMD subtypes. Therefore, distinguishing
between FD and OD is important, as the management of these disorders is distinct. There
are also different pathophysiological underpinnings in FD, with for example evidence of
involvement of the right temporoparietal junction in functional movement disorders that
is believed to serve as a general comparator of internal predictions/motor intentions
with actual motor events resulting in disturbances in self-agency. In this article, we
present a comprehensive review across the spectrum of FD, including oromandibular
and vocal forms and discuss the history, clinical clues, evidence for adjunctive
“laboratory-based” testing, pathophysiological research and prognosis data. We also
provide the approach used at the Massachusetts General Hospital Dystonia Center
toward the diagnosis, management and treatment of FD. A multidisciplinary approach,
including neurology, psychiatry, physical, occupational therapy and speech therapy, and
cognitive behavioral psychotherapy approaches are frequently required; pharmacological
approaches, including possible targeted use of botulinum toxin injections and inpatient

Frucht et al. Functional Dystonia: Diagnosis and Treatment
programs are considerations in some patients. Early diagnosis and treatment may help
prevent unnecessary investigations and procedures, while facilitating the appropriate
management of these highly complex patients, which may help to mitigate frequently
poor clinical outcomes.
Keywords: dystonia, functional dystonia, functional movement disorder, functional neurological disorder,
therapeutics
INTRODUCTION
Dystonia is a common movement disorder involving sustained
muscle contractions, often resulting in twisting and repetitive
movements and abnormal postures related to an imbalance
of agonist and antagonist muscles (1). Dystonia may indicate
the presence of many neurological disorders—involving a
primary dystonia, which may be the sole feature (isolated)
or in combination with other movement disorders (combined
dystonia), or as a feature of another neurological process
(secondary dystonia) (1). Furthermore, although many forms
of dystonia do not have any identified genetic underpinnings
(idiopathic dystonia), several genetic forms have been identified,
most commonly DYT-TOR1A (DYT1), DYT-THAP1 (DYT6),
and DYT-GCH1 (dopa-responsive dystonia) (2). Dystonia is
common, with an estimated prevalence of up to 1 in 1,000
individuals, which is notable, given diagnostic challenges
frequently leading to misdiagnosis or under-diagnosis (3,4). The
anatomical basis and pathophysiology of dystonia is unknown,
with neuropathology generally not revealing brain degeneration
except in the case of X-linked dystonia parkinsonism (DYT-
TAF1 [DYT3]) (2). The current hypothesis is that dystonia
is a disorder of brain networks, including the basal ganglia,
cerebellum, thalamus and cortex, resulting in abnormal neural
motor programs (5). Table 1 illustrates the range of clinical
presentations in common genetic primary dystonia, including
the phenotype, mode of inheritance and typical age of onset.
Functional dystonia (FD) may resemble other forms of
dystonia (OD) but has a different pathophysiology (10,11), as
a subtype of functional movement disorders (FMD) under the
more general classification of functional neurological disorders
(FND) (12). The study of FND is rapidly developing, as these
are common but still incompletely understood disorders at the
interface between neurology and psychiatry (13). FD is both
phenotypically and phenomenologically diverse, with frequent
mixed presentations with other FMDs and/or other functional
symptoms and can present from childhood to late adulthood
(14). Thus, although FD is the second most common FMD,
it is among the most diagnostically challenging FMD subtypes
(11). Distinguishing between FD and OD is important, as the
management of these disorders is different and appropriate
treatment may lead to symptom resolution in FD (14,15). We
present a comprehensive (long-form) review of the historical
context, clinical clues and features differentiating FD from
OD across the spectrum of FD subtypes (including pediatric
FD), evidence for adjunctive “laboratory-based” testing, and
pathophysiology. In doing so, we outline the approach used at the
Massachusetts General Hospital (MGH) Dystonia Center toward
the diagnosis, management and treatment of this complex set
of disorders.
HISTORICAL CONTEXT
Even after over a century of examination and consideration of
its presentation, symptoms, and diagnostic criteria, FD remains
a challenging movement disorder for neurologists to diagnose,
and patients to understand (16). For this reason, the legitimacy
of FD has historically been heavily debated. For the better part of
the twentieth century, FD was considered purely a manifestation
of “conversion disorder/hysteria,” with physical symptoms and
signs believed by physicians to be entirely psychiatric in nature
(17). However, over time, given growing evidence of genetic
inheritance and its pathophysiological underpinnings, dystonia
was framed as an “organic” neurological disorder (18). Given
this realization, the pendulum then swung in the opposite
direction, whereby FD was felt to be rarely present (19). Time
has eventually confirmed the presence of FD, taking its place
alongside traditional dystonia but inherent difficulties remain,
including that there can be an overlap in these distinct disorders,
adding to the diagnostic and clinical challenges (20). Hence to
understand FD in the present, we first must look to the past.
One of the founders of neurology, Jean-Martin Charcot’s
description of “hysteria” mirrored the typical presentation of
dystonia that doctors faced in the clinic decades later (21). Early
case reports of what is now known to be early-onset generalized
torsion dystonia involved diagnostic impressions punctuated
by a history of psychiatric issues and “hysterical” symptoms
(21). However, in 1911, Hermann Oppenheim provided the first
documentation of dystonia and coined the term. After seeing
several similar unusual cases, he published his observations and
theories about their commonalities, assigning them the label,
“dystonia musculorum deformans” (22). He struggled over the
disorder’s pathogenesis, and ultimately concluded, “I therefore
believe that the affliction we are dealing with today is not a
neurosis but rather originates from subtle changes in the central
nervous system, in special areas that control or influence the
muscle tone and that it will be possible sooner or later to
discover the pathological-anatomical cause” (22). He believed
this first description of generalized dystonia to be a neurological
condition, which appeared familial in some cases but could not
distinguish a pathological cause (22). There was similar dispute
in forms of focal dystonia. In cervical dystonia (torticollis), the
turning of the head was debated to be a peripheral nerve disorder,
while the common presence of a “geste antagoniste,” or sensory
trick (a now typical and widely acknowledged finding suggestive
Frontiers in Neurology | www.frontiersin.org 2February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
TABLE 1 | Common genetic dystonia subtypes [adapted from Klein et al. (6) and Balint et al. (2)].
Classification Designation/Gene
locus
Onset Pattern of
inheritance
Dystonia distribution Other relevant features
Isolated dystonia DYT-TOR1A (DYT1) C AD Generalized • Most common genetic dystonia
• More common in Ashkenazi Jewish ancestry
• Focal onset, frequently in the lower limbs and generalizes
• Reduced penetrance
•DBS highly effective (7,8)
DYT-THAP1 (DYT6) A/C AD (rarely
AR)
Neck, limbs, orofacial,
and larynx
• Often prominent cranial involvement
•DBS beneficial (7,8)
DYT-ANO3 (DYT24) A/C AD Neck, larynx, orofacial,
and upper limbs
• Onset typically cervical
DYT-GNAL (DYT25) A AD (rarely
AR)
Neck limbs, orofacial,
and larynx
Combined
dystonia
Parkinsonism DYT/PARK-TAF1
(DYT3)
A XR Orofacial, neck, limbs,
and trunk
• Filipino ancestry, often to Panay Island
• Wide phenotypic spectrum ranging from severe generalized
dystonia, pure parkinsonism or combination
• Unique dystonic parkinsonian gait (9)
• MRI with striatal atrophy
•DBS beneficial (7,8)
DYT-GCHI (DYT5a) C AD (rarely
AR)
Limbs and trunk • Dopa-responsive
• Diurnal variation (worse in evenings)
• Spasticity
• Familial “cerebral palsy”
DYT-TH (DYT5b) C AR Limbs, trunk, and
orofacial
•Dopa-responsive
• Diurnal variation
• Gait disorder
• Myoclonus
• Spasticity
• May be associated with oculogyric crises
•DBS beneficial (7,8)
DYT-SPR C AR (rarely
AD)
•Dopa-responsive
• Diurnal variation
• Intellectual/developmental delay
• High CSF biopterin/dihydrobiopterin
• May be associated with oculogyric crises
DYT-ATP1A3 (DYT12) A/C AD Orofacial, cervical, larynx,
and limbs
• Clinical heterogeneity:
- Alternating hemiplegia of childhood
- Rapid onset dystonia parkinsonism
·Common bulbar involvement
- Cerebellar ataxia, areflexia, pes cavus, optic atrophy
(CAPOS)
• Sudden onset after infection/febrile illness
• Fluctuating course
• Exacerbations with fever, physical stress, alcohol
• Chorea
• May have seizures
DYT-PRKRA (DYT16) C AD Orofacial, larynx, neck,
trunk, and limbs
• Hyperreflexia
Myoclonus DYT-SGCE (DYT11) C AD Neck, upper limbs, and
orofacial
• Alcohol dependence (improves myoclonus)
• Neuropsychiatric symptoms
•DBS beneficial (7,8)
DYT- KCTD17 (DYT26) A/C AD Cranial and cervical
DYT- KMT2B (DYT28) C AD Orofacial, larynx, neck,
limbs, and trunk (may
have myoclonus)
• Microcephaly
• Short stature
• Neuropsychiatric symptoms
• Intellectual/developmental delay
• Oculomotor apraxia
• “Cerebral palsy”
•DBS beneficial (7,8)
(Continued)
Frontiers in Neurology | www.frontiersin.org 3February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
TABLE 1 | Continued
Classification Designation/Gene
locus
Onset Pattern of
inheritance
Dystonia distribution Other relevant features
Paroxysmal PxMD-PRRT2
(DYT10/19)
C AD • Paroxysmal kinesogenic dyskinesia (PKD)
• Attacks triggered by sudden voluntary movements, stress,
startle, sleep deprivation
• Migraine (may be hemiplegic)
• May have epilepsy
PxMD-PNKD
(DYT8/20)
C AD • Paroxysmal non-kinesogenic dyskinesia (PNKD) with
choreoathetosis, ballismus
• Attacks triggered by alcohol, caffeine stress, hunger,
fatigue, tobacco
PxMD-SLC2A1
(DYT9/18)
C AD Legs most commonly • Paroxysmal exertional dyskinesia (PED) with
choreoathetosis
PxMD-ECHS1 C AR • Paroxysmal exertional dyskinesia (PED)
• Severe developmental delay
• Infantile encephalopathy with choreoathetosis
• Optic atrophy
• Cardiomyopathy
• Sensorineural hearing loss
ADFLE (CHRNA4) C AD • Paroxysmal hypnogenic dyskinesias
Other DYT-TUBB4A (DYT4) A/C AD Orofacial, larynx, neck,
and limbs
• “Whispering” dysphonia
• “Hobby horse” gait
• Ptosis, edentulous, facial atrophy
DYT- MECR (DYT29) C AR Generalized • Optic Atrophy
• Basal ganglia abnormalities
CHOR/DYT-ADCY5 C AD, de novo,
rare AD
Generalized • Axial hypotonia
• Developmental delay
• Facial twitching
• Chorea
• Myoclonus
• Oculomotor apraxia
• Triggered by sleep transitions, emotional stress, illness,
sneezing, caffeine
ACTB C AD Generalized • Sensorineural deafness
• Intellectual/developmental delay
• Dysmorphic facies
•DBS beneficial (7,8)
AD, autosomal dominant; AR, autosomal recessive; XR, X-linked recessive; A, adult onset; C, childhood onset; CSF, cerebrospinal fluid; DBS, deep brain stimulation; ADFLE, autosomal
dominant frontal lobe epilepsy. Bolding in table is used for emphasis of particularly important features.
of dystonia), was given as evidence by Charcot of its psychological
origins (21). Writer’s cramp, a focal hand dystonia, received a
similar fate, where the eminent neurologist, Guillaume Duchenne
described this as “spasme fonctionnel” (23), a neurological
disorder but others focused on the etiological role of personality
traits (21,23). Contemporaneous with Oppenheim, neurologist
Sigmund Freud was gaining traction for his theories and practices
of psychoanalysis to treat “conversion disorder” (24). The
symptoms of hysteria resembled neuroses but had unknown
pathology and were felt to be usually triggered by an emotional
or traumatic event, with physical manifestations resulting from
internal psychological conflict (25). Therefore, dystonia came to
be regarded as a form of “conversion disorder”; a psychological
phenomenon, which was treated with psychotherapy (21).
Through the mid-twentieth century, dystonia presentations
such as blepharospasm were treated primarily with long-term
psychotherapy and other, sometimes experimental psychiatric
treatments (26). Although met with limited success, attempts
at more medicalized treatments, such as eye drops and carbon
dioxide treatments, proved futile (27). In one case, a man with
blepharospasm who claimed no psychiatric history improved
immediately with the administration of a central nervous
system stimulant, suggesting a relationship between his dystonia
and underlying depression (27). In addition, cervical dystonia
was treated with psychotherapy, anxiolytics, behavioral therapy
or aversive therapies (28). However, these conventions were
challenged by a growing body of evidence culminating with
studies in the 1960s identifying the neuropathologic basis
of dystonia (29). Firstly, psychotherapy did not produce the
expected benefits seen in other traditional forms of “hysteria”
(30). In addition, surgery to the thalamus or globus pallidus
[typical targets for current deep brain stimulation (DBS) in OD]
yielded substantial clinical benefit, and the first animal model of
dystonia, following lesioning of the basal ganglia, was produced
in 1965 by Denny-Brown, one of the pioneers of American
neurology (10,31,32).
By the 1970s, David Marsden popularized dystonia’s
neurological features and sidelined FD as a markedly uncommon
Frontiers in Neurology | www.frontiersin.org 4February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
entity (21). He described several features leading to dystonia
being erroneously considered as “psychogenic,” including the at
times bizarre phenomenology of the movements, the inexplicable
task-specificity, the presence of sensory tricks, typical worsening
with stress and anxiety, and lack of abnormalities on diagnostic
testing (33). As such, many doctors viewed a FD diagnosis
as exceedingly rare, or perhaps did not even exist (19). A
study from 1978 examined the differences in patients with
idiopathic dystonia, having the potential to be characterized as
“psychogenic,” and those whose dystonia had a known cause or
family history and ultimately determined that only 1 out of 85
cases were “psychogenic” in origin (34). With the understanding
of the frequency of psychiatric symptoms in dystonia, this led
to a shift in favor of a neurological definition of dystonia (35).
Subsequently, in the 1970s and 1980s, there were a deluge of
cases detailing misdiagnosis of dystonia as “psychogenic” and
highlighting the medical and legal perils of this formulation
(34,36,37).
Later, neurological cases of “psychogenic” dystonia
responding to psychotherapeutic treatment were reported
in the late 1970’s and early 1980’s (21). This again came from
leaders in the field, and while Stanley Fahn reported the first cases
of FD, he still considered this a rare entity (34,38). Following
further evidence from an expanding number of cases, Fahn and
Williams set out the first diagnostic definition of FD (39).
Despite the clarification brought by initial and subsequently
updated diagnostic criteria (40), diagnosis of FD remains
challenging to general neurologists and movement disorders
specialist alike, with poor interrater reliability (41,42).
Additionally, the shift from “psychogenic” to “functional”
dystonia occurring in the twenty-first century (43) seeks to
provide an etiologically neutral framing of this condition—one
that acknowledges that this neuropsychiatric condition sits
at the intersection of neurology and psychiatry (44). Current
research efforts therefore aim to identify features which reliably
differentiate FD from OD, with the addition of potential
adjunctive testing techniques to further define these two
disorders (11).
RISK FACTORS FOR FUNCTIONAL
DYSTONIA
FD has several predisposing vulnerabilities, some of which are
similar to those of primary OD. FD is more common in females
than males (as is typical for FND in general) and has a typical
age of onset of 29–50 years, depending on the population tested,
compared to a generally childhood, adolescent or early adult-
onset in most genetic dystonias (45). Although FD is generally
less common in children and the elderly, there is increasing
recognition of FD and FMD in general in these populations
(45–47). FD is also seemingly more common among white
individuals, although this association may be in part related to
lack of diversity in research cohorts published to date (45). Of
note, this is also frequently the case for OD, where particularly
in genetic forms (particularly DYT-TOR1A/DYT1), individuals
of Ashkenazi Jewish origin are at higher risk (34,45). Based on
the biopsychosocial formulation, predisposing, precipitating and
perpetuating factors are shown in Table 2 (48).
Family history also plays a role in risk for FD, and FMD
more broadly, as well as OD. Despite this, although patients
with FD commonly have no family history of dystonia or other
movement disorders (34), there is influence of a family history
of neurologic and psychiatric disorders on an individual’s risk for
developing FD (49). A family history of movement disorders has
also been shown to increase risk, through potentially patterning
motor behaviors, and there have been reports of familial FMD
(49). OD may be idiopathic and several genetic forms have been
described, with considerable clinical heterogeneity in patients
with a certain gene [see Table 1; (50)]. Patients with DYT1,
the most common genetic dystonia, may also not necessarily
have a family history, as there is reduced penetrance in roughly
30%, with frequent non-manifesting carriers (49,51). Different
genetic movement disorders phenotypes are also differentially
impacted by genotype. For instance, primary paroxysmal
dyskinesias associated with the PRRT2,GLUT-1, and MR-1
genes are associated with distinct presentations (paroxysmal
kinesogenic dystonia, paroxysmal non-kinesogenic dystonia
and paroxysmal exercise-induced dyskinesia, respectively) and
respond to particular treatments (52). However, over time, these
diagnostic silos are becoming less robust, with increasing clinical
and genetic heterogeneity (53,54).
Psychiatric symptoms are also frequently associated with FD,
with anxiety and depression being the most common psychiatric
comorbidities (46). Furthermore, in a study comparing FD and
OD patients, a major depressive episode occurring prior to
dystonia onset was a significant predictor of a FD diagnosis (55).
