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Cataplexy - Clinical aspects, pathophysiology and management strategy

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Cataplexy is the pathognomonic symptom of narcolepsy, and is the sudden uncontrollable onset of skeletal muscle paralysis or weakness during wakefulness. Cataplexy is incapacitating because it leaves the individual awake but temporarily either fully or partially paralyzed. Occurring spontaneously, cataplexy is typically triggered by strong positive emotions such as laughter and is often underdiagnosed owing to a variable disease course in terms of age of onset, presenting symptoms, triggers, frequency and intensity of attacks. This disorder occurs almost exclusively in patients with depletion of hypothalamic orexin neurons. One pathogenetic mechanism that has been hypothesized for cataplexy is the activation, during wakefulness, of brainstem circuitry that normally induces muscle tone suppression in rapid eye movement sleep. Muscle weakness during cataplexy is caused by decreased excitation of noradrenergic neurons and increased inhibition of skeletal motor neurons by γ-aminobutyric acid-releasing or glycinergic neurons. The amygdala and medial prefrontal cortex contain neural pathways through which positive emotions probably trigger cataplectic attacks. Despite major advances in understanding disease mechanisms in cataplexy, therapeutic management is largely symptomatic, with antidepressants and γ-hydroxybutyrate being the most effective treatments. This Review describes the clinical and pathophysiological aspects of cataplexy, and outlines optimal therapeutic management strategies.
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1
Department of
Neurology, INSERM
U1061, University of
Montpellier,
Montpellier34295,
France (Y.D., R.L.).
Neurobiology Research
151A3, University
College Los Angeles,
Veterans Administration
Greater Los Angeles
Healthcare System,
16111 Plummer Street,
North Hills, CA 91343,
USA (J.M.S.). Centre for
Brain Sciences,
Department of Cell and
Systems Biology,
University of Toronto,
Toronto, ON M4X 1H7,
Canada (Z.A.T., J.H.P.).
Correspondence to: Y.D.
ydauvilliers@yahoo.fr
Cataplexy—clinical aspects, pathophysiology
and management strategy
Yves Dauvilliers, Jerry M. Siegel, Regis Lopez, Zoltan A. Torontali and John H. Peever
Abstract | Cataplexy is the pathognomonic symptom of narcolepsy, and is the sudden uncontrollable onset
of skeletal muscle paralysis or weakness during wakefulness. Cataplexy is incapacitating because it leaves
the individual awake but temporarily either fully or partially paralyzed. Occurring spontaneously, cataplexy is
typically triggered by strong positive emotions such as laughter and is often underdiagnosed owing to a variable
disease course in terms of age of onset, presenting symptoms, triggers, frequency and intensity of attacks. This
disorder occurs almost exclusively in patients with depletion of hypothalamic orexin neurons. One pathogenetic
mechanism that has been hypothesized for cataplexy is the activation, during wakefulness, of brainstem
circuitry that normally induces muscle tone suppression in rapid eye movement sleep. Muscle weakness during
cataplexy is caused by decreased excitation of noradrenergic neurons and increased inhibition of skeletal motor
neurons by γ‑aminobutyric acid‑releasing or glycinergic neurons. The amygdala and medial prefrontal cortex
contain neural pathways through which positive emotions probably trigger cataplectic attacks. Despite major
advances in understanding disease mechanisms in cataplexy, therapeutic management is largely symptomatic,
with antidepressants and γ‑hydroxybutyrate being the most effective treatments. This Review describes the
clinical and pathophysiological aspects of cataplexy, and outlines optimal therapeutic management strategies.
Dauvilliers, Y. etal. Nat. Rev. Neurol. advance online publication 3 June 2014; doi:10.1038/nrneurol.2014.97
Introduction
Cataplexy is defined as sudden involuntary muscle weak-
ness or paralysis during wakefulness, typically triggered
by strong emotions, and is the pathognomonic symptom
of narcolepsy with cataplexy—a sleep disorder that affects
0.06% of the adult population.1,2 In addition to cataplexy,
narcolepsy is characterized by sleep paralysis, sleep-onset
rapid eye movement (REM) periods, hypnagogic hallu-
cinations, and fragmented night-time sleep.3,4 Cataplexy
is virtually exclusive to patients with narcolepsy, and is
the optimal behavioural biomarker of this disease.2–4
Excessive daytime sleepiness (EDS) is usually the present-
ing symptom of narcolepsy, and cata plexy often develops
within 1year of birth and persists for life, although some
patients report a delay between EDS and the onset of cata-
plexy of more than 5years.5 The age of onset of narco-
lepsy ranges from early childhood (with 5% of patients in
the prepubertal stage) to the fifth decade, with a bimodal
distribution that peaks at 15years and 35years of age.5
Patients with narcolepsy have difficulty in executing daily
activities, socializing and maintaining personal relation-
ships mainly due to cataplexy and EDS, and are esti-
mated to experience a quality of life that is comparable or
inferiorto that of patients with epilepsy or sleep apnoea.6,7
Cataplexy has been identified in a range of species,
including humans, horses, dogs and mice.8,9 Genetic
studies of cataplexy in dogs and mice indicate that loss
of functional orexin or mutations in the genes encod-
ing orexin receptors underlie the pathophysiology.10–13
Humans with narcolepsy and cataplexy have a marked
decrease in orexin levels in cerebrospinal fluid (CSF),
together with a decreased number of orexin neurons
in postmortem brain tissue.2,14–16 The close associa-
tions of narcolepsy or cataplexy with HLA-DQB1*06:02,
polymorphisms in the T-cell receptor α and P2RY11
genes, and the pandemic anti-H1N1 vaccination,
suggest that the loss of orexin neurons might have an
autoimmuneorigin.17–23
This Review is timely because cataplexy is still an
under-recognized symptom of narcolepsy—a disease
that is currently underdiagnosed, especially in children.
In Europe, the delay between the onset of symptoms and
a correct diagnosis is about 10years, due to insufficient
awareness and understanding of the condition among
clinicians and individuals.24 Considering that the onset of
narcolepsy is mainly in the second decade of life, and the
condition can remain untreated for a further 10years,
many patients are affected during the most important
period in their education and/or career. To overcome
these consequences of narcolepsy and cataplexy, early
diagnosis and treatment are essential to best improve
patient quality of life.
Features of cataplexy
Cataplexy can be difficult to diagnose, as the symp-
toms vary not only between patients but also within
Competing interests
Y.D. declares that he has received speaker honoraria and
support for travel to meetings and has participated on the
advisory boards for the following companies: UCB Pharma, JAZZ
and Bioprojet. The other authors declare no competing interests.
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individuals. For example, different cataplexy phenotypes
exist in terms of age of onset, presenting symptoms (that
is, the muscles affected), triggers (for example, laughter
versus anger), frequency and severity, and the frequency
of attacks often decreases with time.4,25,26 Cataplectic
attacks range from partial muscle weakness to complete
paralysis, but are always bilateral, even if one side of the
body is more affected than the other. These attacks are
debilitating for patients because they leave the affected
individual awake but either fully or partially para lyzed.
Cataplexy affects all skeletal muscles apart from the dia-
phragm and extraocular muscles, but its greatest effect
is on facial and neck muscles. Typically, the result is
dysarthria, twitching of the facial muscles, jaw tremor,
head dropping or jaw dropping, dropping of objects,
and/or buckling of the knees (Supplementary Video 1
online). Extreme muscle weakness in the knees, arms and
shoulders is also common. 50% of patients with cataplexy
experience both partial muscle weakness and complete
paralysis, whereas 30% experience only partial paraly-
sis.25,27 Injury during cataplexy is uncommon because
most patients ‘feel’ the onset of muscle weakness and
are able to sit or lie down. In rare instances, however, a
cataplectic attack may result in fractures or bruises to the
patient, and might be dangerous in certain settings (for
example, during swimming).