However, it is notable that anxiety, depression and suicidality
are also more common in OD than in the general population
(56). Personality disorders have also been reported to be more
common in FD vs. OD (55,57). There is evidence to support
that patients with FD also tend to have a more stressful social
environment than OD and typically display less extroversion or
openness (55).
DIAGNOSIS OF FUNCTIONAL DYSTONIA
Diagnostic criteria for FD and other FMD has undergone
several iterations in recent decades (58). The first official criteria
established by Fahn and Williams in 1988 were only for FD
(39), and included four diagnostic categories: documented,
clinically-established, probable, and possible FD [Table 3; (16,
58)]. In the documented and clinically-established category,
incongruence or inconsistency of movements with classical OD
were required to make a diagnosis (39,40). Other clinically
supportive criteria included the presence of other functional
neurological signs, other somatic symptoms (somatization),
or “obvious psychiatric disturbance” (39). In a revision in
1995, the documented and clinically-established categories were
collapsed to both constitute “clinically definite” FMD (59).
Without further evidence of a functional cause, the presence
of only incongruence or inconsistency constituted a clinically
probable case. The clinically-possible category included only
Frontiers in Neurology | www.frontiersin.org 5February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
TABLE 2 | The biopsychosocial model: predisposing, precipitating, and perpetuating factors for the development and maintenance of functional dystonia and related
functional neurological disorders [adapted from McKee et al. (48)].
Biological Psychological Psychosocial
Predisposing
vulnerabilities
• Sex—female
• Intellectual disability
• Comorbid neurological conditions
• Other nervous system vulnerabilities
• Co-morbid functional somatic disorders (i.e.,
fibromyalgia, irritable bowel syndrome, other
chronic pain disorders)
• Sensory processing difficulties sensory
processing difficulties
• Comorbid mood and anxiety disorders,
PTSD, personality disorders
• Dissociation
• Alexithymia
• Insecure attachment
• Temperament and maladaptive personality
traits (i.e.,
obsessive-compulsive, neuroticism)
• Family functioning/childhood neglect
• Chronic illness in family
• Traumatic death in family
• Adverse life experiences (divorce in childhood,
home life or personal relationships)
• Physical, sexual, or emotional abuse
• Financial difficulties
• Inadequate social supports
• Attitudes toward health and disease
• Symptom modeling for dystonia/abnormal
movement (through family history, as patterning)
Precipitating
factors
• Abnormal physiological event(s), such as sleep
deprivation, sleep paralysis, hypnic jerks,
hyperventilation, palpitations
• Physical precipitating event (acute pain;
peripheral limb injury or head trauma; dizziness
caused by vestibular event; surgical
intervention)
• Initial motor compensation following an injury
(such as to avoid pain)
• Emotional reactions to physical injury or
other life events (sudden loss of loved one,
sudden change in social or financial
situation, relationship breakdown etc.)
• PTSD trigger or flashback
• Perception of event as traumatic/negative
• Dissociative event
• Panic attack (including dizziness as part
of panic)
• Loss of employment or other occupational
difficulty
• Divorce or marital strain
• Traumatic death of loved one
• Other relational stress
Perpetuating
factors
• Physiological arousal
• Chronic pain
• Chronic fatigue
• Abnormal motor habit formation
• Deconditioning
• Other medical/neurological comorbidities
limiting treatment participation
• Fixed posturing leading to contractures
• Risk if motor pattern is continuous (particularly
in fixed posture), this may lead to irreversible
changes in the motor program and lack
of reversibility
• Negative expectation bias
• Negative attentional bias
• Illness beliefs including perception of
symptom irreversibility or attribution to
another cause (of the patient or significant
others)
• Fear of falling
• “No pain no gain” philosophy to healing
• Avoidance of symptom exacerbation
• Hypervigilance and dissociation
• Lack of acceptance of functional
neurological disorder formulation
• Not feeling believed
• Maladaptive behaviors (reliance on walking
aids/wheelchair etc.)
• Identity linked to rigid concepts around
productivity, self-efficacy
• Provider diagnostic uncertainty (ambiguous
diagnosis and ongoing investigations)
• Social benefits of being ill (often out of
awareness)
• Reliance on care and disability benefits
• Pending litigation and compensation claims
• Workmen’s compensation/disability
• Poor care coordination
• Poor family buy in/support of diagnosis and
treatment plan
• Employer or patient urgency to return to work
• Ongoing social difficulties (relationship, financial,
loss of roles etc.)
• Social stigma around functional neurological
disorder
• Role in other disorder support groups
Note, the above list is not exhaustive but rather is representative of the commonly encountered factors that are relevant to consider in developing a patient-oriented biopsychosocial
formulation. Also, a given factor may relate to multiple categories, such as alexithymia could be both a predisposing vulnerability and a perpetuating factor. PTSD, post-traumatic
stress disorder.
obvious emotional disturbance, the symptom that is now
considered least reliable in diagnosing FD out of the original
criteria (40).
In 2006, Shill and Gerber proposed a new set of
criteria for FMD diagnosis, removing the necessity for
incongruence/inconsistency, replacing a “necessary and
sufficient” classification with a combination of primary
symptoms (40). These symptoms, categorized under
clinically-definite, included pain, fatigue, exposure to a
disease model, and potential for secondary gain, while
multiple somatizations and psychiatric disturbance were
considered secondary to those criteria (40). Probable and
possible categories had fewer of the diagnostically reliable
symptoms (58). These criteria have been criticized for their
removal of inconsistency and incongruence from the diagnostic
criteria, which many neurologists believe are the most critical
factors in making an accurate diagnosis, particularly in
FD (40).
Gupta and Lang’s 2009 FMD criteria removed clinically-
probable and possible from the potential diagnosis, leaving
just clinically-definite criteria from Fahn and Williams’ initial
outline (58). Their modifications also included increased
emphasis on laboratory-supported diagnosis (particularly with
neurophysiology), and generally minimized the importance of
emotional disturbance and patient history in the diagnosis (60,
61). The authors believed false positive diagnoses were sometimes
related to a patient presenting with a neurological disorder
accompanied by additional psychiatric symptoms, but that this
did not constitute a FMD (40).
Although the diagnosis of FD can have helpful associated
historical features, diagnosis is made primarily from “rule-in”
neurological examination features similar to other FMD, which
Frontiers in Neurology | www.frontiersin.org 6February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
TABLE 3 | Functional dystonia diagnostic criteria [Fahn and Williams (39)].
Documented#Persistent relief by: psychotherapy; psychological suggestion including physical therapy, or by administration of placebo; or if witnessed
symptom-free when left alone believing to be unobserved*
Clinically established#Dystonia is inconsistent over time or incongruent with classical dystonia (cannot move limbs on request or resistance with passive movement and
contrast with ability to perform daily tasks) and at least one of the following:
1. Other “psychogenic” (functional) neurological signs (give-way weakness, “false” sensory findings etc.)
2. Multiple somatizations
3. Obvious psychiatric disturbance
Probable 1. Dystonic movements inconsistent or incongruent with classical dystonia but no other “psychogenic” (functional) features
2. Dystonic movements are consistent and congruent with organic dystonia but there are additional definite “psychogenic” (functional) neurological
signs
3. Dystonic movements are consistent and congruent with organic dystonia but there are multiple somatizations
Possible Dystonic movements are consistent and congruent for organic dystonia but with obvious emotional disturbance
*The authors do mention a caveat, that in making a documented “psychogenic” (functional) dystonia diagnosis that there must not simply be improvement under hypnosis or when using
sedatives, as they describe that other forms of dystonia can also improve with these. They also describe rare spontaneous remissions in “organic” dystonia (with an example being cervical
dystonia) and that otherwise improvement in “organic” dystonia is typically incomplete and temporary, whereas functional dystonia was noted to have traumatic, sudden improvement.
#In a 1995 revision, Documented and Clinically established diagnoses were collapsed into a new category “Clinically Definite” (59). Bolding in table is used for emphasis.
are inconsistent with OD (40,62). In an international study
of neurologists on their FMD diagnostic practices, two thirds
of participants reported having access to electrophysiological
laboratory testing to help or confirm their diagnosis (63). In some
cases, ordering electrophysiological or other neurological tests
may be used as a signal to the patient that the physician is taking
their condition seriously, although most often tests are only
used in unusual cases when the diagnosis is otherwise unclear
(63). Most neurologists reported often referring patients to a
psychiatrist for further diagnostic consultation, even if a FMD
diagnosis had already been made by the neurologist (63). This
may lead to potential issues with the psychiatrist challenging the
diagnosis, including reports of no clear “psychiatric diagnosis”
being found (64).
There are several challenges in diagnosing FMD, and
particularly FD. First, OD may be mistaken for other conditions
such as tremor or Parkinson’s disease (65). In addition, particular
ODs commonly misdiagnosed as FD include paroxysmal
dystonia/dyskinesia (52,53), task-specific dystonias (66,67),
dopa-responsive dystonia and other potentially treatable
metabolic movement disorders (68), rapid-onset dystonia-
parkinsonism (69), and acute drug-induced and tardive dystonias
(57). There are also the various non-FND pseudodystonias
(e.g., abnormal postures related to atlanto-axial subluxation,
compensatory movements after injury, or similarities in
presentation in pathological muscle stiffness/myotonia, etc.),
which mimic the appearance of dystonia but result from
musculoskeletal disease or dysfunction in the sensory, motor or
other neurological pathways (70).
In addition, diagnoses can further be confounded by
the presence of FD and other functional neurological
symptoms presenting in patients with other neurological
disorders, such as the presence of FMD in Parkinson’s disease
(occurring in 1.4–7.5% in Parkinson’s disease patients) (71)
or functional seizures in the setting of epilepsy (one in five
patients with functional seizures also has epileptic seizures)
(72). These two concurrent processes require different
treatments and their co-occurrence can at times be challenging
to manage.
Incorrect diagnoses may lead to unnecessary investigations,
increased healthcare costs (73), iatrogenic harm, possible
inclusion in inappropriate clinical studies, and poor prognosis
(74,75). Yet, as has been described, the identification of
features incongruous and inconsistent with OD are complicated
and based on familiarity with complex and atypical dystonia
cases, while also relying on clinicians being comfortable with
eliciting diagnostic functional neurological examination signs.
It is therefore generally recommended that only a specialist
with expertise in distinguishing dystonia from other movement
disorders, and FD from other neurological disorders, make
the diagnosis of FD (40). However, despite this, diagnostic
uncertainty even among movement disorders experts is high,
particularly for the most challenging cases (41,42).
DISTINGUISHING CLINICAL FEATURES OF
FUNCTIONAL DYSTONIA
OD and FD are not mutually exclusive; patients may present with
both functional neurological symptoms and other movement
disorders, including OD (21,71,76). It is therefore important to
closely follow patients over time, particularly in more ambiguous
cases with less diagnostic certainty for a definite FD, as features
may emerge suggesting an additional or alternative diagnosis
misconstrued to be a FMD (77). Hence, it is vitally important to
use accepted diagnostic signs in the context of pertinent historical
features in a skilled provider to properly distinguish FD from OD.
Historical Clues Favoring a Functional
Dystonia Diagnosis
While not diagnostic, a thorough history frequently reveals
features distinguishing FD from OD. Rather than a gradual
progression of symptoms, as is generally seen in OD, FD patients
commonly report a sudden onset of maximal symptom severity
and rapid symptomatic progression (78). Furthermore, in FD,
symptoms often arise in response to a physical precipitating
event or injury but also stressful or traumatic experiences, or a
reminder of such events (79). Peripheral trauma can result in a
Frontiers in Neurology | www.frontiersin.org 7February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
range of neurological disorders, including FMDs, particularly in
the setting of innocuous trauma (80,81). Spontaneous remissions
and subsequent recurrences may also occur in FD and while such
remission is very rare in OD, this can be seen, predominantly in
cervical dystonia and blepharospasm (82).
Childhood maltreatment (including neglect) represent
another risk factor for FD. Such sensitive information may
only be revealed if there is sufficient rapport with the clinician.
However, when speaking sensitively and empathetically, such
information may be succinctly explored even on the first visit if
sufficient time allows (83). Compared to OD, patients with FD
are also more likely to have psychiatric disorders, particularly
anxiety and depression (84); distinct personality traits (85) and
psychological profiles, including dissociation, alexithymia, and
insecure attachment, are also more common in FND (86). FD
also tend to have higher levels of somatic symptom disorder and
other functional somatic disorders [e.g., fibromyalgia, irritable
bowel syndrome etc.; (58,78,87)].
Pain and Functional Dystonia
FD patients commonly experience pain in both affected
regions/limbs and in other body areas (15,88), and the presence
of pain is associated with worse outcomes (15,88,89). In
comparison, pain is less common in OD, other than in cervical
dystonia, where it can contribute to significant disability (90,91).
In Schrag et al.’s large series of fixed dystonia, 20% fulfilled
criteria for Complex Regional Pain Syndrome (CRPS) (92).
The association between CRPS and different forms of dystonia
was first described in 1986 (93,94). CRPS involves localized
pain, including the presence of allodynia, hyperpathia, swelling,
sudomotor, and vasomotor changes, as well as autonomic
changes involving both skin color and temperature (80,92).
CRPS is differentiated into two types: type 1 (CRPS-1) occurs in
the absence of a nerve lesion, and is the subcategory associated
with FD, while in type 2, there is a distinct peripheral or
more proximal nerve injury (92). Several diagnostic criteria
and characteristic attributes of CRPS-1 are similar to that of
FMD (92). For example, CRPS-1 may be similarly inconsistent
with other pain disorders and symptoms may be distractible
(92). Pain may travel between limbs or affected regions, in the
absence of a further injury or inciting event. CRPS also tends
to occur suddenly, similar to the abrupt onset typical of FD
but not OD (80). Not surprisingly, debate over the neurologic
and psychiatric roots of CRPS has mirrored that of FD (92).
The origins and pathogenesis of CRPS-1 and dystonia, the
“causalgia-dystonia” syndrome, are unknown (80). Hypotheses
include that abnormal contractions and posturing of FD are
conditioned responses to pain, with heightened expectation of
pain triggering disordered movements (92). Other hypotheses
focus on the origins of motor control and pain within the
central nervous system. For example, neuroimaging studies
have examined the overlap between pain and motor control
regions as potentially significant in facilitating these associations
(92). Another hypothesis contends that abnormal sensorimotor
integration contributes to peripheral pain and posturing (95).
The undetermined pathogenesis of CRPS-1 has led to frequently
inadequate treatment, concentrated on pain alleviation rather
than a more comprehensive approach (16,80). The increasing
recognition of sensory processing difficulties in motor FND may
also be relevant in FD, an area in need of further investigation
(96). In extreme cases, the patient may even seek amputation as a
means to alleviate their suffering (16,97). Such a drastic approach
has also been reported in fixed FD as a last resort, following
inadequate treatment (98). The reason for this tendency to opt
for amputation, similar to that seen in CRPS has been postulated
to be related to deficits in body schema and may represent a form
of body integrity identity disorder (98).
Clinical Examination Presentation of
Functional Dystonia
The range of published and anecdotal clinical features
of FD found by our group are shown in Figure 1 and
Supplementary Table 1. A core feature of OD is the internally
consistent and stereotyped nature to the movements themselves
(although there may clearly be variation depending on certain
tasks). In comparison, as a fundamental feature, the nature
of FD movements is both incongruous with that seen in OD
(such as early fixed posturing, or dystonia initially occurring at
rest) but also the movements themselves are highly internally
inconsistent and variable, sometimes involving multiple different
semiologies of abnormal postures (11). FD symptoms may also
greatly fluctuate, such as between taking history and conducting
the physical examination (a patient’s gait entering the clinic
may differ from their atypical gait during examination or
marked worsening provoked by video recording) (29,34,78).
Similarly, symptoms may also appear more frequently during
the clinical assessment than the patient reports as typical in their
everyday life, owing to this heightened sense of attention, as
well as the increased anxiety state associated with the clinical
encounter (83). These features are consistent with the role of
attention in amplifying functional neurological symptoms more
broadly (108).
Other general principles of FD can include: (i) lack of a
rostrocaudal gradient seen in OD; (ii) rapid spread from a
focal to multifocal or generalized distribution; (iii) widespread
distribution at onset; (iv) and spread beyond presenting
symptoms given that dystonia generally remains focal in adult-
onset idiopathic dystonia (39). There may also be inconsistency
in distribution over time, with a pattern of distribution
sometimes appearing random or cyclical, in contrast to static
symptoms or a methodical spread seen in OD (78). If the
posturing in FD is not fixed, it may be distractible and
suppressed by tasks such as finger-tapping/mental arithmetic, or
by suggestion (such as the use of a tuning fork), in comparison
to OD (109,110). As a caution, although bizarre movements
and postures are frequent in FD, it is important to acknowledge
that unusual posturing, particularly in younger patients, can be a
harbinger of rare genetic (2), autoimmune [e.g., NMDA-receptor
antibody encephalitis], (111), toxic (112), or metabolic OD (113).
This is important to note, as secondary dystonia can potentially
be treatable depending on the underlying cause, particularly in
metabolic disorders (114). The presence of other FMDs is a
hallmark of FD (58). Another important feature which can be
Frontiers in Neurology | www.frontiersin.org 8February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
FIGURE 1 | Clinical clues for functional dystonia subtypes. This schematic represents an abbreviated list of potential clinical clues. For the full list, please see
Supplementary Table 1. CRPS-1, complex regional pain syndrome type 1. *Previously published (16,39,52,99–107).
Frontiers in Neurology | www.frontiersin.org 9February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
present in OD but not FD is the presence of sensory tricks, which
are frequently atypical or absent in FD but in comparison, are
reasonably common in OD, found in more than half of patients
with facial/cervical dystonia (16,115). Examples of FD clinical
phenomenology are shown in Figure 2.