During a cataplectic attack, patients remain con-
scious and are able to remember what happened to them
before, during and after the cataplectic episode.28 Some
patients with narcolepsy report hypnagogic hallucina-
tions during attacks, and some patients enter into REM
sleep, but this is rare.29 Skeletal muscle tone is reduced or
absent during a cataplectic episode. A study of the neuro-
physiology of cataplexy indicates waxing and waning of
postural muscle tone during cataplexy attacks that pro-
gresses along muscle groups rostro-caudally. Most epi-
sodes are accompanied by reduced heart rate and EEG
desynchronization (Figure1).29,30
The duration of an attack varies from several seconds
to several minutes, and in rare instances it lasts for
hours—a condition known as status cataplecticus.2 The
frequency of cataplectic attacks in patients varies from
fewer than one episode per year to several episodes per
day. Many patients with narcolepsy report that sleep loss
and fatigue worsen the frequency of cataplectic attacks,
but studies have not shown a clear link between sleep
patterns (total sleep time, sleep efficiency, percentage of
sleep stages, periodic leg movements and REM behaviour
disorder), EDS and the severity of cataplexy.31 Cataplexy
persists throughout life, although the frequency of
attacks might decrease with age.31 Men often experience
a higher number of cataplectic attacks than do women.31
Near the time of disease onset, children with narco-
lepsy often display abnormal motor behaviour that
does not meet the classic definition of cataplexy.31 Some
children display a complex array of ‘negative’ (that is,
hypotonic) and ‘active’ movements (for example, jaw
opening with tongue protrusion, closure of eyelids and
dyskinetic– dystonic movements) that can occur without
any obvious emotional triggers.32 These symptoms,
however, decrease over a 3year period and evolve into
the classic cataplectic attacks described.33
In clinical practice, cataplexy is mostly diagnosed
on the basis of the patients history. Cataplexy is often
documented in verbal reports, videos taken by the
patient’s family or, in some patients, after cataplec-
tic episodes that occur in the presence of a physician.
The clinical description of cataplectic attacks should be
precise to enable classification as ‘typical’ or ‘clear-cut’,
and should include triggering factors, muscles that are
affected, duration and frequency of attacks. In patients
with a potential differential diagnosis, the term ‘atypical’
cataplexy should be used and an assay of orexin levels
in CSF used to verify the diagnosis of orexin deficiency
ornarcolepsy.
Trigger factors
In the International Classification of Sleep Disorders,
narcolepsy is classified as type1 or type2.34 According
to this classification, type1 narcolepsy (narcolepsy with
cataplexy) is defined as EDS that persists for at least
3months, plus at least two of the following: clear-cut
cataplexy, a positive result on the Multiple Sleep Latency
Test (that is, time elapsed from the start of a daytime nap
period to the first signs of sleep of ≤8 min, and two or
more sleep-onset REM periods) or low levels of orexin
in CSF. Type2 narcolepsy (narcolepsy without cataplexy,
which as an entity remains controversial with unknown
prevalence) is diagnosed as EDS that persists for at least
3months and a positive result on the Multiple Sleep
Latency Test, in the presence of normal levels of orexin.
The presence of atypical cataplexy is sometimes reported
in type2 narcolepsy.
More than 90% of patients with narcolepsy and cata-
plexy present with low levels of orexin (<110 pg/ml) in
CSF, which undoubtedly stem from the loss of approxi-
mately 90% of orexin-expressing neurons.2,14,15 By con-
trast, more than 80% of individuals who are healthy or
have atypical cataplexy have normal levels of orexin.35
Importantly, a postmortem study of a patient who exhib-
ited narcolepsy without cataplexy indicated loss of 33%
of orexin-positive cells, largely in the posterior hypo-
thalamus.36 This finding suggests that narcolepsy with
Key points
Cataplexy is the pathognomonic symptom of narcolepsy, and is characterized
by sudden involuntary loss of skeletal muscle tone during wakefulness, typically
triggered by strong positive emotions
The pathogenesis of cataplexy in human narcolepsy involves degeneration of
orexin neurons in the hypothalamus; genetically induced orexin deficiency causes
cataplexy in both mice and dogs