Clinical Features of Common Functional
Dystonia Phenotypes
Limb
Abnormal limb posture, particularly involving the hands and
feet are common in FD. Patients may experience posturing and
contractions of multiple limbs simultaneously, and symptoms
may travel across limbs (116). Examples of common functional
dystonic lower limb postures include foot plantarflexion and
inversion, and first toe extension as other toes flex (58,99), as
illustrated in Figure 2C. In the upper extremities, FD frequently
manifests as wrist and finger flexion, sometimes with a clenched
fist and generally involving the dominant side (78,117). If
there is more proximal involvement, combined wrist and
elbow flexion are typical (58,99), as shown in Figure 2D. FD
posturing is more often fixed than in OD, where symptoms
are usually mobile, dynamic and may be task-specific (83). In
particular, fixed dystonia at onset is a common FD presentation
but highly atypical for OD, where symptoms may become
gradually more fixed over time, related to progressively more
severe and persistent posturing, although there is still generally
an additional spasmodic, dynamic element (12). In FD, limb
dystonia frequently starts in the foot, however adult leg dystonia
is rare in OD, and uncommon in patients over 30, typically
affecting children (12,88,100). However, focal foot dystonia may
occur as a secondary dystonia, such as in Parkinson’s disease,
particularly in young onset cases (118). In FD, fixed posturing
of the lower limbs causes the patient to drag the affected leg
(sometimes behind the patient, as a dragging monoplegic gait),
which is persistent throughout the gait cycle. Fixed lower limb
FD can be debilitating, may result in loss of ambulation and
is frequently accompanied by pain on attempted movement of
the affected limb, and in some cases, by CRPS-1 (58,99,119).
Other common causes of fixed OD include the dystonia seen
in corticobasal syndrome, which typically starts on the left
(generally non-dominant) side (120). Another peculiarity is that
there is no improvement of limb posturing with sleep in FD,
whereas in OD, symptoms often briefly improve with sleep (88).
Limb FD also may respond to placebo, either with medications
or botulinum toxin injections (121). In addition, the use of
general or local anesthesia may reduce symptom severity or relax
fixed posturing, as well as aiding in the determination of the
presence of contractures (122). If fixed posturing is not reverted,
contractures may develop, which may mimic OD (122).
In FD, when patients attempt voluntary movement to
command in a direction opposite that of the dystonic posturing,
this may activate antagonist muscles but with limited (and in
some cases apparently no) activity in the agonist muscles, which
is very unusual, as co-contraction of antagonistic muscles is a
hallmark of OD (61). There can also be an associated functional
“striatal toe sign” in FD, where in the setting of fixed great
toe extension, there is pain and variable resistance to passive
flexion, whereas forced passive dorsiflexion of the second to fifth
toes causes spontaneous plantarflexion of the great toe. This
is in sharp contrast to an “organic” striatal toe, where there is
no pain or resistance on passive flexion of the great toe and
dorsiflexion of the other toes does not change the great toe
posture (101). Other discriminating examination features include
abilities inconsistent with the degree of abnormal posturing,
active resistance with passive movement (sometimes despite
the appearance of complete immobility), persistent abnormal
posturing when walking backwards (which typically improves
lower limb OD), or the presence of functional weakness or
sensory symptoms (100). Movement of the affected limb may also
be inappropriately slow and ponderous but without triggering
worse posturing, as frequently seen in OD. Straightening out the
FD posture may in rare cases result in a new resting dystonic
posture, or shifting from one posture to another, as per the
“whack-a-mole” sign (102). None of these features are found
in OD.
Cranial—Facial Spasm and Blepharospasm
Encompassing a variety of phenotypes, functional cranial
dystonia encompasses 16% of all FMD (16). Symptoms may
be paroxysmal or persistent, with occasional fixed posturing
and may affect several facial regions (16,103). Like other FD,
the initial onset of functional cranial dystonia and pattern of
subsequent symptoms are abrupt and seemingly random (103).
In functional facial spasms, this tends to involve the lower
face (sometimes at onset) (103,104), with the most common
phenotype (in 84% of patients) being asymmetric tonic jaw/lip
deviation (58,104). An excellent reference is the paper by
Fasano et al., who comprehensively reviewed findings comparing
functional facial spasm to other forms of facial spasm (103). In
comparison to sensory tricks being relatively common in OD,
they appeared rare in FD. Speech is typically normal in OD
with facial spasms/Meige syndrome (unless there is additional
segmental involvement of the vocal cords or oromandibular
dystonia), whereas slurred or hesitant speech is not infrequent
in FD. Activation of accessory neck muscles with platysma
involvement is rare in OD and when it does occur, is bilateral
but is common and ipsilateral in FD. The spasms may be induced
by action in OD, whereas they are frequently paroxysmal in FD,
with episodes of normal facial movement in between. The spread
and progression of OD involving the face is generally segmental,
with spread to the neck, whereas FD is typified by an unusual
and rapid spread to multifocal or more widespread dystonia
distribution (103).
The facial pulling may be synchronous or asynchronous and
there may be tonic deviation, which is not seen in OD (103,
104). An example of bilateral lower facial pulling is shown in
Figure 2A. While the lower face is most commonly affected,
other functional cranial phenotypes include the eyes, upper face
(forehead and perinasal regions), hemifacial, and rare tongue
involvement (16,58,103,104,123). Tan et al. in their case
series reported the absence of spasms during sleep, lack of
worsening during voluntary facial movement and bilateral facial
contractions, with asynchronous contractions, and occasional
Frontiers in Neurology | www.frontiersin.org 10 February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
FIGURE 2 | Examples of functional dystonia phenomenology. Examples of functional dystonia phenomenology are shown: (A) functional cranial dystonia with bilateral
lip pulling; (B) functional blepharospasm with eyes tightly shut (left) and forcefully open when concentrating (right); (C) three examples of functional foot dystonia,
illustrating the typical posturing involving fixed dystonia with plantarflexion, inversion (left), in the same patient with extension of the great toe, with flexion of the others
toes (middle), and a different patient with paroxysmal dystonia involving plantarflexion and toe curling (right); (D) three examples of varying dystonic upper extremity
posturing in a patient with paroxysmal functional dystonia—right arm extended with wrist flexion and fisting (left), elbow flexion with wrist flexion akin to carpopedal
spasm (middle), and shoulder abduction, elbow flexion, and wrist flexion with a limp hand (right).
associated facial pain (104). Other features include alternating
spasms from one side of the face to the other and the presence of
very forceful spasms, lasting longer than typical hemifacial spasm
contractions (100). We have also observed frequent functional
sensory loss on the affected side. Another defining feature is the
absence of ipsilateral eyebrow elevation (the “other” Babinski
sign), typical of hemifacial spasm (16,124).
Functional blepharospasm is a rare entity, seen in 0.3–7%
of FMD (59,76) but is overall not an infrequent cause of
blepharospasm, accounting for 20% of a single-center series (125,
126). Other unusual features seen in functional blepharospasm,
include the presence of unusual visual symptoms and the
sudden onset of prolonged spasms, whereas in other forms of
blepharospasm, there is increased eyeblink rate slowly evolving
into more prolonged spasms (126). An example of a patient with
frequent, forceful eyelid spasm, which completely resolves when
concentrating and engaged is seen in Figure 2B.
Botulinum toxin injections, with or without facial physical
therapy (PT), are the treatment of choice for cranial OD. In FD,
patients may have an immediate response to botulinum toxin
injections, distinct from the delayed mechanism of action of
the toxin (16,127). On the other hand, cranial OD may have
gestes antagonistes, whereas these are frequently absent or highly
atypical in cranial FD, and in comparison to improvement of OD
symptoms touching the face, in FD, symptoms usually worsen
in response to touch (58,115). Furthermore, in comparison to
Frontiers in Neurology | www.frontiersin.org 11 February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
structural forms of hemifacial spasm, in functional spasm, there
is no evidence of vertebrobasilar dolichoectasia on magnetic
resonance angiography (104).
Cranial—Oromandibular/Tongue Dystonia
Oromandibular dystonia is a rare focal dystonia involving
abnormal involuntary contractions of the jaw, lower face, and
tongue and may interfere with speech and swallowing (128).
Jaw dystonia can be either predominantly jaw opening, closing,
or lateral deviation and is associated with muscular tension,
pain, spasms, and fatigue in the muscles of mastication and may
present initially as bruxism (129). Defazio et al. produced a set of
expert diagnostic recommendations, with core features including
that movements are patterned and repetitive and are either
spontaneous or triggered by certain motor tasks, with or without
associated tremor (130). In OD, jaw spasms are typically bilateral
(131). Talking and chewing typically worsen oromandibular
dystonia (129), however, in some cases there can be a paradoxical
improvement when talking or with adopting certain tongue
positions (105). In contrast, FD of the jaw typically involves
ipsilateral downward and lateral jaw pulling and other associated
signs including a fixed posture, ability to voluntarily suppress
the jaw movements/posture and the presence of distractibility
(103,130). In comparison, unilateral jaw dystonia is markedly
uncommon in OD (131). Oromandibular FD can migrate to
other non-adjacent sites or change in nature, such as jaw
movements with both opening and closing features that wax
and wane. Typically, OD and lingual dystonias, like most head
and neck dystonias, preserve vegetative tasks such as swallowing
and breathing, and a modified barium or video swallow
examination is helpful to document normal oropharyngeal
swallowing function. If pain is the predominant complaint, an
oral surgery consultation for evaluation for temporomandibular
disorders is helpful.
Tongue involvement is rare in OD (generally seen as part
of an oromandibular dystonia) and in FMD, is infrequently
seen in isolation, and is often associated with other body
involvement (126). Functional tongue dystonia is frequently
a tonic contraction and may commonly be associated with
functional tongue/facial weakness. In FD, there can be “wrong-
way” tongue deviation, with deviation toward the side of
apparent facial weakness (132). There may also commonly be
functional dyskinesias associated with the abnormal posture. A
clue toward a functional neurological diagnosis is the presence
of normal speech (speech should be dysarthric in the setting
of significant tongue dystonia), or stuttering speech (which
would be entirely inconsistent). Other indicators are resolution
of tongue involvement with testing individual speech sounds
(lingual, labial, and guttural) and holding prolonged vowel
sounds (“Ahh,” “Eee”), or even deep breathing, similar to that
seen in functional palatal tremor (120). The presence of full range
and normal active tongue movements despite deviation at rest
would also be incompatible with what would be seen in OD,
as such movements would generally trigger worsening dystonic
movements. We have also seen a case of functional tongue
dystonia/dyskinesia where the tongue movements entrained to
the direction of gaze when testing eye movements, which would
be incompatible with OD. Functional tongue dystonia may
respond to similar treatment involving retraining as functional
palatal tremor (133).
Suspected oromandibular and tongue dystonias should be
seen by an otolaryngologist. The workup and treatment strategies
for both FD and oromandibular OD include speech and
voice therapy, PT, behavioral strategies, and treatment for
temporomandibular joint disease including bite guards and a
soft diet. Botulinum toxin for jaw closing muscle groups, such
as the masseters, temporalis and pterygoids can have a positive
response, depending on the pattern of spasms. Injections to
the tongue, submandibular regions and anterior neck muscles
are associated with higher rates of swallowing side effects.
Response to therapy often helps differentiate FD from OD,
including appropriate response to botulinum toxin injections
and medications. Other strategies include muscle massage and a
soft diet, although being mindful of a view to transitioning over
time to a normal diet. Particularly in FD involving the tongue,
a video swallow evaluation may provide important information
regarding strategies to help prevent aspiration, regardless of the
cause, while speech therapy techniques involving retraining of
the tongue are important.
Functional Dysphonia Mimicking Spasmodic
Dysphonia
Spasmodic dysphonia (SD) is a focal primary dystonia involving
the laryngeal muscles which affect voice production. The
condition is more common in women and the vast majority are of
the adductor type, with a small proportion being of the abductor
type. The spasms may be accompanied by a dystonic tremor in
20% of cases, and respiratory involvement is rare but has been
described with adductor spasms occurring with breathing (134).
SD rarely can be task-specific, such as in singer’s dystonia (135).
Vegetative laryngeal tasks (such as breathing and swallowing) are
normal, with the primary symptoms involving voice production,
that often worsens with stress, phone use, vocal projection,
and public speaking. Sensory tricks can involve touching the
nose or chin, humming, laughing, singing, or normal emotional
laughing/crying (134). Adductor SD is characterized by vocal
strain, with roughness, voice breaks that sound and feel like
being strangled, and resulting difficulties with pitch regulation.
These voice changes are exacerbated during adductor laryngeal
tasks such as counting from 80 to 90. Abductor SD results in
involuntary spasms of the muscles that pull open the larynx with
a voice quality that sounds breathy, weak, and asthenic (134).
Abductor laryngeal tasks such as counting from 60 to 70 will
worsen these breathy breaks.
It is difficult to distinguish SD from functional dysphonia
mimicking SD. Therefore, patients should ideally be evaluated
by a skilled otolaryngologist and voice therapist with experience
in the assessment of functional voice disorders and SD, for
laryngoscopic evaluation. However, there are several clinical
clues, which can be useful for the practicing neurologist
(100,106). Baker provides an excellent review on features
differentiating purely functional speech, muscle tension
dysphonia (MTD) and other neurological causes of speech
disorders (107). In comparison to the rarity of abductor SD,
Frontiers in Neurology | www.frontiersin.org 12 February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
functional SD-like speech is frequently sudden in onset and
typically a breathy whisper, while some patients can present
with complete aphonia (100). Speech can be either high-pitched
(Minnie Mouse-esque), or low pitched and hoarse, there may
be occasional diplophonia (two vocal tones), and patients may
activate accessory facial, tongue and chest wall movements
in the struggling production of effortful speech (107). In FD,
vocal tremor is rare and is not associated with speech arrest
(100). The characteristic vocal cadence and rhythm for SD
that involves the sudden and intermittent, involuntary spasms
during adduction and abduction tasks are not consistently seen
in FD, where speech can be markedly variable. FD patients
frequently describe an associated globus sensation, which is
generally not reported in SD (107). Another hallmark, is that
normal or greatly improved phonation may generally not be
produced voluntarily but can be unconsciously produced, either
during reflex activities (coughing, laughing, yawning or with
excited/angry interjections), with other tasks, such as counting,
reciting, or singing, or with distraction facilitated by the assessor,
such as when performing a cognitive task in functional voice
disorders (107). In comparison, normal speech is not able to
be produced in SD during these tasks. Normal resonance in
functional dysphonia may also sometimes be produced when
the patient is asked to count as far as they can in a single breath,
generally on reaching the end of the breath.
The neck examination in functional dysphonia is often
notable for discomfort while palpating the thyrohyoid space and
cricothyroid space. In SD, the larynx is elevated and retracted,
and sometimes the thyroid notch is directly adjacent to the
hyoid bone, resulting in significant discomfort with manual
manipulation of the thyrohyoid space. An experienced voice
therapist can often differentiate between FD and SD based on the
clinical response from appropriate techniques directed at relaxing
and unloading laryngeal tension. In SD, laryngeal examination
reveals hyperkinetic activity, with excessive, exaggerated, and
involuntary vocal contractions, in either adductor or abductor
direction with voice production, but normal bilateral motion on
most other laryngeal tasks. Functional MTD laryngeal patterns
include sustained lateral or anterior-posterior hyperfunction of
the larynx, without the spasms, or severe hyperfunction at the
anterior vocal folds and false vocal folds, but with a persistent
open glottis. MTD can present with multiple laryngoscopic
voicing patterns that demonstrate vocal strain and uniform
hyperadduction of the vocal folds and supraglottis across voice
tasks (136). Further laryngoscopic characteristics suggestive of
a functional cause include the lack of a vocal tremor, no
phonetic variability, worsening at the end of a breath, constant
false vocal fold constriction and normal laryngeal structure and
function (106).
The treatment of functional dysphonia is centered around
voice therapy. Therapy techniques involve reducing vocal
strain, improving efficiency, and relaxing the laryngeal muscles.
Functional dysphonia can have a variety of presentations and it
takes a skilled and experienced voice therapist with persistence
and a large “toolbox” of techniques for success. Adjuvant medical
treatments for functional dysphonia can include sensory nerve
blocks, if there is a significant pain component to the spasms,
and botulinum toxin injections to weaken and rebalance muscle
groups. While botulinum toxin injections can help alleviate vocal
strain, the goal is to enable and improve voice therapy techniques.
Manual massage and masking can also be useful.
Cervical
Functional cervical dystonia often develops in response to trauma
or injury of the head, neck, or shoulder regions (58,94).
This form of FD generally occurs rapidly, is frequently painful
and immobilizing and may be associated with other abnormal
posturing in the body but cannot be explained by a specific
nerve injury (137). The most common form is post-traumatic
painful torticollis, frequently involving laterocollis and ipsilateral
shoulder elevation with contralateral shoulder depression (58).
In cervical FD, neck posturing may be frequently fixed, which is
highly atypical for OD but can be seen in neuroleptic-induced
cervical dystonia, where fixed extension (retrocollis) or flexion
(anterocollis) may occur (138). Another feature seen in cervical
OD is the “shirt collar sign,” where the shirt collar tends to be
shifted to one side (which appears related to the presence of
a cervical shift in the photographs presented by the authors),
whereas the shirt collar appears straight in FD (139). Cervical FD
can also be distinguished from OD by its frequent association
with pain, often out of proportion to the degree of posturing,
lack of effective sensory tricks (which are more common in
cervical than other forms of OD) and other comorbid functional
neurological symptoms (58,137). Treatment of both OD and
FD can involve targeted PT, while leveraging sensory tricks
and botulinum toxin injections are the mainstay of therapy
in OD. It is notable that targeted botulinum toxin injections
in some FD patients may yield benefit, particularly if there
is considerable objective muscle spasm and abnormal posture
(58). In comparison to FD, DBS can be used in cases of
pharmacologically refractory OD (140).
Paroxysmal
Paroxysmal OD typically arises early in life generally in
childhood or adolescence (141–143) and individuals presenting
with paroxysmal dystonia/dyskinesia above the age of 21
should broaden the differential diagnosis and clinicians should
consider a FMD as a possibility. Furthermore, while paroxysmal
dyskinesia and dystonia are very rare, these are common
phenotypes in FD. Paroxysmal FD is the most common
paroxysmal FMD, with paroxysmal events often presenting with
more than one form of FMD and with an average age of onset of
roughly 38.6 years (52). Paroxysmal FD manifests as frequently
sudden episodes or bursts of dystonic-appearing contractions,
which can affect virtually any region of the body, including the
limbs, trunk or face (16,144). Functional paroxysmal symptoms
can be differentiated from OD by their variability and frequent
inconsistency in semiology (16,52), as shown in Figure 2D. The
duration and frequency of episodes often widely fluctuates, as
well as the type and nature of the dystonic and/or dyskinetic
movements (16,52,144), and episodes may be triggered by, or
resolve in unusual or medically inexplicable ways (52,144). In
comparison, paroxysmal OD patients tend to have consistent,
stereotyped episodes, with similar episode durations. Despite
Frontiers in Neurology | www.frontiersin.org 13 February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
some ambiguity in cases of paroxysmal FD and our general
understanding of the disorder, some research suggests that
the prognosis for patients is relatively better than other FD
phenotypes (52).
PEDIATRIC FUNCTIONAL DYSTONIA
Pediatric FD has received relatively little study compared to
their adult counterparts, with few published case series, generally
in the setting of other FMDs (145). Similar symptoms, risk
factors, and patient histories tend to exist between FD and other
FMDs (146). Further research into and recognition of pediatric
FMDs and FD is especially important, particularly as symptoms
may be debilitating and frequently persist into adulthood (147,
148). As in adults, a shorter illness duration is predictive of a
better prognosis in FMD, while childhood functional somatic
symptoms can be a useful predictor for future mental and
physical health issues, including development of FND as an
adult (149).
In comparison to adults, FMD in children are felt to be
relatively rare (2–5 per 100,000 children) but involve 6–15%
of outpatient neurology diagnoses, although some of this may
be related to misdiagnosis (147). Studies indicate a mean age
of onset of 11–14 years (146,147,149) and is less common
below the age of 10 (very rare in some series) (146,148,150).
There have been some cases as young as age 3 reported (151),
although there is concern that at this age, the most common
cause may be behavioral. Sex is typically female, as is seen in
adult FMD, with girls more likely to develop FD, as opposed
to other forms of FMD (147). Of note, the proportion of
girls increases after adolescence, compared to a more equal sex
distribution in younger children (151). Some evidence suggests
that after symptom onset, the course tends to be more episodic
than is seen in adult patients (146,151). Compared to adult
FMD, children more frequently experience symptoms in their
dominant limb, and less frequently have an additional underlying
classical movement disorder (110,147). There have also been
episodes of “mass hysteria” with outbreaks of FMD in children
patterning the abnormal behaviors of their peers (152).
FD is a common manifestation of pediatric FMD and in
some case series, the most common phenotype seen (148).
Risk factors for pediatric FMDs are similar to those for adults,
such as high levels of environmental or social stress, comorbid
psychiatric disorders (anxiety greater than depression), and
precipitating traumatic events and injuries (145,147,148,153).
In children, trauma and stress typically manifest in the form
of familial stressors, including domestic violence and physical
abuse, separation from attachment figures, health issues in the
child or a family member, the presence of a parent with a
psychiatric disorder (146,147) and have low rates of sexual abuse
(although this may be related to reporting error) (145,151).
Precipitating factors in FD often involve a minor injury (of
which falls, a sting from an insect, jellyfish or an animal bite
have been described), in addition to a surgery or other medical
procedure (148). Other factors more exclusive to children include
recent vaccination, problems at school (including difficulties with
school work, bullying, or absenteeism), as well as participation
in competitive activities such as sports or ballet (145,151).
Disturbances during infancy, including trouble feeding, sleeping,
or reacting, may also signal future risk for functional somatic
symptoms later in childhood (149). Eating disorders have also
been reported to complicate pediatric fixed FD (154).
Pediatric FD often presents with fixed posturing
(15,147,148,154), and is frequently associated with pain
in the affected limb (15,146,154), or with sudomotor changes
consistent with CRPS-1 (154). As in adults, prolonged abnormal
posture can lead to contractures (122). Treating pediatric FD
patients must be handled delicately, as social factors contributing
to the disorder may be complex and sensitive for the child, and
treatments must be age-appropriate (15). Ideally, treatment is
multi-disciplinary and this can involving neurology, psychiatry,
relaxation techniques and breathing exercises, cognitive
behavioral therapy and tailored rehabilitation, including Mind-
Body programs (15,145). Hypnosis and meditation may also be
used to relax postures and alleviate stress (15,149). Pediatric FD
and FMD symptoms have sometimes resulted in unnecessary
surgeries, procedures and medication treatment (147), as well
as orthopedic surgeries to correct fixed posturing (154). Owing
to the frequently high severity of symptoms, FMDs frequently
impact academic performance at school and can be associated
with school absences, requiring home schooling in up to 50%
(147,148). Although a “diagnostic odyssey” is common in FMD
in general, this is especially the case in pediatric FD, where most
patients are extensively investigated (148,151).
ADJUNCTIVE DIAGNOSTIC TESTING IN
FUNCTIONAL DYSTONIA
Study of EMG has been utilized in research but is not yet
used clinically in the assessment of FD. In a study using
reaction time and co-contraction to attempt to differentiate
functional FD from OD, although FD patients tended to have
longer reaction times and lower levels of co-contraction during
voluntary movements, there was overlap between the two groups,
suggesting that even if these two parameters could be useful
in differentiating at a group level, they were not suitable for
diagnosis at the individual participant level (155). EMG has
also been advocated in pediatric FMD, with electrophysiology
being a supportive criterion of a functional origin in 4/5
patients with mixed FMD (146). Surface EMG can be a useful
adjunct to clinical examination (for instance electrophysiology
demonstrating distraction or entrainment) with some caution in
the setting of FD, given the overlap with OD. Using brainstem
evoked potentials, investigators compared the R2 blink reflex in
patients with atypical (presumed functional) blepharospasm and
other forms of blepharospasm and found that the R2 recovery
cycle was normal in functional blepharospasm but abnormal
in 9/10 of the other blepharospasm cases (156). This is an
interesting research observation but there is insufficient evidence
to recommend this clinically.
Other adjunctive maneuvers and strategies to contribute to
the clinical examination have been suggested. These include
Frontiers in Neurology | www.frontiersin.org 14 February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
the placebo immediate response to botulinum toxin injections
in fixed and other forms of FD (123) and the role of general
anesthesia (157), which can be useful in the diagnosis of complex
cases. The “swivel chair test,” where a patient propels himself
forwards and backwards on a swivel chair, was normal in
comparison to clearly impaired gait in 8 of 9 functional gait
patients (which may be frequently present in FD) but similarly
affected in other gait disorders (158). They did caution that in
patients with generalized dystonia, there may be a false positive
chair test, as this can serve as a geste antagoniste, resulting in
improvement, and as another limitation, there was no blinding
of the movement disorders neurologist performing the test (158).
Transcranial magnetic stimulation (TMS) has been
investigated to distinguish FD from OD. Reduced intracortical
inhibition and cutaneous silent period have been demonstrated
in both FD and OD (95,159,160), while in one study, forearm
spinal reciprocal inhibition was reduced only in FD (159).
However, there have been discrepancies in assessments of
cortical plasticity, which was noted to be abnormal only in
OD in one study (160), and in patients with CRPS-1, there
was also normal sensorimotor plasticity compared to controls.
However, cortical plasticity was abnormal bilaterally in both
OD and FD in another study, suggesting possible limitations
and less separation between diagnoses (161). In this study, the
presence of bilateral involvement despite unilateral dystonia
may suggest a trait/endophenotype rather than a consequence
of abnormal muscle contractions (161). The use of TMS in
dystonia is currently of research interest but could have future
clinical implications.
In comparison, intraoperative physiological recordings during
both thalamic and globus pallidus internus (GPi) DBS surgery
erroneously performed on patients with FD, firing rates and
thalamic reorganization were similar, while EMG coherence
and thalamic signal-to-noise ratio were different in FD and
OD, suggesting similarities and differences between these
disorders (162). However, in another study involving the
GPi, neurophysiology measures did not differentiate these
disorders (163).
“Laboratory supported criteria” for other FMD has been
suggested, and in areas with significant experience in the
evaluation of these disorders, may greatly add to helping verify
the diagnosis, particularly in challenging cases and hence reduce
unnecessary delay in diagnosis and subsequent unnecessary
workup (156,164). However, there are no straightforward tools
to apply to FD, and FD and OD share several neurophysiological
features, suggesting some associated pathophysiology. To date,
there are no or reliable discriminators for these disorders.
IMAGING AND THE PATHOPHYSIOLOGY
OF FUNCTIONAL DYSTONIA
Standard clinical imaging has been used to aid in differentiating
FMD from some other movement disorders. Excluding a
brain or spine lesion is performed when indicated by history,
physical examination, and investigations to rule out structural
pathology. In general, dystonia has normal imaging, although
certain forms of primary dystonia may show brain degeneration
and secondary dystonias can also have various abnormal
and sometimes pathognomonic imaging features [e.g., the
eye of the tiger” sign in neurodegeneration with brain iron
accumulation or the cerebral degeneration seen in X-linked
dystonia parkinsonism; (165)]. FD should also have normal
imaging, although there is always the possibility of an incidental
finding or a neurological comorbidity.
In neuroimaging research, Schrag et al. performed positron
emission tomography (PET) in 6 patients with fixed FD, 5
with DYT1 leg dystonia and controls at rest and during an
active motor task (166). At rest, while OD had increased
blood flow in the left primary motor cortex and thalamus
and decreased blood flow in the cerebellum; FD had opposite
findings, with increased cerebellum and basal ganglia and
decreased primary motor cortex blood flow (166). In comparison,
during the movement task, both OD and FD had abnormal
activation in the right dorsolateral prefrontal cortex (166). In
addition, a resting state study fMRI study in a mixed FMD
cohort (n=35; 43% with abnormal posturing) compared to
controls revealed decreased functional connectivity between the
right temporoparietal junction (TPJ) and sensorimotor cortices
after controlling for psychiatric comorbidity (167). The right
TPJ is believed to serve as a general comparator of internal
predictions/motor intentions with actual motor events, and is
implicated in impaired self-agency in FMDs (168).
Several studies have demonstrated abnormalities in brain
regions implicated in emotional processing in FD (169). Voon
et al. in 16 mixed FMD patients (2/16 with dystonia and 2/16
with multiple phenotypes including dystonia) found increased
functional connectivity between the right amygdala and the right
supplementary motor area when viewing affectively-valenced
faces (170). In another fMRI study of 10 patients with FMD
(FD n=2) exposed to emotionally-valenced images, there was
increased activity in the cerebellar-limbic network (cerebellar
vermis, posterior cingulate cortex, and hippocampus) involved in
processing emotional salience (171). Furthermore, Espay et al., in
an fMRI study of 12 patients with FD paired with 12 patients with
primary OD and 25 healthy controls, probed neural activation
profiles using a finger-tapping task (motor task), a basic emotion-
recognition task (emotional faces task), and an intense-emotion
stimuli task (172). During an emotional faces task, there was
decreased right middle temporal gyrus and bilateral precuneus
activation and increased activation in several brain regions
including the bilateral cerebellum in patients with FD compared
to the control groups; during an intense emotion processing task,
there was decreased left insula and motor cortex activations in FD
compared to OD, along with decreased right opercular and motor
cortex activations compared to both comparison groups (172).
There were no activation differences across groups in the motor
tasks (172). A separate resting state fMRI study of FD (n=40,
12 fixed and 28 mobile FD) revealed among other findings that
the entire dystonia group compared to healthy controls showed
increased connectivity between the left amygdala and bilateral
thalamus; additionally the dystonia cohort showed decreased
resting-state functional connectivity between the right TPJ and
dorsal and rostral prefrontal regions (173).
Frontiers in Neurology | www.frontiersin.org 15 February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
In a quantitative structural MRI study of 44 mobile (n=31)
and fixed FD (n=13) and 43 age-matched controls, mobile
FD revealed volume loss in gray matter structures (nucleus
accumbens, putamen, thalamus, caudate nuclei) compared to
controls, while compared to fixed FD, mobile FD revealed
hippocampal and globus pallidus atrophy (174). Individuals with
fixed FD also revealed white matter alterations in the corpus
callosum, corticospinal tract, anterior thalamic radiations, and
long-range tracts bilaterally compared to controls and mobile
FD (174). In a separate study of mixed FMD (35% FD), there
was increased volume in limbic circuitry (unilateral amygdala,
striatum, cerebellum, fusiform gyrus, and bilateral thalamus)
and decreased sensorimotor cortex volume, although these
volumetric profiles did not correlate with disease duration or
severity (175). These data suggest that FD is associated with
structural and functional brain network alterations, although
additional research is needed to investigate if these changes are
disease-related, compensatory, or related to comorbidities among
other possibilities (176).
Altered sensory processing has also been found to be
abnormal in FD. As a preliminary observation in 7 patients with
fixed dystonia, all noted a subjective abnormal perception of
the position of their ankle, feeling as if the ankle was straight
with eyes closed but when this was physically straightened by
an investigator, felt “abnormal” (119). Temporal discrimination
(time interval between two distinct stimuli to be recognized
as being separate from each other) has been found to be
abnormally prolonged in different forms of OD (177). In a
study of mental rotation and temporal discrimination in 11
patients with fixed FD and 11 mobile OD, OD revealed abnormal
temporal discrimination and mental rotation, while FD only
had abnormal mental rotation (178). It is also notable that
in a study of body identity disorder, there was also abnormal
rotation perception (179). However, in a study of temporal
discrimination threshold comparing FD with OD using paired
non-noxious electric shocks, this was abnormally long in both
groups compared to controls and there were no significant
differences between FD and OD, including when comparing the
affected and unaffected limbs (180).
MANAGEMENT OF FUNCTIONAL
DYSTONIA
Delivering the Diagnosis and
Communication in Functional Dystonia
Once the diagnosis of FD has been made, appropriately
communicating this to the patient is the first step in treatment
(181,182). Crucial to the treatment of FD is the patient’s
acceptance and understanding of the diagnosis. Functional
disorders in any organ system are frequently met with some
level of skepticism and stigma; patients may feel that their
diagnosis is “fake” and “all in their heads,” that their complaints
are not being met with serious consideration on the part
of the physician, or that treatment may be futile (64). The
sometimes uncertain and delegitimizing nature of the diagnosis
leads patients to “doctor shopping,” as patients seek alternative
opinions, not fully accepting their initial diagnosis and as a result
postponing appropriate treatment (64). Effective communication
while delivering the diagnosis facilitates patient understanding of
and receptiveness to their diagnosis (63). To deliver the diagnosis,
the clinician should emphasize that FND is real, common, brain-
based, and treatable, underscoring that the rationale behind the
diagnosis is based on neurological examination findings (12,182–
184). Providing education materials through websites such as
www.neurosymptoms.org or www.fndhope.org can be helpful.
The physician should also draw direct associations between
specific aspects of the treatment plan and the symptoms each
attempts to mitigate (185). We generally recommend not making
explicit links between FD symptoms and stress (unless the
patient is already doing this for themselves), given that while
these relationships may be important in some patients, they are
often indirect and nuanced (64,186). The term “functional”
is also preferred to “psychogenic” given that functional is an
etiologically neutral framing. Similarly, it can also be helpful
in early conversations to focus on “what” is the diagnosis
(based on examination), while the “why” can be explored by
the patient during the course of evidence-based treatment.
Prior to discussing a treatment plan with the patient, the
evaluating neurologist should determine the patient’s overall level
of acceptance (buy-in) to the diagnosis. For patients that are
very skeptical and seemingly rejecting of the diagnosis, it can
often be helpful to ask them to review materials online and to
return for a follow up visit to continue the discussion without
referring to specialized treatment (as doubts around the diagnosis
are likely to limit treatment engagement). Another issue that can
be a barrier to making the diagnosis and correctly and sensitively
relaying this to the patient is related to the provider’s own views
on FND, which colors the entire perspective of this condition
(187). Fortunately, with greater awareness, understanding and
acceptance of FND as a legitimate diagnosis, these views are
slowly changing, to the betterment of patients. For those that are
receptive to the diagnosis, the sections below discuss available
evidence-based treatments.
Multidisciplinary Treatment of Functional
Dystonia
Optimal FMD treatment is multidisciplinary, involving input
from neurologists, psychiatrists, physical, occupational, speech
and language and psychotherapists, and others, as necessary
(183). Medication, including botulinum toxin injections, and
pharmacological treatments for underlying psychiatric disorders
may also provide some benefit (183–185). In cases where those
primary treatment methods do not sufficiently resolve symptoms,
other specialized forms of rehabilitation may be considered,
including hypnosis, assessment under anesthesia, or electrical
nerve stimulation (183,184).
Physical rehabilitation is vital for the treatment of FD and
other FMDs (184). Across several surveys of neurologists, ∼80%
concurred that PT was a key component in an effective FMD
treatment plan (63,185,188) and 60–70% of FMD patients
experience some improvement of symptoms with PT (184).