Cataplexy is thought to result from activation during wakefulness of the sleep
circuitry involved in rapid eye movement sleep
Reduced noradrenergic and increased inhibitory input to motor neurons causes
muscle weakness or paralysis during cataplexy; positive emotions trigger
cataplexy through neuronal pathways in the amygdala and medial prefrontal cortex
■ γ‑Hydroxybutyrate (GHB) and antidepressants are effective treatments for
cataplexy, but most treatments (excluding GHB) are used ‘off‑label’
Novel and experimental treatments to manage cataplexy are required, including
orexin replacement therapy and immune‑based therapies
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cataplexy only ensues when a patient loses almost all
their orexin-positive cells.14,15,36
The association of H1N1 virus infection or anti-H1N1
vaccination with narcolepsy or narcolepsy with cata-
plexy is well-established.21,23,37 For example, a substan-
tial spike in newly diagnosed cases of narcolepsy or
narcolepsy with cataplexy in children and adolescents
who were exposed to the H1N1 virus or the vaccine
has been recorded.21,23,37 A study of patients with narco-
lepsy revealed the presence of CD4+ Tcells that were
reactive to orexin and might also be reactive to a similar
epitope on the H1N1 virus.38 The presence of high titres
a
b
Cataplexy onset
EOGD
EOGG
EMG1
Fp2-O2
Fp1-O1
Fp2-C4
C4-O2
Fp1-C3
C3-O1
Fp2-T4
C4-T4
O2-T4
FP1-T3
C3-T3
O1-T3
ECG
EOGD
EOGG
EMG
Fp2-O2
Fp1-O1
Fp2-C4
C4-O2
Fp1-C3
C3-O1
Fp2-T4
C4-T4
O2-T4
FP1-T3
C3-T3
O1-T3
ECG
Figure 1 | Video‑polysomnographic recording of a patient during a cataplectic attack with loss of muscle tone. Video clips
were taken sequentially over a period of a | 2 min and b | 30 s. The patient presents with sustained loss of muscle tone
thatalternates with brief enhanced EMG activity leading to a flapping up‑and‑down motion of the body segments. These
movements were reported as voluntary by the patient, who was trying to fight against the repetitive postural losses. The
patient was fully conscious during the entire episode. Note that the EEG is characterized by low voltage frequencies
(alphaand theta) and a decrease in heart rate during the brief suppressions of EMG activity. Abbreviations: ECG,
electrocardiogram; EMG, electromyogram; EOGD, right electrooculogram; EOGG, left electrooculogram. Written consent
forpublication was obtained from the patient.
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of antibodies against streptolysin O and Tribbles homo-
logue2 (TRB-2, a protein that is abundant in orexin
neurons) near the onset of narcolepsy also suggests
an auto immune basis for the disease and the potential
for immunotherapy by generating crossreactive anti-
bodies.39,40 However, autoantibodies against TRB-2 in
mice and other species might be a consequence rather
than a cause of orexin neuron damage.
A link between cataplexy and emotion
A cataplectic attack is generally triggered by strong
positive emotions such as excited laughter, repartee
(for example, making a clever remark), elation, or sur-
prise (for example, unexpectedly meeting a friend).25
Infrequently, they are associated with negative emotions
such as frustration or anger or, even more rarely, by stress,
fear or physical effort.2,25,41 Although a certain intensity of
positive emotion is required to trigger a catapletic attack,
nearly half of all patients experience spontaneous attacks
that have no identifiable trigger.25,32,42
Benign muscle weakness, especially in the lower limbs,
often occurs in healthy people when they laugh, hence
the expression ‘weak with laughter’.43 This muscle weak-
ness is linked to suppression of the Hoffmann reflex,
which occurs during normal laughter in healthy indi-
viduals.44 Orexin neurons are active in the response
to strong emotions; therefore, loss of orexin-positive
neurons in patients who have narcolepsy or narcolepsy
with cataplexy hypothetically destabilizes the motor
control system within the brainstem such that posi-
tive emotions trigger severe muscle weakness or total
motorparalysis.8,45
Evidence exists that patients with cataplexy have
altered neuronal responses to positive emotions. For
example, neurophysiological data show that process-
ing of humorous stimuli is temporally disturbed in
patients with narcolepsy or narcolepsy and cataplexy.46
Neuroimaging studies show that patients with narco-
lepsy have a reduced threshold for neuronal activation
in the amygdala (a brain region that has a key role in