FD patients require a range of different rehabilitative methods,
Frontiers in Neurology | www.frontiersin.org 16 February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
reinforcing understanding of their diagnosis through exercises
and practice. Patients should be given a graded home exercise
program, surpassing each stage once physically capable until
they reach effectively normal movement (185). Another tenet
of therapy involves demonstration of normal movements by
the physician or therapist, and positive reinforcement of those
normal movements in the patient (184). The distractibility of
certain FMDs can also be harnessed to retrain normal movement
via simultaneous cognitive or motor tasks, and the role of
attention and distraction can be explicitly discussed with the
patient as part of the therapeutic process (184). Physical activity
and meeting rehabilitation goals has also been shown to have
positive psychosocial effects on patients with FMDs, which is
particularly significant for patients with poor social or emotional
environments or psychiatric illness such as anxiety or depression
(189). Furthermore, special attention should be given to teaching
awareness of the patient’s contractions and posturing so the
patient may voluntarily counteract them, such as by resting a limb
on a weight-bearing surface (184).
Physical Therapy for Functional Dystonia
Evidence supporting PT as an integral component of a
multimodal treatment approach for functional neurological
disorders has amassed over the last half century (185,190–
194). In 2015, a group of clinicians with experience in
treating FND developed consensus recommendations to
guide PT treatment (184). The authors recommend a program
incorporating four principal components: Nielsen et al. (185)
education to enhance the patient’s understanding of FND,
Trieschmann et al. (190) demonstration that normal movements
can occur, Ness (191) retraining movements with diverted
attention, and Speed (192) changing maladaptive behaviors
that provoke symptoms. Additionally, the literature supports
treatment progressions that are both individualized and
consistent with progressions for similar neurologic conditions.
For example, if the patient is having difficulty standing,
postural-control training may be initiated in a supported
standing position, allowing normal elements of postural
control to occur. Positive responses are identified, practiced,
and reinforced.
Unfortunately, there is little to no reporting in the literature
with respect to specific physical interventions for treatment of
FD; this includes that the intensity and duration of physical
therapy for FD and related FMDs has yet to be operationalized
(195,196). In treating FD, the therapist uses similar strategies as
those used when managing OD, while incorporating principles
consistent with the consensus recommendations. Posturing
of a limb or body part associated with a focal dystonia
may be reduced by changing the nature of the task causing
the dystonia or by altering the patient’s posture relative to
gravity to identify positions in which the patient can begin
to move the affected body part (see Table 4). Research in
motor learning supports the use of external targets to designate
the direction and amplitude of the desired movement (197).
The use of mirrors or direct visualization of newly gained
positions or movement may help to resolve the discrepancy
in perceived vs. actual joint or body part posturing (119).
Once positive change in muscle tension or posturing is
identified, the patient is encouraged to utilize that position to
activate the desired movements and to practice them daily.
As the patient demonstrates mastery, the amplitude of the
movements is increased, and then the position in which the
patient generates the movements is progressed until they can
be performed against gravity and within the scope of each
desired movement.
The use of orthotic devices and/or adaptive equipment is
discouraged, as it brings unwanted attention to the involved
body part or dysfunction. Splinting or bracing may be used to
prevent joint injury or damage but should be done so judiciously,
and weaned as quickly as possible. Likewise, the use of canes,
walkers, or other adaptive equipment should be used to promote
ambulatory function (for example—to facilitate a safe discharge
from the hospital) but removed once safe ambulation has been
restored. Examples of PT approaches and their rationale are
shown in Table 4.
Occupational Therapy for Functional
Dystonia
Occupational therapists (OTs) have been identified as an integral
member of the multidisciplinary team in the care of patients
with FND (198), including FD (15). Given training in mental
health and expertise in using meaningful activities to engage
patients and increase participation, OTs are well-aligned to
aide these patients in managing symptoms, developing coping
strategies, changing behaviors, and improving function. Until
recently, there has been little in the literature regarding OT
assessment and treatment to guide clinicians in the treatment
of FND and FD. Nicholson et al. recently published consensus
guidelines for the occupational therapy assessment and treatment
of FND (199). Interventions used with patients who have FD
are provided within these guidelines, including the following:
encouragement of normal posture and movement through use
of distractions (i.e., physical and cognitive), eliciting automatic
movement (i.e., weight bear in quadruped, ball toss, etc.),
changing posture/positions while performing an activity (i.e.,
work within gravity eliminated positions, avoiding prolonged
postures at end ranges of motion), and developing and
implementing a balanced daily schedule to ensure graded re-
introduction into daily living skills (199). Splinting should be
used cautiously (nighttime splint only) as to reduce risk for
non-use of the limb.
Outpatient OTs at MGH have experienced some success in
the treatment of FD using guidance from current literature. The
treatment approach uses a combination of interventions based
on FND guidelines to treatment such as diverting attention to
normalize movement patterns (184,199), in conjunction with
interventions for focal OD (200,201). These can include motor
retraining through use of mental imagery, visualization and
mirror therapy and sensory retraining, by having the patient
palpate and identify raised letters of the alphabet, find coins in
a container of rice, or put shapes into matching holes. These
retraining techniques can also be considered as use of distraction
Frontiers in Neurology | www.frontiersin.org 17 February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
TABLE 4 | Physical therapy approaches in functional dystonia.
PT intervention Examples Rationale
Distraction
strategies
- Counting steps out loud while walking
- Counting backwards by 3’s
- Naming fruits that begin with sequential letters of the alphabet
Distraction reduces the focus of the central nervous system on the altered
posture/movement
Change
posture/position
- LE - Supine, Prone knee extended, Prone knee flexed
- Cervical - Supine, Prone, Semi-recumbent
Changing the body or limb posture relative to gravity alters sensory input
and can minimize abnormal posturing allowing for active movement
Weight bearing
through extremity
- Sitting with foot on an incline in some plantar flexion
- Sitting with foot on a ball
- Standing with UE or trunk support
Changing the sensory input of the extremity can alter the motor output
Graded task
performance
- Begin with whatever movement the individual can perform actively,
opposite the preferred posture
Begin slowly with goals for performance set in conjunction with the patient
to promote intrinsic motivation. Gradually incorporate segmental limb
movements then full body using functional tasks
Elicit automatic
movements
- Generate postural control reactions in sitting and standing that
engage head and neck for cervical dystonia and the LE for
LE dystonia
- Walking quickly, walking backwards or running may reduce
altered posturing
Reflexive and automatic movements are often retained and can be used
to demonstrate to the individual that typical movement is available.
Increasing speed of movement might reduce posturing
Sensory - motor
retraining
- Direct visualization of normalized movement
- Use of mirrors for visualization of improved body posture
Actual vs. perceived body/limb/joint posture might be disparate.
Visualization helps reduce the disparity
Interventions to
avoid
- Passive stretching Attempting to alter the posturing passively may result in increased muscle
contraction of already overactive muscles
- Orthotic devices/adaptive equipment The goal is to reduce attention to the altered posture or movement
Additional
considerations
- Promote a schedule of daily activity. Start at a level the individual can
achieve and increase slowly every few days
Altered postures and difficulty moving can result in reduced activity levels
UE, upper extremity; LE, lower extremity.
exercise to enhance the sensory and motor systems for re-
education and encourage normal movement patterns. Examples
of OT strategies are found in Table 5.
Patients with FND and FD are often impacted by
psychological co-morbidities and pain. Ranford et al. have
found that patients with FND often endorse sensory processing
difficulties that are commonly seen in patients with anxiety and
post-traumatic stress disorder (96,202). They suggest obtaining
a sensory profile of patients with FND to assist with developing
interventions. There are multiple approaches to treating sensory
modulation dysfunction in the literature. Examples include
promoting daily self-regulation through implementation of
sensory strategies/experiences (i.e., fidget with stress ball,
eat strong tasting mint, use weighted blanket, or pulling a
resistance band) and training use of coping strategies such as
progressive muscle relaxation, diaphragmatic breathing, and
guided meditation (203,204). Incorporating these sensory-based
interventions may enhance patient recovery when provided in
combination with other available treatments.
It is important to develop concrete goals and measure
progress, as their symptoms may not change, however
functionally individuals may make gains. To aid in documenting
clinical change, there are several outcome measurement tools
which can be found in the OT consensus guidelines (199).
Development of an individualized treatment plan based on
functional goals may assist to maximize patient outcomes.
Other Treatment Approaches
Patients with speech or swallowing symptoms may benefit from
targeted speech and language pathology input, particularly for
oromandibular and other cranial FD, or if these form part
of the symptom complex, using approaches similar to that of
PT and OT (205). The use of cognitive behavioral therapy
(CBT) to examine relationships between FD symptoms, thoughts,
behaviors, emotions and life factors is generally also considered
an emerging first line treatment for FD and related FMDs
(although more research including larger scale randomized
controlled trials are needed) (206,207). Psychotherapy can
also help address psychological trauma and other stressful
events or environments that may have contributed to the
onset of FD (58). The self-guided CBT workbook, “Overcoming
Functional Neurological Symptoms: A Five Area Approach,”
based on the clinical trial by Sharpe and colleagues, can be a
helpful recommendation; in our clinical program, we generally
recommend that this workbook can be used as a guide in the
course of individual psychotherapy (208). Psychopharmacology
may also be beneficial, primarily to address comorbidities
which may be perpetuating factors (209). However, given
somatic hypervigilance that can be found in some patients
with FD and related FMDs, it may be advisable to first ensure
that the patient is connecting to physical rehabilitation and
psychotherapy recommendations before secondarily re-visiting
psychotropic medication treatment. That being said, for patients
with high acuity (and active) psychiatric comorbidities, it is
advisable to involve a psychiatrist early in the assessment
process for active management of psychiatric comorbidities.
Particularly severe cases may also benefit from inpatient
treatment, as part of a specific inpatient multidisciplinary
treatment protocol (210).
Examination under sedation is also uniquely useful in cases
of fixed functional dystonia, as relaxation under anesthesia
(whether general or local anesthesia) suggests reversibility of
Frontiers in Neurology | www.frontiersin.org 18 February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
TABLE 5 | Occupational therapy approaches in functional dystonia.
OT Intervention Examples Rationale
Distraction strategies - Promote normal movement through use of physical (i.e.,
manipulate item in hand) and cognitive (i.e., counting backwards
from 100 by 3) strategies
Distraction reduces the focus on the altered posture/movement
Change posture/position - Use gravity eliminated positions to achieve improved
performance with functional tasks and posture at rest
- Avoid prolonged postures at end ranges of motion
Changing the body or limb posture relative to gravity alters sensory
input and can minimize abnormal posturing allowing for active
movement
Graded task performance - Focus on reintegration of affected limb with activity-based
functional tasks
Begin slowly with goals for performance set in conjunction with the
patient to promote intrinsic motivation. Gradually incorporate
segmental limb movements then full body using functional tasks
Elicit automatic movement - Ball toss, weight bearing in quadruped, sit on therapy ball Reflexive and automatic movements are often retained and can be
used to demonstrate to the individual that typical movement is
available. Increasing speed of movement might reduce posturing
Motor retraining - Mirror therapy
- Visualization
- Mental Imagery
Actual vs. perceived body/limb/joint posture might be disparate.
Visualization helps reduce the disparity
Sensory retraining With eyes closed:
- Palpate and identify raised letters of alphabet
- Use limb to search for coins in rice
- Put shapes into matched holes
Actual vs. perceived body/limb/joint posture might be disparate.
Visualization helps reduce the disparity
Coping strategies - Guided meditation
- Progressive muscle relaxation
- Diaphragmatic breathing
Patient’s ability to handle stress and anxiety and providing
technique to allow relaxation of muscles
Sensory modulation
training
- Explore and use different sensory tools based on preference (i.e.,
eating strong tasting mint/candy, weighted blanket, etc.)
- Develop and use a Sensory Diet (planned use) to facilitate
self-awareness of positive change
To assist with process of regulating specific behavioral responses
to sensory stimuli
Interventions to avoid/limit
use of
- Splinting to prevent non-use of limb
- Adaptive aids
- May consider use at rest (i.e., positional splint while sleeping)
Attempting to alter the posturing passively may result in increased
muscle contraction of already overactive muscles
The goal is to reduce attention to the altered posture or movement
and not provide reliance on aids
Additional considerations - Develop functional goals vs. symptom-based goals
- Encourage normal movements through participation in
functional activities
Altered postures and difficulty moving can result in reduced activity
levels and to promote normal activity where possible
symptoms, and can even be therapeutic (184): in one study,
5 out of 11 patients who did not respond to other treatments
showed major improvements after anesthesia (183). A subset
of FD patients may also respond to botulinum toxin injections,
either as a placebo response, or by reducing tension in tonically
activated muscles associated with fixed postures; however, unlike
in OD, response may be immediate, which is not compatible
with the pharmacological effect, which begins after a few days,
typically peaking at 2 weeks (183,211). While use of targeted anti-
depressant or anxiolytic treatment, or treatment of neuropathic
pain may be beneficial in FD, other typical medications used in
the treatment of dystonia (benzodiazepines, trihexyphenidyl and
other anti-cholinergics, or carbidopa/levodopa) and certainly
DBS, should be avoided in FD (212,213). Such treatments
can have placebo effects but their potential risks far outweigh
any benefits.
PROGNOSIS IN FUNCTIONAL DYSTONIA
The prognosis for patients with FD is unfortunately generally
poor (11). It is not uncommon for patients to experience
no improvement in distress or functional impairment even
after multiple courses of treatment (58,79). Patients may also
experience fluctuation in the severity of their symptoms, with
only short-lived remissions (211). In some cases, treatment is
altogether unsuccessful and symptoms can be progressive and
debilitating (211,214) and as many as 31% of patients may
have worsening symptoms following treatment (211). Worse
outcomes are particularly associated with the presence of chronic
pain and CRPS (211). In a study assessing prognosis in fixed
dystonia, there were higher levels of comorbid depression and
somatic symptoms in those who had unchanged or worse
symptoms on follow-up (211). Patient satisfaction with their
physician also contributes to their outcomes (79); a retrospective
study on FMD prognosis (40% FD), 22.1% noted worse
outcomes, with patient dissatisfaction noted as a significant factor
(214). There is also inconsistency and disagreement regarding
how to assess patient outcomes in FD and other FMD, making
it challenging objectively quantify treatment response and may
result in suboptimal treatment (215).
Despite poor or variable responses to treatment, certain
patients do improve, and in some cases undergo complete
remission (79,214). In a retrospective study assessing prognosis
in FMD, 56.6% reported symptomatic improvement, while
43.4% had either no change or progression (214). Such positive
outcomes in FMD have been associated with better physical and
Frontiers in Neurology | www.frontiersin.org 19 February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
social health, as well as an overall shorter duration of illness
(79,214). In comparison, in a study of 35 fixed FD patients, 23%
improved but only 6% had major remissions (211). Given a lack
of a gold standard of management in patients, despite consensus
guidelines, treatment must be individualized, tailored to the
type of physical symptoms, and level of psychiatric comorbidity,
with physical rehabilitation, psychotherapy and management of
comorbidities as the primary components of the therapeutic
multidisciplinary approach (183).
CONCLUSIONS
FD is a diagnostically challenging and frequently debilitating
subtype of FMD that can present in many different forms.
Recognition of a FND in a patient presenting with dystonia
symptoms is of paramount importance and we include
a comprehensive appraisal of clinical clues and historical
indicators of an FD diagnosis to help the practicing clinician.
Adjunctive neurophysiological and other testing do not reliably
differentiate FD from OD. A multidisciplinary approach,
tailored to the patient, including neurology, psychiatry, PT, OT,
speech therapy, and psychotherapeutic approaches is frequently
required, in addition to possible use of botulinum toxin
injections, other pharmacological approaches, and inpatient
rehabilitation programs. Our understanding regarding the nature
of FD and particularly post-traumatic dystonia is still evolving.
Early diagnosis and treatment may help prevent unnecessary
investigations and procedures, while facilitating the appropriate
management of these highly complex patients.
AUTHOR CONTRIBUTIONS
LF: first draft of manuscript and acquisition of data. DP and
NS: analysis and interpretation, and critical revision of the
manuscript for important intellectual content. JC, JM, and PS:
acquisition of data, analysis and interpretation, and critical
revision of the manuscript for important intellectual content. CS:
study concept and design, first draft of manuscript, acquisition
of data, analysis and interpretation, and critical revision of
the manuscript for important intellectual content. All authors
contributed to the article and approved the submitted version.
PERMISSIONS
Signed consent for the publishing of photographs was acquired
for the use of all anonymous patient images in Figure 2.
SUPPLEMENTARY MATERIAL
The Supplementary Material for this article can be found
online at: https://www.frontiersin.org/articles/10.3389/fneur.
2020.605262/full#supplementary-material
REFERENCES
1. Albanese A, Bhatia K, Bressman SB. Phenomenology and classification
of dystonia: a consensus update. Mov Disord. (2013) 28:863–73.
doi: 10.1002/mds.25475
2. Ballint B, Mencacci NE, Valente EM, Pisani A, Rothwell J,
Jankovic J, et al. Dystonia. Nat Rev Dis Primers. (2018) 4:1–23.
doi: 10.1038/s41572-018-0039-y
3. Nutt JG, Muenter MD, Aronson A, Kurland LT, Melton LJ III. Epidemiology
of focal and generalized dystonia in Rochester, Minnesota. Mov Disord.