the regulation of emotional activity) in response to
both humorous and reward stimuli compared with con-
trols.47,48 In addition, functional neuroimaging studies
describe changes in brain perfusion49 and glucose
metabolism50 during cataplexy in humans. A PET study
revealed increased metabolic activity during cataplexy
in the bilateral precentral and postcentral gyri and
primary somatosensory cortex, and a marked decrease
in activity in the hypothalamus.50 A study using single-
photon emission CT indicated hyperperfusion in the
right amygdala, bilateral cingulate gyri, basal ganglia,
thalamus, premotor cortex, sensorimotor cortex, right
insula, and brainstem, and hypoperfusion in the pre-
frontal cortex and occipital lobe, during cataplexy.49,50
Abnormal functioning of the amygdala during cataplexy
might stem from orexin deficiency, because the release
of orexin from neurons is maximal when healthy indi-
viduals are experiencing positive emotions.51 Animal
studies also indicate that cataplexy is associated with
abnormal function of the amygdala. Postmortem data
show marked axonal degeneration in the amygdala of
narcoleptic dogs, and electrophysiological recordings
demonstrate that individual cells in the amygdala have
increased firing rates during cataplexy.52,53
Animal models
Genetic studies in narcoleptic dogs and mice have pro-
vided valuable insights into the pathophysiology of cata-
plexy. Genetic deletion of Hcrt, which encodes orexin,
in mice and the consequent degeneration of orexin-
expressing neurons induces a behavioural pheno type
that recapitulates the cardinal features of human narco-
lepsy, including cataplexy, sleepiness and disturbed REM
sleep.10,11,13 In dogs, introduction of exon skipping into
the Hcrt-R2 gene causes a narcoleptic phenotype, includ-
ing cataplexy.12,53 These findings not only corroborate
human data showing that narcolepsy or narcolepsy and
cataplexy is the result of abnormal functioning of the
orexin system (Figure2), but also suggest that the orexin
system is important in promoting arousal, controlling
REM sleep, and regulating postural muscle tone.45,53
Cataplectic attacks in Hcrt–/– mice seem remarkably
similar to those in human cataplexy (Table1). Attacks
are characterized by the rapid onset of skeletal muscle
paralysis during wakefulness, resulting in abrupt pos-
tural collapse that terminates purposeful behaviour
(Supplementary Video 2 online).8 Mice seem to be awake
during attacks, because they respond to visual stimuli,
and their EEG activity is similar to the spectrum of
waking EEG activity seen during cataplectic episodes
in children.13,54 Most cataplectic attacks in Hcrt–/– mice
range from 15 s to 2 min, with a mean duration of about
LH
Orexin
Muscle
Amygdala
Excitatory
Disinhibition
Inhibitory
Positive
emotions
mPFC
SubC
vlPAG
LPT LC Cataplexy
MM Motor
neurons
Figure 2 | Hypothetical circuits and pathways controlling cataplexy in the rodent
brain. Activation during wakefulness of neural circuits involved in REM sleep
paralysis is thought to underlie cataplexy, and is probably triggered by a two‑part
brainstem circuit—the SubC and MM connection. Glutamatergic neurons in the
SubC trigger REM paralysis by activating GABAergic or glycinergic cells in the MM,
which in turn project to and inhibit skeletal motor neurons. When a positive
emotion is experienced, GABAergic neurons in the CeA switch on and inhibit cells
in the LC, vlPAG and LPT. The LC–vlPAG–LPT circuit normally prevents muscle
paralysis during wakefulness by suppressing the activity of SubC neurons.
GABAergic CeA neurons inhibit neurons in the LC–vlPAG–LPT circuit, which in turn
disinhibits the SubC to motor neuron circuit, triggering muscle paralysis and
cataplexy. Muscle paralysis in cataplexy is also enabled by loss of noradrenergic
input from LC neurons, which are inhibited during cataplexy. In healthy individuals,
orexin‑expressing neuronal activity cancels out the inhibitory effect of amygdalar
neurons. Abbreviations: CeA, central amygdala; GABA, γ‑aminobutyric acid; LC,
locus coeruleus; LH, lateral hypothalamus; LPT, lateral pontine tegmentum; MM,
medial medulla; mPFC, medial prefrontal cortex; REM, rapid eye movement; SubC,
subcoereulus; vlPAG, ventrolateral periaqueductal grey.
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60 s, similar to human cataplexy. Cataplectic attacks
end with rapid restoration of muscle tone and resump-
tion of normal waking behaviour, as they do in patients
withnarcolepsy.
As in humans with narcolepsy, cataplectic attacks in
narcoleptic dogs and mice can be triggered by posi-
tive emotional stimuli. In narcoleptic dogs, cataplexy is
triggered by palatable foods, play or sex, and in narco-
leptic mice it is triggered by reward stimuli such as
social reunion, running in wheels and palatable food
(Supplementary Video 3 online).55,56 The frequency of
cataplectic attacks is significantly increased when Hcr t–/–
mice are given access to running wheels and chocolate,
which are both reward stimuli for mice.41,57 EEG record-
ings in narcoleptic mice show that cataplexy begins with
a brief phase of wakefulness, followed by high-amplitude
irregular theta activity and then by short 1–2 s bursts of
high-amplitude, regular (~7 Hz), hypersynchronous
paroxysmal theta activity.54 Intracranial EEG recordings
also show that this activity involves the medial pre frontal
cortex, a region associated with reward-driven motor
impulses.54 Interestingly, hypersynchronous paroxysmal
theta activity (~4 Hz) is also observed at the onset of cata-
plexy in children with narcolepsy. These bursts of activity
might represent medial prefrontal cortical activity, but
the clinical relevance of this finding is unclear.54
Neurobiology
A longstanding hypothesis in sleep medicine is that cata-
plexy results from the intrusion of REM sleep paralysis
into wakefulness.2,4,58 This idea stems from the obser-
vation that cataplexy and REM sleep paralysis have a
common neural mechanism.59 For example, tricyclic
antidepressants , which are used to alleviate cataplexy,
also suppress REM sleep, and rapid withdrawal of these
drugs causes a rebound of either cataplexy or REM
sleep.2,60 Deep tendon and monosynaptic Hoffmann
reflex activity are absent during both cataplexy and
REM sleep.2,4,44 Neuroimaging studies of patients with
narcolepsy and electrophysiological recordings from
isolated cells in narcoleptic dogs show that the brain-
stem circuitry involved in REM sleep might have similar
activity during both REM sleep and cataplectic epi-
sodes.49,52 The underlying cause of clinical cataplexy
is a reduction in skeletal motor neuron activity, which
results from increased inhibitory and reduced excitatory
signalling in the brain.41,58 Inhibitory signals are pro-
duced by γ-aminobutyric acid-releasing (GABAergic)
and glycinergic neurons in the medial medulla, which
are intensely activated during cataplexy and REM sleep,
but not during normal waking.55,61,62 Simultaneously,
pontine grey neurons, which are responsible for atonia
both in cataplexy and in REM sleep, activate GABAergic
neurons, which in turn inhibit noradrenergic neurons in
the locus coeruleus (Figure2).63 The cessation of firing
of noradrenergic neurons stops the release of noradrena-
line to motor neurons and results in their disfacilitation.8
The two processes cause reduced motor neuron activity
and a decrease in, or elimination of, tone in the postural
muscles (Figure2).58,64
The close association between the occurrence of cata-
plexy and orexin deficiency in patients with narcolepsy
and animal models of narcolepsy suggests that orexin
has a key role in the pathophysiology of cataplexy.2
The strength of the excitatory projections from orexin
neurons to the noradrenergic neurons in the locus coer-
uleus is thought to prevent cataplexy in healthy individ-
uals.65,66 In patients with narcolepsy or narcolepsy and
cataplexy, however, orexin deficiency reduces normal
levels of noradrenergic neuronal activity, which closely
correlates with cataplectic attacks in Hcrt–/– mice, and
dogs with narcolepsy.8,66 Drugs that increase noradrena-
line levels in the CNS are effective in alleviating cataplexy
in humans, dogs and mice.8,26,65 A study demonstrated
that the frequency of cataplectic attacks was reduced
when orexin receptors were restored to serotonergic
neurons in the dorsal raphe of mice lacking orexin
receptors, which suggests the serotonin signalling system
Table 1 | Cataplexy in humans and animal models
Features Human Mouse* Dog
Behavioural Postural collapse, jaw sagging,
weak knees
Postural collapse, falling prone
oronto their sides
Postural collapse, weakness
Level of
consciousness
Awake (memory of episode) Probably awake (response to
visual stimuli intact)
Awake (response to visual stimuli
intact)
Triggers Strong positive emotions
(forexample, laughter, joking,
elation)
Emotionally rewarding behaviours
(for example, eating palatable
food, running, social interaction)
Emotionally rewarding behaviours
(forexample, eating palatable food,
running, social interaction)
Duration of
cataplectic attach
Brief (seconds to minutes) Brief (seconds to minutes) Brief (seconds to minutes)
Cortical EEG Mixture of waking and
REM‑sleep‑like EEG
Mixture of waking and
REM‑sleep‑like EEG
Mixture of waking and REM‑sleep‑like
EEG
Muscle tone Muscle paralysis or weakness;
loss of EMG activity
Muscle paralysis; loss of EMG
activity
Muscle paralysis; loss of EMG activity
Therapy Suppressed by monoamine
reuptake blockers (for example,
antidepressants) and GHB
Suppressed by monoamine
reuptake blockers (for example,
antidepressants) and GHB
Suppressed by monoamine reuptake
blockers (for example, antidepressants)
but no response to GHB
*Hcrt–/– mouse model. Disruption of Hcr tr2. Abbreviations: EMG, electromyogram; GHB, γ‑hydroxybutyrate; REM, rapid eye movement.