(1988) 3:188–94. doi: 10.1002/mds.870030302
4. Defazio G. The epidemiology of primary dystonia: current
evidence and perspectives. Eur J Neurol. (2010) 17(Suppl. 1):9–14.
doi: 10.1111/j.1468-1331.2010.03053.x
5. Jinnah HA, Neychev V, Hess EJ. The anatomical basis for dystonia:
the motor network model. Tremor Other Hyperkinet Mov. (2017) 7:506.
doi: 10.5334/tohm.383
6. Klein C, Lohmann K, Marras C, Münchau A. Hereditary dystonia overview.
In: Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJH, Stephens K,
Amemiya A, editors. GeneReviews R
[Internet]. Seattle, WA: University of
Washington, Seattle; 1993-2020 (2003). p. 1–26.
7. Alterman RL, Filippidis AS. Genetic subtypes and deep brain stimulation in
dystonia. Mov Disord Clin Pract. (2018) 5:357–60. doi: 10.1002/mdc3.12660
8. Artusi CA, Dwivedi A, Romagnolo A, Bortolani S, Marsili L, Imbalzano
G, et al. Differential response to pallidal deep brain stimulation among
monogenic dystonias: systematic review and meta-analysis. J Neurol
Neurosurg Psychiatry. (2020) 91:426–33. doi: 10.1136/jnnp-2019-322169
9. Stephen CD, Go CL, Acuna P, Sharma N. Phasic knee bending dystonic and
parkinsonian gait: a characteristic finding in x-linked dystonia parkinsonism.
Mov Disord Clin Pract. (2020) 7:448–52. doi: 10.1002/mdc3.12929
10. Newby RE, Thorpe DE, Kempster PA, Alty JE. A history of dystonia:
ancient to modern. Mov Disord Clin Pract. (2017) 4:478–85.
doi: 10.1002/mdc3.12493
11. Newby R, Alty J, Kempster P. Functional dystonia and the borderland
between neurology and psychiatry: new concepts. Mov Disord. (2016)
31:1777–84. doi: 10.1002/mds.26805
12. Stephen CD, Sharma N, Callahan J, Carson AJ, Perez DL. A case
of functional dystonia with associated functional neurological
symptoms: diagnostic and therapeutic challenges. Harv Rev
Psychiatry. (2017) 25:241–51. doi: 10.1097/HRP.0000000000
000135
13. Perez DL, Keshavan MS, Scharf JM, Boes AD, Price BH. Bridging the great
divide: what can neurology learn from psychiatry? J Neuropsychiatry Clin
Neurosci. (2018) 30:271–8. doi: 10.1176/appi.neuropsych.17100200
14. Espay AJ, Aybek S, Carson A, Edwards MJ, Goldstein LH,
Hallett M, et al. Current concepts in diagnosis and treatment of
functional neurological disorders. JAMA Neurol. (2018) 75:1132–41.
doi: 10.1001/jamaneurol.2018.1264
15. Khachane Y, Kozlowska K, Savage B, McClure G, Butler G, Gray
N, et al. Twisted in pain: the multidisciplinary treatment approach
to functional dystonia. Harv Rev Psychiatry. (2019) 27:359–81.
doi: 10.1097/HRP.0000000000000237
16. Ganos C, Edwards MJ, Bhatia K. The phenomenology of functional
(psychogenic) dystonia. Mov Disord Clin Pract. (2014) 1:36–44.
doi: 10.1002/mdc3.12013
17. Trimble M, Reynolds EH. A brief history of hysteria: from the
ancient to the modern. Handb Clin Neurol. (2016) 139:3–10.
doi: 10.1016/B978-0-12-801772-2.00001-1
18. Marsden CD, Harrison MJ, Bundey S. Natural history of idiopathic torsion
dystonia. Adv Neurol. (1976) 14:177–87.
19. Fahn S, Eldridge R. Definition of dystonia and classification of the dystonic
states. Adv Neurol. (1976) 14:1–5.
20. van Rooijen DE, Geraedts EJ, Marinus J, Jankovic J, van Hilten
JJ. Peripheral trauma and movement disorders: a systematic review
of reported cases. J Neurol Neurosurg Psychiatry. (2011) 82:892–8.
doi: 10.1136/jnnp.2010.232504
Frontiers in Neurology | www.frontiersin.org 20 February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
21. Munts AG, Koehler PJ. How psychogenic is dystonia? Views from past to
present. Brain. (2010) 133(Pt 5):1552–64. doi: 10.1093/brain/awq050
22. Klein C, Fahn S. Translation of Oppenheim’s 1911 paper on dystonia. Mov
Disord. (2013) 28:851–62. doi: 10.1002/mds.25546
23. Duchenne G. De L’électrisation Localisée Et De Son Application A La
Pathologie Et A La Thérapeutique. Paris: J. B. Baillière (1861). p. 918–46.
24. Bogousslavsky J. Sigmund Freud’s evolution from neurology to psychiatry:
evidence from his La Salpêtrière library. Neurology. (2011) 77:1391–4.
doi: 10.1212/WNL.0b013e31823152a1
25. Tomlinson W. Freud and psychogenic movement disorders. In: Hallett M,
Fahn S, Jankovic J, Lang AE, Cloninger CR, Yudofsky SC, editor. Psychogenic
Movement Disorders. Philadelphia, PA: AAN Press (2006). p. 14–9.
26. Stone J. Neurologic approaches to hysteria, psychogenic and functional
disorders from the late 19th century onwards. Handb Clin Neurol. (2016)
139:25–36. doi: 10.1016/B978-0-12-801772-2.00003-5
27. Stiefel J. Blinding hysterical blepharospasm treated with
pipradol hydrochloride. Am J Psychiatry. (1966) 122:1294–5.
doi: 10.1176/ajp.122.11.1294
28. Meares R. Spasmodic torticollis. Aust N Z J Psychiatry. (1973) 7:3–5.
doi: 10.3109/00048677309161469
29. Stone J, Carson A, Sharpe M. Functional symptoms in neurology:
management. J Neurol Neurosurg Psychiatry. (2005) 76(Suppl. 1):i13–21.
doi: 10.1136/jnnp.2004.061663
30. Eldridge R, Riklan M, Cooper IS. The limited role of psychotherapy
in torsion dystonia. Experience with 44 cases. JAMA. (1969) 210:705–8.
doi: 10.1001/jama.210.4.705
31. Cooper I. Dystonia musculorum deformans: natural history
and neurosurgical alleviation. J Pediatr. (1969) 74:585–92.
doi: 10.1016/S0022-3476(69)80042-9
32. Denny-Brown D. The nature of dystonia. Bull NY Acad Med. (1965) 41:858–
69.
33. Marsden C. The problem of adult-onset idiopathic torsion dystonia
and other isolated dyskinesias in adult life (including blepharospasm,
oromandibular dystonia, dystonic writer’s cramp, and torticollis, or axial
dystonia). Adv Neurol. (1976) 14:259–76.
34. Lesser RP, Fahn S. Dystonia: a disorder often misdiagnosed as a
conversion reaction. Am J Psychiatry. (1978) 135:349–52. doi: 10.1176/ajp.
135.3.349
35. Berman BD, Junker J, Shelton E, Sillau SH, Jinnah HA, Perlmutter JS,
et al. Psychiatric associations of adult-onset focal dystonia phenotypes. J
Neurol Neurosurg Psychiatry. (2017) 88:595–602. doi: 10.1136/jnnp-2016-
315461
36. Batshaw ML, Haslam RH. Multidisciplinary management of dystonia
misdiagnosed as hysteria. Adv Neurol. (1976) 14:367–73.
37. Malpractice against psychologist, pediatrician neurologist–dystonia
musculorum deformans–direct cross-examination of plaintiff’s expert (a
neurosurgeon)–part I. Med Trial Tech Q. (1977) 24:83–120.
38. Fahn S, Williams D, Reches A, Lesser RP, Jankovic J, Silberstein S. Hysterical
dystonia, a rare disorder: report of five documented cases. Neurology. (1983)
33(Suppl. 2):161. doi: 10.1212/WNL.33.10.1255
39. Fahn S, Williams DT. Psychogenic dystonia. Adv Neurol. (1988) 50:431–55.
40. Espay A, Lang A. Phenotype-specific diagnosis of functional (psychogenic)
movement disorders. Curr Neurol Neurosci Rep. (2015) 15:32.
doi: 10.1007/s11910-015-0556-y
41. Morgante F, Edwards MJ, Espay AJ, Fasano A, Mir P, Martino D. Diagnostic
agreement in patients with psychogenic movement disorders. Mov Disord.
(2012) 27:548–52. doi: 10.1002/mds.24903
42. van der Salm SM, de Haan RJ, Cath DC, van Rootselaar AF, Tijssen MA. The
eye of the beholder: inter-rater agreement among experts on psychogenic
jerky movement disorders. J Neurol Neurosurg Psychiatry. (2013) 84:742–7.
doi: 10.1136/jnnp-2012-304113
43. Edwards MJ, Stone J, Lang AE. From psychogenic movement disorder to
functional movement disorder: it’s time to change the name. Mov Disord.
(2014) 29:849–52. doi: 10.1002/mds.25562
44. Perez DL, Aybek S, Nicholson TR, Kozlowska K, Arciniegas DB,
LaFrance WC Jr. Functional neurological (conversion) disorder: a core
neuropsychiatric disorder. J Neuropsychiatry Clin Neurosci. (2020) 32:1–3.
doi: 10.1176/appi.neuropsych.19090204
45. Cubo E, Hinson VK, Goetz CG, Ruiz PG, Garcia de Yebenes J, Marti MJ, et al.
Transcultural comparison of psychogenic movement disorders. Mov Disord.
(2005) 20:1343–5. doi: 10.1002/mds.20561
46. Kamble N, Prashantha DK, Jha M, Netravanthi M, Janardhan Reddy YC,
Pal PK. Gender and age determinants of psychogenic movement disorders:
a clinical profile of 73 patients. Can J Neurol Sci. (2016) 43:268–77.
doi: 10.1017/cjn.2015.365
47. Batla A, Stamelou M, Edwards M, Pareés I, Saifee TA, Fox Z, et al. Functional
movement disorders are not uncommon in the elderly. Mov Disord. (2013)
24:540–3. doi: 10.1002/mds.25350
48. McKee K, Glass S, Adams C, Stephen CD, King F, Parlman
K, et al. The inpatient assessment and management of motor
functional neurological disorders: an interdisciplinary perspective.
Psychosomatics. (2018) 59:358–68. doi: 10.1016/j.psym.2017.
12.006
49. Stamelou M, Cossu G, Edwards MJ, Murgia D, Pareés I, Melis M, et al.
Familial psychogenic movement disorders. Mov Disord. (2013) 28:1295–8.
doi: 10.1002/mds.25463
50. Lungu C, Ozelius L, Standaert D, Hallett M, Sieber BA, Swanson-Fisher C,
et al. Defining research priorities in dystonia. Neurology. (2020) 94:526–37.
doi: 10.1212/WNL.0000000000009140
51. Risch N, de Leon D, Ozelius L, Kramer P, Almasy L, Singer B, et al.
Genetic analysis of idiopathic torsion dystonia in Ashkenazi Jews and their
recent descent from a small founder population. Nat Genet. (1995) 9:152–9.
doi: 10.1038/ng0295-152
52. Ganos C, Aguirregomozcorta M, Batla A, Stamelou M, Schwingenschuh P,
Münchau A, et al. Psychogenic paroxysmal movement disorders– clinical
features and diagnostic clues. Parkinsonism Relat Disord. (2014) 20:41–6.
doi: 10.1016/j.parkreldis.2013.09.012
53. Gardiner AR, Jaffer F, Dale RC, Labrum R, Erro R, Meyer E, et al. The clinical
and genetic heterogeneity of paroxysmal dyskinesias. Brain. (2015) 138(Pt
12):3567–80. doi: 10.1093/brain/awv310
54. Latorre A, Bhatia KP. Treatment of paroxysmal dyskinesia. Neurol Clin.
(2020) 38:433–47. doi: 10.1016/j.ncl.2020.01.007
55. Tomic A, Petrovic I, Pesic D, Voncina MM, Svetel M, Miskovic
ND, et al. Is there a specific psychiatric background or personality
profile in functional dystonia? J Psychosom Res. (2017) 97:58–62.
doi: 10.1016/j.jpsychores.2017.04.004
56. Martino D, Brander G, Svenningsson P, L arssonH, de la Cruz LF. Association
and familial coaggregation of idiopathic dystonia with psychiatric outcomes.
Mov Disord. (2020) 35:2270–8. doi: 10.1002/mds.28257
57. Mulroy E, Balint B, Bhatia KP. Tardive syndromes. Pract Neurol. (2020)
20:368–76. doi: 10.1136/practneurol-2020-002566
58. Schmerler DA, Espay AJ. Functional dystonia. Handb Clin Neurol. (2016)
139:235–45. doi: 10.1016/B978-0-12-801772-2.00020-5
59. Williams DT, Ford B, Fahn S. Phenomenology and psychopathology related
to psychogenic movement disorders. Adv Neurol. (1995) 65:231–57.
60. Hallett M. Physiology of psychogenic movement disorders. J Clin Neurosci.
(2010) 17:959–65. doi: 10.1016/j.jocn.2009.11.021
61. Baizabal-Carvallo JF, Hallett M, Jankovic J. Pathogenesis and
pathophysiology of functional (psychogenic) movement disorders. Neurobiol
Dis. (2019) 127:32–44. doi: 10.1016/j.nbd.2019.02.013
62. Daum C, Gheorghita F, Spatola M, Stojanova V, Medlin F, Vingerhoets
F, et al. Interobserver agreement and validity of bedside ’positive
signs’ for functional weakness, sensory and gait disorders in conversion
disorder: a pilot study. J Neurol Neurosurg Psychiatry. (2015) 86:425–30.
doi: 10.1136/jnnp-2013-307381
63. Espay AJ, Goldenhar LM, Voon V, Schrag A, Burton N, Lang AE.
Opinions and clinical practices related to diagnosing and managing
patients with psychogenic movement disorders: an international survey
of movement disorder society members. Mov Disord. (2009) 24:1366–74.
doi: 10.1002/mds.22618
64. Hallett M. Psychogenic movement disorders: a crisis for neurology.
Curr Neurol Neurosci Rep. (2006) 6:269–71. doi: 10.1007/s11910-006-
0015-x
65. Lalli S, Albanese A. The diagnostic challenge of primary dystonia:
evidence from misdiagnosis. Mov Dis. (2010) 25:1619–26. doi: 10.1002/mds.
23137
Frontiers in Neurology | www.frontiersin.org 21 February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
66. Stahl CM, Frucht SJ. Focal task specific dystonia: a review and update. J
Neurol. (2017) 264:1536–41. doi: 10.1007/s00415-016-8373-z
67. Nijenhuis B, Schalkwijk AHP, Hendriks S, Zutt R, Otten E, Tijssen MAJ.
Skater’s cramp: a possible task-specific dystonia in dutch ice skaters. Mov
Disord Clin Pract. (2019) 6:559–66. doi: 10.1002/mdc3.12799
68. Jinnah HA, Albanese A, Bhatia KP, Cardoso F, Da Prat G, de Koning TJ, et al.
Treatable inherited rare movement disorders. Mov Disord. (2018) 33:21–35.
doi: 10.1002/mds.27140
69. Sweney MT, Newcomb TM, Swoboda KJ. The expanding spectrum
of neurological phenotypes in children with ATP1A3 mutations,
alternating hemiplegia of childhood, rapid-onset dystonia-
parkinsonism, CAPOS and beyond. Pediatr Neurol. (2015) 52:56–64.
doi: 10.1016/j.pediatrneurol.2014.09.015
70. Berlot R, Bhatia KP, Kojovi´
c M. Pseudodystonia: a new perspective
on an old phenomenon. Parkinsonism Relat Disord. (2019) 62:44–50.
doi: 10.1016/j.parkreldis.2019.02.008
71. Wissel BD, Dwivedi AK, Merola A, Chin D, Jacob C, Duker AP, et al.
Functional neurological disorders in Parkinson disease. J Neurol Neurosurg
Psychiatry. (2018) 89:566–71. doi: 10.1136/jnnp-2017-317378
72. Kutlubaev MA, Xu Y, Hackett ML, Stone J. Dual diagnosis of epilepsy
and psychogenic nonepileptic seizures: systematic review and meta-analysis
of frequency, correlates, and outcomes. Epilepsy Behav. (2018) 89:70–8.
doi: 10.1016/j.yebeh.2018.10.010
73. Stephen CD, Fung V, Lungu C, Espay AJ. Assessment of emergency
department and inpatient use and costs in adult and pediatric
functional neurological disorders. JAMA Neurol. (2020) e203753.
doi: 10.1001/jamaneurol.2020.3753
74. Bramstedt KA, Ford PJ. Protecting human subjects in neurosurgical trials:
the challenge of psychogenic dystonia. Contemp Clin Trials. (2006) 27:161–4.
doi: 10.1016/j.cct.2005.11.005
75. Shill H, Gerber P. Evaluation of clinical diagnostic criteria for psychogenic
movement disorders. Mov Disord. (2006) 21:1163–8. doi: 10.1002/mds.20921
76. Factor SA, Podskalny GD, Molho ES. Psychogenic movement disorders:
frequency, clinical profile, and characteristics. J Neurol Neurosurg Psychiatry.