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could also be involved in cataplexy.67 Previous work has
shown that activity of serotonergic neurons in the dorsal
raphe does not change during cataplexy, in contrast to
noradrenergic neurons in the locus coeruleus.65,68
Orexin A and orexin B are two different peptides
produced by 70,000–80,000 neurons in the healthy
hypothalamus in humans. Orexin neurons not only
strongly innervate and directly excite noradrener-
gic, dopaminergic, serotonergic, histaminergic and
cholinergic neurons, but also modulate the release
of glutamate and other amino acid transmitters.69,70
Behavioural studies revealed that orexin is released at
high levels during active waking, at intermediate or
low levels in quiet but alert waking periods and during
REM sleep, and at minimal levels in non-REM sleep.71,72
Electrophysiological recording of neuronal unit activ-
ity in narcoleptic dogs shows that most of the brain
regions involved in the generation of REM sleep atonia
are alsoinvolved in episodes of cataplexy.52,55,68,73 Thus,
at the neuronal level, these findings support the concept
of cataplexy as an intrusion of REM sleep paralysis into
wakefulness. Cataplexy is not identical to REM sleep,
however, the main difference being the maintenance
of consciousness. Preservation of activity of histamin-
ergic neurons during cataplexy but not in REM sleep
suggests a function for histamine in maintaining wake-
fulness during cataplectic episodes.66 Orexin neuron
activity and orexin release are absent during conditions
of quiet waking and drowsiness, but the cessation of
this neuronal activity is not sufficient enough to cause
cataplexy under normal physiological conditions; thus,
the absence of orexin neurons in narcolepsy or narco-
lepsy and cataplexy might be associated with other ana-
tomicaland physiological changes in the brain, perhaps
secondary to orexin malfunction.74–76 Accordingly, two
studies of histaminergic neurons in human narcolepsy
or narco lepsy and cataplexy indicated an increase in
numbers of these neurons, but this result differs from
results in animal models.77,78 The relationship between
changes in histaminergic neuronal numbers, cataplexy
and other symptoms of narcolepsy across different
species is unclear.
The amygdala has an important role in the process-
ing of emotional stimuli79 and, therefore, might also be
important in triggering cataplexy. Clinical and basic
research studies show that changes in neuronal activity
in the amygdala are associated with cataplexy. Functional
neuroimaging shows increased activity in the amygdala
while patients watch humorous photographic images,
and electrophysiological recordings from isolated cells
in narcoleptic dogs demonstrate that activity of certain
amygdalar neurons is closely associated with cataplec-
tic attacks.52,80 Another study indicates that bilateral
lesionsof the amygdala significantly reduce the fre-
quency ofcataplectic attacks in Hcrt –/– mice.41 A popula-
tion of GABAergic neurons in the amygdala innervates
the locus coeruleus, lateral pontine tegmentum (LPT)
and ventro lateral periaqueductal grey (vlPAG), the
functions of which are to support muscle tone during
wakefulness.41 Lesions in the LPT and vlPAG in rodents
cause sporadic bouts of muscle paralysis during wakeful-
ness that resemble cataplectic attacks, and inactivity of
locus coeruleus neurons is associated with muscle atonia
during cataplexy.8,66,81,82 In patients experiencing positive
emotions, therefore, GABAergic neurons in the amyg-
dala might become active and in turn inhibit the activity
of cells in the locus coeruleus, LPT and vlPAG that would
normally maintain waking postural tone.
The medial prefrontal cortex (mPFC) also has a role
in triggering cataplexy. Ingestion of palatable foods (for
example, chocolate), which trigger cataplexy in Hcrt–/–
mice, also activates neurons in the mPFC, and inhibition
of mPFC neurons markedly reduces cataplectic attacks
associated with positive emotional stimuli.83 In addition,
neurons in the mPFC innervate the amygdala and lateral
hypothalamus, which contain neurons that are active
during cataplexy and might innervate brainstem regions
involved in the regulation of muscle tone.