(1995) 59:406–12. doi: 10.1136/jnnp.59.4.406
77. Crimlisk HL, Bhatia K, Cope H, David A, Marsden CD, Ron MA. Slater
revisited: 6 year follow up study of patients with medically unexplained
motor symptoms. BMJ. (1998) 316:582–6. doi: 10.1136/bmj.316.7131.582
78. Stone J, Carson A. Functional neurologic symptoms: assessment and
management. Neurol Clin. (2011) 29:1–18. doi: 10.1016/j.ncl.2010.10.011
79. Gelauff J, Stone J, Edwards M, Carson A. The prognosis of functional
(psychogenic) motor symptoms: a systematic review. J Neurol Neurosurg
Psychiatry. (2014) 85:220–6. doi: 10.1136/jnnp-2013-305321
80. Bhatia KP, Bhatt MH, Marsden CD. The causalgia-dystonia syndrome. Brain.
(1993) 116(Pt 4):843–51. doi: 10.1093/brain/116.4.843
81. Ganos C, Edwards MJ, Bhatia KP. Posttraumatic functional
movement disorders. Handb Clin Neurol. (2016) 139:499–507.
doi: 10.1016/B978-0-12-801772-2.00041-2
82. Mainka T, Erro R, Rothwell J, Kühn AA, Bhatia KP, Ganos
C. Remission in dystonia - systematic review of the literature
and meta-analysis. Parkinsonism Relat Disord. (2019) 66:9–15.
doi: 10.1016/j.parkreldis.2019.02.020
83. Hallett M. Functional (psychogenic) movement disorders - clinical
presentations. Parkinsonism Relat Disord. (2016) 22(Suppl. 1):S149–52.
doi: 10.1016/j.parkreldis.2015.08.036
84. Pastore A, Pierri G, Fabio G, Ferramosca S, Gigante A, Superbo M, et al.
Differences in psychopathology and behavioral characteristics of patients
affected by conversion motor disorder and organic dystonia. Neuropsychiatr
Dis Treat. (2018) 14:1287–95. doi: 10.2147/NDT.S151695
85. Ekanayake V, Kranick S, LaFaver K, Naz A, Frank Webb A, LaFrance WC
Jr, et al. Personality traits in psychogenic nonepileptic seizures (PNES) and
psychogenic movement disorder (PMD): neuroticism and perfectionism. J
Psychosom Res. (2017) 97:23–9. doi: 10.1016/j.jpsychores.2017.03.018
86. Williams B, Ospina JP, Jalilianhasanpour R, Fricchione GL, Perez DL. Fearful
attachment linked to childhood abuse, alexithymia, and depression in motor
functional neurological disorders. J Neuropsychiatry Clin Neurosci. (2019)
31:65–9. doi: 10.1176/appi.neuropsych.18040095
87. Perez DL, Young SS, King JN, Guarino AJ, Dworetzky BA, Flaherty A,
et al. Preliminary predictors of initial attendance, symptom burden, and
motor subtype in a US functional neurological disorders clinic population.
Cogn Behav Neurol. (2016) 29:197–205. doi: 10.1097/WNN.00000000000
00106
88. Lang A. Psychogenic dystonia: a review of 18 cases. Can J Neurol Sci. (1995)
22:136–43. doi: 10.1017/S031716710004021X
89. Morgante F, Matinella A, Andrenelli E, Ricciardi L, Allegra C, Terranova
C, et al. Pain processing in functional and idiopathic dystonia: an
exploratory study. Mov Disord. (2018) 33:1340–8. doi: 10.1002/mds.
27402
90. Novaretti N, Cunha ALN, Bezerra TC, Pena Pereira MA, de Oliveira DS,
Macruz Brito, et al. The prevalence and correlation of non-motor symptoms
in adult patients with idiopathic focal or segmental dystonia. Tremor Other
Hyperkinet Mov. (2019) 9:596. doi: 10.5334/tohm.466
91. van den Dool J, Tijssen MA, Koelman JH, Engelbert RH, Visser B.
Determinants of disability in cervical dystonia. Parkinsonism Relat Disord.
(2016) 32:48–53. doi: 10.1016/j.parkreldis.2016.08.014
92. Popkirov S, Hoeritzauer I, Colvin L, Carson AJ, Stone J. Complex
regional pain syndrome and functional neurological disorders – time
for reconciliation. J Neurol Neurosurg Psychiatry. (2019) 90:608–14.
doi: 10.1136/jnnp-2018-318298
93. Schott J. Induction of involuntary movements by peripheral
trauma: an analogy with causalgia. Lancet. (1986) 2:712–6.
doi: 10.1016/S0140-6736(86)90231-X
94. Frei KP, Pathak M, Jenkins S, Truong DD. Natural history of posttraumatic
cervical dystonia. Mov Disord. (2004) 19:1492–8. doi: 10.1002/mds.20239
95. Morgante F, Naro A, Terranova C, Russo M, Rizzo V, Risitano
G, et al. Normal sensorimotor plasticity in complex regional pain
syndrome with fixed posture of the hand. Mov Disord. (2017) 32:149–57.
doi: 10.1002/mds.26836
96. Ranford J, MacLean J, Alluri PR, Comeau O, Godena E, Curt LaFrance W
Jr, et al. Sensory processing difficulties in functional neurological disorder:
a possible predisposing vulnerability? Psychosomatics. (2020) 61:343–52.
doi: 10.1016/j.psym.2020.02.003
97. Bodde MI, Dijkstra PU, den Dunnen WF, Geertzen JH. Therapy-resistant
complex regional pain syndrome type I: to amputate or not? J Bone Joint
Surg Am. (2011) 93:1799–805. doi: 10.2106/JBJS.J.01329
98. Edwards MJ, Alonso-Canovas A, Schrag A, Bloem BR, Thompson PD, Bhatia
K. Limb amputations in fixed dystonia: a form of body integrity identity
disorder? Mov Disord. (2011) 26:1410–4. doi: 10.1002/mds.23671
99. Schrag A, Trimble M, Quinn N, Bhatia K. The syndrome of fixed
dystonia: an evaluation of 103 patients. Brain. (2004) 127(Pt 10):2360–72.
doi: 10.1093/brain/awh262
100. Thomas M, Jankovic J. Psychogenic movement disorders:
diagnosis and management. CNS Drugs. (2004) 18:437–52.
doi: 10.2165/00023210-200418070-00003
101. Espay AJ, Lang AE. The psychogenic toe signs. Neurology. (2011) 77:508–9.
doi: 10.1212/WNL.0b013e318227e4c0
102. Park JE, Maurer CW, Hallett M. The “Whack-a-Mole” sign in
functional movement disorders. Mov Disord Clin Pract. (2015) 2:286–8.
doi: 10.1002/mdc3.12177
103. Fasano A, Valadas A, Bhatia KP, Prashanth LK, Lang AE, Munhoz RP,
et al. Psychogenic facial movement disorders: clinical features and associated
conditions. Mov Disord. (2012) 27:1544–51. doi: 10.1002/mds.25190
104. Tan EK, Jankovic J. Psychogenic hemifacial spasm. J Neuropsychiatry Clin
Neurosci. (2001) 13:380–4. doi: 10.1176/jnp.13.3.380
105. Britton D, Alty JE, Mannion CJ. Oromandibular dystonia: a
diagnosis not to miss. Br J Oral Maxillofac Surg. (2020) 58:520–4.
doi: 10.1016/j.bjoms.2020.02.018
106. Leonard R, Kendall K. Differentiation of spasmodic and psychogenic
dysphonias with phonoscopic evaluation. Laryngoscope. (1999) 109(2 Pt
1):295–300. doi: 10.1097/00005537-199902000-00022
107. Baker J. Functional voice disorders: Clinical presentations
and differential diagnosis. Handb Clin Neurol.
(2016) 139:389–405. doi: 10.1016/B978-0-12-801772-2.
00034-5
Frontiers in Neurology | www.frontiersin.org 22 February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
108. Drane DL, Fani N, Hallett M, Khalsa SS, Perez DL, Roberts NA. A framework
for understanding the pathophysiology of functional neurological disorder.
CNS Spectrums. (2020) 1–7. doi: 10.1017/S1092852920001789
109. Ranawaya R, Riley D, Lang A. Psychogenic dyskinesias in patients
with organic movement disorders. Mov Disord. (1990) 5:127–33.
doi: 10.1002/mds.870050206
110. Lang AE, Voon V. Psychogenic movement disorders: past developments,
current status, and future directions. Mov Disord. (2011) 27:1175–86.
doi: 10.1002/mds.23571
111. Baizabal-Carvallo JF, Jankovic J. Autoimmune and paraneoplastic
movement disorders: an update. J Neurol Sci. (2018) 385:175–84.
doi: 10.1016/j.jns.2017.12.035
112. Mezzaroba L, Alfieri DF, Colado Simão AN, Vissoci Reiche EM. The
role of zinc, copper, manganese and iron in neurodegenerative diseases.
Neurotoxicology. (2019) 74:230–41. doi: 10.1016/j.neuro.2019.07.007
113. Christensen CK, Walsh L. Movement disorders and neurometabolic diseases.
Semin Pediatr Neurol. (2018) 25:82–91. doi: 10.1016/j.spen.2018.02.003
114. Ebrahimi-Fakhari D, Van Karnebeek C, Münchau A. Movement disorders
in treatable inborn errors of metabolism. Mov Disord. (2019) 34:598–613.
doi: 10.1002/mds.27568
115. Munhoz RP, Lang AE. Gestes antagonistes in psychogenic dystonia. Mov
Disord. (2004) 19:331–2. doi: 10.1002/mds.10628
116. Kobylecki C, Kellett MW, Dick JP, Marshall AG. “Reverse
Hoover’s sign” demonstrated by neurophysiology in a patient with
functional dystonia. Parkinsonism Relat Disord. (2016) 29:125–6.
doi: 10.1016/j.parkreldis.2016.05.005
117. Stone J. Functional symptoms in neurology. Pract Neurol. (2009) 9:179–89.
doi: 10.1136/jnnp.2009.177204
118. Tolosa E, Compta Y. Dystonia in Parkinson’s disease. J Neurol. (2006)
253(Suppl. 7):VII7–13. doi: 10.1007/s00415-006-7003-6
119. Stone J, Gelauff J, Carson A. A “twist in the tale”: altered perception
of ankle position in psychogenic dystonia. Mov Disord. (2012) 27:585–6.
doi: 10.1002/mds.24069
120. Stamelou M, Saifee TA, Edwards MJ, Bhatia KP. Psychogenic palatal tremor
may be underrecognized: reappraisal of a large series of cases. Mov Disord.
(2012) 27:1164–8. doi: 10.1002/mds.24948
121. Dreissen YEM, Dijk JM, Gelauff JM, Zoons E, van Poppelen D, Contarino
MF, et al. Botulinum neurotoxin treatment in jerky and tremulous functional
movement disorders: a double-blind, randomised placebo-controlled trial
with an open-label extension. J Neurol Neurosurg Psychiatry. (2019) 90:1244–
50. doi: 10.1136/jnnp-2018-320071
122. Ziegler JS, von Stauffenberg M, Vlaho S, Böhles H, Kieslich M.
Dystonia with secondary contractures: a psychogenic movement disorder
mimicking its neurological counterpart. J Child Neurol. (2008) 23:1316–8.
doi: 10.1177/0883073808318060
123. Edwards MJ, Bhatia KP, Cordivari C. Immediate response to botulinum
toxin injections in patients with fixed dystonia. Mov Disord. (2011) 26:917–8.
doi: 10.1002/mds.23562
124. Stamey W, Jankovic J. The other Babinski sign in hemifacial spasm.
Neurology. (2007) 69:402–4. doi: 10.1212/01.wnl.0000266389.52843.3b
125. Gazulla J, García-Rubio S, Ruiz-Gazulla C, Modrego P. Clinical
categorization of psychogenic blepharospasm. Parkinsonism Relat Disord.
(2015) 21:325–6. doi: 10.1016/j.parkreldis.2014.12.005
126. Fasano A, Tinazzi M. Functional facial and tongue
movement disorders. Handb Clin Neurol. (2016) 139:353–65.
doi: 10.1016/B978-0-12-801772-2.00031-X
127. Tarsy D. Comparison of acute- and delayed-onset posttraumatic cervical
dystonia. Mov Disord. (1998) 13:481–5. doi: 10.1002/mds.870130318
128. Gonzalez-Alegre P, Schneider RL, Hoffman H. Clinical, etiological,
and therapeutic features of jaw-opening and jaw-closing oromandibular
dystonias: a decade of experience at a single treatment center. Tremor Other
Hyperkinet Mov (N Y). (2014) 4:231. doi: 10.5334/tohm.194
129. Hassell TJW, Charles D. Treatment of blepharospasm and
oromandibular dystonia with botulinum toxins. Toxins. (2020) 12:269.
doi: 10.3390/toxins12040269
130. Defazio G, Albanese A, Pellicciari R, Scaglione CL, Esposito M, Morgante F,
et al. Expert recommendations for diagnosing cervical, oromandibular, and
limb dystonia. Neurol Sci. (2019) 40:89–95. doi: 10.1007/s10072-018-3586-9
131. Thompson PD, Obeso JA, Delgado G, Gallego J, Marsden CD. Focal
dystonia of the jaw and the differential diagnosis of unilateral jaw
and masticatory spasm. J Neurol Neurosurg Psychiatry. (1986) 49:651–6.
doi: 10.1136/jnnp.49.6.651
132. Keane J. Wrong-way deviation of the tongue with hysterical hemiparesis.
Neurology. (1986) 36:1406–7. doi: 10.1212/WNL.36.10.1406
133. Kern DS, Lang AE. Successful treatment of functional palatal tremor:
insights into pathogenesis and management. Mov Disord. (2015) 30:875–6.
doi: 10.1002/mds.26226
134. Blitzer A, Brin MF, Simonyan K, Ozelius LJ, Frucht SJ. Phenomenology,
genetics, and CNS network abnormalities in laryngeal dystonia: a 30-year
experience. Laryngoscope. (2018) 128(Suppl. 1):S1–9. doi: 10.1002/lary.27003
135. Chitkara A, Meyer TK, Keidar A, Blitzer A. Singer’s dystonia: first report
of a variant of spasmodic dysphonia. Ann Otol Rhinol Laryngol. (2006)
115:89–92. doi: 10.1177/000348940611500201
136. Koufman JA, Blalock PD. Classification and approach to patients with
functional voice disorders. Ann Otol Rhinol Laryngol. (1982) 91:372.7.
doi: 10.1177/000348948209100409
137. Sa DS, Mailis-Gagnon A, Nicholson K, Lang AE. Posttraumatic painful
torticollis. Mov Disord. (2003) 18:1482–91. doi: 10.1002/mds.10594
138. Raj MS, Schwab JH. An unusual cause of cervical kyphosis. Spine J. (2017)
17:e7–9. doi: 10.1016/j.spinee.2016.09.008
139. Silver MR, Hanfelt J, Factor SA. The “shirt collar sign” of cervical dystonia.
Int J Neurosci. (2017) 127:466–8. doi: 10.1080/00207454.2016.1188815
140. Volkmann J, Mueller J, Deuschl G, Kühn AA, Krauss JK, Poewe W, et al.
Pallidal neurostimulation in patients with medication-refractory cervical
dystonia: a randomised, sham-controlled trial. Lancet Neurol. (2014) 13:875–
84. doi: 10.1016/S1474-4422(14)70143-7
141. Bruno MK, Hallett M, Gwinn-Hardy K, Sorensen B, Considine E,
Tucker S, et al. Clinical evaluation of idiopathic paroxysmal kinesigenic
dyskinesia: new diagnostic criteria. Neurology. (2004) 63:2280–7.
doi: 10.1212/01.WNL.0000147298.05983.50
142. Bruno MK, Lee HY, Auburger GW, Friedman A, Nielsen JE, Lang
AE, et al. Genotype-phenotype correlation of paroxysmal nonkinesigenic
dyskinesia. Neurology. (2007) 68:1782–9. doi: 10.1212/01.wnl.0000262029.
91552.e0
143. Verrotti A, D’Egidio C, Agostinelli S, Gobbi G. Glut1 deficiency: when
to suspect and how to diagnose? Eur J Pediatr Neurol. (2012) 16:3–9.
doi: 10.1016/j.ejpn.2011.09.005
144. Thenganatt MA, Jankovic J. Psychogenic movement disorders. Neurol Clin.
(2015) 33:205–24. doi: 10.1016/j.ncl.2014.09.013
145. Harris S. Psychogenic movement disorders in children and adolescents: an
update. Eur J Pediatr. (2019) 178:581–5. doi: 10.1007/s00431-019-03317-8
146. Canavese C, Ciano C, Zibordi F, Zorzi G, Cavallera V, Nardocci N.
Phenomenology of psychogenic movement disorders in children. Mov
Disord. (2012) 28:1153–7. doi: 10.1002/mds.24947
147. Ferrara J, Jankovic J. Psychogenic movement disorders in children. Mov
Disord. (2008) 23:1875–81. doi: 10.1002/mds.22220
148. Schwingenschuh P, Pont-Sunyer C, Surtees R, Edwards MJ, Bhatia
KP. Psychogenic movement disorders in children: a report of 15
cases and a review of the literature. Mov Disord. (2008) 23:1882–8.
doi: 10.1002/mds.22280
149. Kozlowska K. Functional somatic symptoms in childhood
and adolescence. Curr Opin Psychiatry. (2013) 26:485–92.
doi: 10.1097/YCO.0b013e3283642ca0
150. Ahmed MA, Martinez A, Yee A, Cahill D, Besag FM. Psychogenic and
organic movement disorders in children. Dev Med Child Neurol. (2008)
50:300–4. doi: 10.1111/j.1469-8749.2008.02043.x
151. Kozlowska K, Nunn KP, Rose D, Morris A, Ouvrier RA,
Varghese J. Conversion disorder in Australian pediatric
practice. J Am Acad Child Adolesc Psychiatry. (2007) 46:68–75.
doi: 10.1097/01.chi.0000242235.83140.1f
152. Cassady JD, Kirschke DL, Jones TF, Craig AS, Bermudez OB, Schaffner
W. Case series: outbreak of conversion disorder among Amish
adolescent girls. J Am Acad Child Adolesc Psychiatry. (2005) 44:291–7.
doi: 10.1097/00004583-200503000-00014
153. Kozlowska K, Griffiths KR, Foster SL, Linton J, Williams LM, Korgaonkar
MS. Grey matter abnormalities in children and adolescents with function
Frontiers in Neurology | www.frontiersin.org 23 February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
neurological symptom disorder. Neuroimage: Clinical. (2017) 15:306–14.
doi: 10.1016/j.nicl.2017.04.028
154. Majumdar A, López-Casas J, Poo P, Colomer J, Galvan M, Lingappa L, et al.
Syndrome of fixed dystonia in adolescents–short term outcome in 4 cases.
Eur J Pediatr Neurol. (2009) 13:466–72. doi: 10.1016/j.ejpn.2008.09.005
155. Macerollo A, Batla A, Kassavetis P, Parees I, Bhatia KP, Edwards MJ. Using
reaction time and co-contraction to differentiate acquired (secondary) from
functional ‘fixed’ dystonia. J Neurol Neurosurg Psychiatry. (2015) 86:933–4.
doi: 10.1136/jnnp-2014-309040
156. Schwingenschuh P, Katschnig P, Edwards MJ, Teo JT, Korlipara LV,
Rothwell JC, et al. The blink reflex recovery cycle differs between essential
and presumed psychogenic blepharospasm. Neurology. (2011) 76:610–4.
doi: 10.1212/WNL.0b013e31820c3074
157. Fahn S. The role of anesthesia in the diagnosis and treatment of psychogenic
movement disorders. In: Hallett M, Fahn S, Jankovic J, Lang AE, Cloninger
CR, Yudofsky SC, editors. Psychogenic Movement Disorders: Neurology and
Neuropsychiatry. Philadelphia, PA: Lippincott Williams & Wilkins Publishers
(2006). p. 256–61.
158. Okun MS, Rodriguez RL, Foote KD, Fernandez HH. The “chair test” to aid
in the diagnosis of psychogenic gait disorders. Neurologist. (2007) 13:87–91.
doi: 10.1097/01.nrl.0000256358.52613.cc
159. Espay AJ, Morgante F, Purzner J, Gunraj CA, Lang AE, Chen R. Cortical and
spinal abnormalities in psychogenic dystonia. Ann Neurol. (2006) 59:825–34.
doi: 10.1002/ana.20837
160. Quartarone A, Rizzo V, Terranova C, Morgante F, Schneider S, Ibrahim N,
et al. Abnormal sensorimotor plasticity in organic but not in psychogenic
dystonia. Brain. (2009) 132(Pt 10):2871–7. doi: 10.1093/brain/awp213
161. Avanzino L, Martino D, van de WarrenburgBP, Schneider SA, Abbruzzese G,
Defazio G, et al. Cortical excitability is abnormal in patients with the “fixed
dystonia” syndrome. Mov Disord. (2008) 23:646–52. doi: 10.1002/mds.21801
162. Kobayashi K, Lang AE, Hallett M, Lenz FA. Thalamic neuronal and EMG
activity in psychogenic dystonia compared with organic dystonia. Mov
Disord. (2011) 26:1348–52. doi: 10.1002/mds.23565
163. Ramos VF, Pillai AS, Lungu C, Ostrem J, Starr P, Hallett M. Intraoperative
neurophysiology in deep brain surgery for psychogenic dystonia. Ann Clin
Transl Neurol. (2015) 2:707–10. doi: 10.1002/acn3.206
164. Schwingenschuh P, Katschnig P, Seiler S, Saifee TA, Aguirregomozcorta
M, Cordivari C, et al. Moving toward “laboratory-supported”
criteria for psychogenic tremor. Mov Disord. (2011) 26:2509–15.
doi: 10.1002/mds.23922
165. Fung VS, Jinnah HA, Bhatia K, Vidailhet M. Assessment of patients with
isolated or combined dystonia: an update on dystonia syndromes. Mov
Disord. (2013) 28:889–98. doi: 10.1002/mds.25549
166. Schrag AE, Mehta AR, Bhatia KP, Brown RJ, Frackowiak RS, Trimble MR,
et al. The functional neuroimaging correlates of psychogenic versus organic
dystonia. Brain. (2013) 136(Pt 3):770–81. doi: 10.1093/brain/awt008
167. Maurer CW, LaFaver K, Ameli R, Epstein SA, Hallett M, Horovitz SG.
Impaired self-agency in functional movement disorders: a resting-state fMRI
study. Neurology. (2016) 87:564–70. doi: 10.1212/WNL.0000000000002940
168. Voon V, Gallea C, Hattori N, Bruno M, Ekanayake V, Hallett M. The
involuntary nature of conversion disorder. Neurology. (2010) 74:223–8.
doi: 10.1212/WNL.0b013e3181ca00e9
169. Pick S, Goldstein LH, Perez DL, Nicholson TR. Emotional processing
in functional neurological disorder: a review, biopsychosocial model
and research agenda. J Neurol Neurosurg Psychiatry. (2019) 90:704–11.
doi: 10.1136/jnnp-2018-319201
170. Voon V, Brezing C, Gallea C, Ameli R, Roelofs K, LaFrance WC Jr, et al.
Emotional stimuli and motor conversion disorder. Brain. (2010) 133(Pt
5):1526–36. doi: 10.1093/brain/awq054
171. Blakemore RL, Sinanaj I, Galli S, Aybek S, Vuilleumier P.
Aversive stimuli exacerbate defensive motor behaviour in motor
conversion disorder. Neuropsychologia. (2016) 93(Pt A):229–41.
doi: 10.1016/j.neuropsychologia.2016.11.005
172. Espay AJ, Maloney T, Vannest J, Norris MM, Eliassen JC, Neefus E,
et al. Dysfunction in emotion processing underlies functional (psychogenic)
dystonia. Mov Disord. (2018) 33:136–45. doi: 10.1002/mds.27217
173. Canu E, Agosta F, Tomic A, Sarasso E, Petrovic I, Piramide N,
et al. Breakdown of the affective-cognitive network in functional
dystonia. Hum Brain Mapp. (2020) 41:3059–76. doi: 10.1002/hbm.
24997
174. Tomic A, Agosta F, Sarasso E, Petrovic I, Basaia S, Pesic D, et al. Are there two
different forms of functional dystonia? A multimodal brain structural MRI
study. Mol Psychiatry. (2018) 25:3350–9. doi: 10.1038/s41380-018-0222-2
175. Maurer CW, LaFaver K, Limachia GS, Capitan G, Ameli R, Sinclair S, et al.
Gray matter differences in patients with functional movement disorders.
Neurology. (2018) 91:e1870–9. doi: 10.1212/WNL.0000000000006514
176. Bègue I, Adams C, Stone J, Perez DL. Structural alterations in
functional neurological disorder and related conditions: a software
and hardware problem? Neuroimage Clin. (2019) 22:101798.
doi: 10.1016/j.nicl.2019.101798
177. Molloy FM, Carr TD, Zeuner KE, Dambrosia JM, Hallett M. Abnormalities of
spatial discrimination in focal and generalized dystonia. Brain. (2003) 126(Pt
10):2175–82. doi: 10.1093/brain/awg219
178. Katschnig P, Edwards MJ, Schwingenschuh P, Aguirregomozcorta M,
Kägi G, Rothwell JC, et al. Mental rotation of body parts and sensory
temporal discrimination in fixed dystonia. Mov Disord. (2010) 25:1061–7.
doi: 10.1002/mds.23047
179. Stone KD, Dijkerman HC, Bekrater-Bodmann R, Keizer A. Mental rotation
of feet in individuals with Body Integrity Identity Disorder, lower-limb
amputees, and normally-limbed controls. PLoS ONE. (2019) 14:e0221105.
doi: 10.1371/journal.pone.0221105
180. Morgante F, Tinazzi M, Squintani G, Martino D, Defazio G, Romito
L, et al. Abnormal tactile temporal discrimination in psychogenic
dystonia. Neurology. (2011) 77:1191–7. doi: 10.1212/WNL.0b013e3182
2f0449
181. Stone J. Functional neurological disorders: the neurological
assessment as treatment. Pract Neurol. (2016) 16:7–17.
doi: 10.1136/practneurol-2015-001241
182. Carson A, Lehn A, Ludwig L, Stone J. Explaining functional disorders
in the neurology clinic: a photo story. Pract Neurol. (2016) 16:56–61.
doi: 10.1136/practneurol-2015-001242
183. Gelauff J, Dreissen YEM, Tijssen MA, Stone J. Treatment of
functional motor disorders. Curr Treat Options Neurol. (2014) 16:286.
doi: 10.1007/s11940-014-0286-5
184. Nielsen G, Stone J, Matthews A, Brown M, Sparkes C, Farmer R,
et al. Physiotherapy for functional motor disorders: a consensus
recommendation. J Neurol Neurosurg Psychiatry. (2015) 86:1113–9.
doi: 10.1136/jnnp-2014-309255
185. Nielsen G, Stone J, Edwards MJ. Physiotherapy for functional
(psychogenic) motor symptoms: a systematic review. J
Psychosom Res. (2013) 75:93–102. doi: 10.1016/j.jpsychores.2013.
05.006
186. Edwards MJ, Stone J, Lang AE. Functional/psychogenic movement
disorders: do we know what they are? Mov Disord. (2014) 29:1696–7.
doi: 10.1002/mds.26039
187. Barnett C, Davis R, Mitchell C, Tyson S. The vicious cycle of functional
neurological disorders: a synthesis of healthcare professionals’ views
on working with patients with functional neurological disorder.
Disabil Rehabil. (2020) 1822935. doi: 10.1080/09638288.2020.
1822935
188. Edwards MJ, Stone J, Nielsen G. Physiotherapists and patients with
functional (psychogenic) motor symptoms: a survey of attitudes
and interest. J Neurol Neurosurg Psychiatry. (2012) 83:655–8.
doi: 10.1136/jnnp-2011-302147
189. Dallocchio C, Arbasino C, Klersy C, Marchioni E. The effects of physical
activity on psychogenic movement disorders. Mov Disord. (2010) 25:421–5.
doi: 10.1002/mds.22952
190. Trieschmann RB, Stolov WC, Montgomery ED. An approach to the
treatment of abnormal ambulation resulting from conversion reaction. Arch
Phys Med Rehabil. (1970) 51:198–206.
191. Ness D. Physical therapy management for conversion
disorder: case series. J Neurol Phys Ther. (2007) 31:30–9.
doi: 10.1097/01.NPT.0000260571.77487.14
192. Speed J. Behavioral management of conversion disorder:
retrospective study. Arch Phys Med Rehabil. (1996) 77:147–54.
doi: 10.1016/S0003-9993(96)90159-8
Frontiers in Neurology | www.frontiersin.org 24 February 2021 | Volume 11 | Article 605262

Frucht et al. Functional Dystonia: Diagnosis and Treatment
193. Jordbru AA, Smedstad LM, Klungsøyr O, Martinsen EW. Psychogenic gait
disorder: a randomized controlled trial of physical rehabilitation with one-
year follow-up. J Rehabil Med. (2014) 46:181–7. doi: 10.2340/16501977-1246
194. Nielsen G, Ricciardi L, Demartini B, Hunter R, Joyce E, Edwards
MJ. Outcomes of a 5-day physiotherapy programme for functional
(psychogenic) motor disorders. J Neurol. (2015) 262:674–81.
doi: 10.1007/s00415-014-7631-1
195. Maggio JB, Ospina JP, Callahan J, Hunt AL, Stephen CD, Perez
DL. Outpatient physical therapy for functional neurological
disorder: a preliminary feasibility and naturalistic outcome study
in a U.S. cohort. J Neuropsychiatry Clin Neurosci. (2020) 32:85–9.
doi: 10.1176/appi.neuropsych.19030068
196. Jacob AE, Kaelin DL, Roach AR, Ziegler CH, LaFaver K. Motor
retraining (MoRe) for functional movement disorders: outcomes from a 1-
week multidisciplinary rehabilitation program. PM R. (2018) 10:1164–72.
doi: 10.1016/j.pmrj.2018.05.011
197. Wulf G, Lewthwaite R. Optimizing performance through intrinsic
motivation and attention for learning: the OPTIMAL theory of
motor learning. Psychon Bull Rev Actions. (2016) 23:1382–414.
doi: 10.3758/s13423-015-0999-9
198. Demartini B, Batla A, Petrochilos P, Fisher L. Edwards M,
Joyce E. Multidisciplinary treatment for functional neurological
symptoms: a prospective study. J Neurol. (2014) 261:2370–7.
doi: 10.1007/s00415-014-7495-4
199. Nicholson C, Edwards MJ, Carson AJ, Gardiner P, Golder D, Hayward
K, et al. Occupational therapy consensus recommendations for functional
neurological disorder. J Neurol Neurosurg Psychiatry. (2020) 91:1037–45.
doi: 10.1136/jnnp-2019-322281
200. Zeuner K, Molloy FM. Abnormal reorganization in focal hand dystonia
- sensory and motor training programs to retrain cortical function.
Neurorehabilitation. (2008) 23:43–53. doi: 10.3233/NRE-2008-23105
201. Butler K, Sadnicka A, Freeman J, Meppelink AM, Parees I, Marsden
J, et al. Sensory-motor rehabilitation therapy for task-specific focal
hand dystonia: a feasibility study. Hand Ther. (2018) 23:53–63.
doi: 10.1177/1758998318764219
202. Ranford J, MacLean J, Perez DL. Additional occupational therapy
considerations for functional neurological disorders: a potential
role for sensory processing. CNS Spectrums. (2018) 23:194–5.
doi: 10.1017/S1092852918000950
203. Champagne T. The influence of posttraumatic stress disorder, depressing and
sensory processing patterns on occupational engagement: a case study. Work.
(2011) 38:67–75. doi: 10.3233/WOR-2011-1105
204. Pfiefer B, Kinnealey M. Treatment of sensory defensiveness in adults. Occup
Ther Int. (2003) 10:175–84. doi: 10.1002/oti.184
205. Barnett C, Armes J, Smith C. Speech, language and swallowing impairments
in functional neurological disorder: a scoping review. Int J Lang Commun
Disord. (2019) 54:309–20. doi: 10.1111/1460-6984.12448
206. Ricciardi L, Edwards MJ. Treatment of functional (psychogenic)
movement disorders. Neurotherapeutics. (2014) 11:201–7.
doi: 10.1007/s13311-013-0246-x
207. Espay AJ, Ries S, Maloney T, Vannest J, Neefus E, Dwivedi AK, et al.
Clinical and neural responses to cognitive behavioral therapy for functional
tremor. Neurology. (2019) 93:e1787–98. doi: 10.1212/WNL.00000000000
08442
208. Sharpe M, Walker J, Williams C, Stone J, Cavanagh J, Murray G,
et al. Guided self-help for functional (psychogenic) symptoms: a
randomized controlled efficacy trial. Neurology. (2011) 77:564–72.
doi: 10.1212/WNL.0b013e318228c0c7
209. Voon V, Lang AE. Antidepressant treatment outcomes of
psychogenic movement disorder. J Clin Psychiatry. (2005) 66:1529–34.
doi: 10.4088/JCP.v66n1206
210. Williams DT, Lafaver K, Carson A, Fahn S. Inpatient treatment for
functional neurologic disorders. Handb Clin Neurol. (2016) 139:631–41.
doi: 10.1016/B978-0-12-801772-2.00051-5
211. Ibrahim NM, Martino D, van de Warrenburg BPC, Quinn NP,
Bhatia KP, Brown RJ, et al. The prognosis of fixed dystonia:
a follow-up study. Parkinsonism Relat Disord. (2009) 15:592–7.
doi: 10.1016/j.parkreldis.2009.02.010
212. Termsarasab P, Thammongkolchai T, Frucht SJ. Medical treatment of
dystonia. J Clin Mov Disord. (2016) 3:19. doi: 10.1186/s40734-016-
0047-6
213. Aum DJ, Tierney TS. Deep brain stimulation: foundations and future trends.
Front Biosci. (2018) 23:162–82. doi: 10.2741/4586
214. Thomas M, Vuong KD, Jankovic J. Long-term prognosis of patients with
psychogenic movement disorders. Parkinsonism RelatD isord. (2006) 12:382–
7. doi: 10.1016/j.parkreldis.2006.03.005
215. Pick S, Anderson DG, Asadi-Pooya AA, Aybek S, Baslet G, Bloem BR, et al.
Outcome measurement in functional neurological disorder: a systematic
review and recommendations. J Neurol Neurosurg Psychiatry. (2020) 91:638–
49. doi: 10.1136/jnnp-2019-322180
Conflict of Interest: DP has received honoraria for continuing medical education
lectures in functional neurological disorder.NS received financial support from
John Wiley & Sons for serving as editor in chief to Brain & Behavior. CS has
provided scientific advisory for Xenon Pharmaceuticals and SwanBio Pharma and
received research funding from Sanofi-Genzyme for a study of video oculography
in late-onset GM2 gangliosidosis. He has received financial support from Sanofi-
Genzyme, Biogen and Biohaven for the conduct of clinical trials.
The remaining author declares that the research was conducted in the absence of
any commercial or financial relationships that could be construed as a potential
conflict of interest.
Copyright © 2021 Frucht, Perez, Callahan, MacLean, Song, Sharma and Stephen.
This is an open-access article distributed under the terms of the Creative Commons
Attribution License (CC BY). The use, distribution or reproduction in other forums
is permitted, provided the original author(s) and the copyright owner(s) are credited
and that the original publication in this journal is cited, in accordance with accepted
academic practice. No use, distribution or reproduction is permitted which does not
comply with these terms.
Frontiers in Neurology | www.frontiersin.org 25 February 2021 | Volume 11 | Article 605262