Treatment
The inhibitory effect of various antidepressants on the
adrenergic system is supported by invivo and invitro
studies.84 The dopaminergic system is involved in the
regulation of cataplexy via the D2-like receptor inmouse
models of narcolepsy. The frequency of cataplectic
attacks in these mice increases after D2-like recep-
tor activation, and decreases after receptor blockade.85
Cholinergic systems are also thought to be important in
the regulation of cataplexy in animal models, with stim-
ulation of the cholinergic system severely aggravating
canine cataplexy.86
The effectiveness of drugs used to treat cataplexy is
difficult to evaluate, as the methods employed to assess
the frequency and intensity of attacks—for example,
recall history, scale, diaries or video recordings—vary
from one study to another. Some patients might exhibit
a decrease in frequency and severity of cataplectic attacks
with disease duration. Behavioural measures such as cog-
nitive behavioural therapy might be of interest for some
patients to enable them to either control their emotion or
learn to avoid situations that trigger cataplectic attacks,
but this approach is not usually sufficiently effective to
be considered as a recommended treatment.
Antidepressants
Antidepressants and γ-hydroxybutyrate (GHB, also
known as sodium oxybate) are reportedly the most effec-
tive drugs to treat cataplexy (Table2).87 Neither tricyclic
agents nor selective serotonin reuptake inhibitors (SSRIs)
or selective norepinephrine reuptake inhibitors (SNRIs)
are approved by the European Medicines Agency or the
FDA for the treatment of cataplexy in children or adults.
This practice is based only on expert opinion, as no
studies demonstrating efficacy and safety of these drugs
for this indication have been carried out.
Tricyclic agents, which were the first drugs used to
treat cataplexy,87,88 are nonspecific monoamine reuptake
inhibitors that increase the availability of serotonin,
noradrenaline and, in some cases, dopamine.88 Some
tricyclic agents also have anticholinergic properties,
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which might contribute to their anticataplectic effect.
Clomipramine is the most widely used tricyclic agent
to treat cataplexy.87 Often, these agents have an effect
on cataplexy within 48 h at doses below those required
to treat depression, but tolerance frequently develops.
Cataplexy rebound, or status cataplecticus, which is
defined by an increase in the number of attacks and
the severity of cataplexy, typically occurs if antidepres-
sant intake, especially tricyclic agents, is interrupted or
abruptly halted.
Monoamine oxidase inhibitors (MAOIs) increase
the availability of the monoamine neurotransmitters,
for example, dopamine, noradrenaline and serotonin.
Studies have indicated that MAOIs (specifically, sele-
giline hydrochloride) strongly suppress REM sleep and
reduce the frequency of cataplectic attacks, but these
drugs are now rarely used because they are associated
with serious adverse effects.87
SSRIs (fluoxetine, paroxetine and citalopram),
although less effective than tricyclic antidepressants in
decreasing the frequency of cataplectic attacks, are widely
used for this purpose, and the frequency of associ ated
adverse effects is lower than for tricyclic agents. SSRIs,
and SNRIs (such as venlafaxine, duloxetine and milnacip-
ran), are the antidepressants most widely used to treat
cataplexy, particularly venlafaxine as it is effective within
48 h.87 Due to the short duration of action of venlafaxine,
the extended-release form seems to be preferable, start-
ing at a low dose (37.5 mg) but higher doses are often
needed (75–300 mg). Venlafaxine is not recommended
for treatment in pregnant women with narcolepsy, but
has an acceptable tolerance profile for use in children.89,90
The differential efficacy of venlafaxine on either ‘nega-
tive’ (hypotonia) or ‘active’ motor components during
cataplexy is unknown. Other SNRIs, such as duloxetine
and milnacipran, or noradrenaline reuptake inhibitors,
such as viloxazine, reboxetine, atomoxetine and bupro-
pion, seem to be promising treatments in decreasing the
frequency of cataplectic attacks, are well tolerated, and
have a mild stimulant effect.91,92
γ‑Hydroxybutyrate
GHB is a natural metabolite of γ-aminobutyrate and func-
tions as a neurotransmitter at the GHB receptor (GHBR;
also known as solute carrier family 52, riboflavin trans-
porter, member 2) at physiological concentrations and as a
GABA receptor agonist at pharmacological concentrations,
and also modulates dopaminergicsignalling.93
GHB is effective at reducing both the frequency and
intensity of cataplectic attacks, as well as restoring noc-
turnal sleep continuity and reducing EDS in patients
with narcolepsy or narcolepsy and cataplexy.93–95 Despite
a half-life of only 40–60 min, its clinical benefit persists
well beyond this period, and with nightly use the benefit
is significant after 4weeks, highest after 8weeks, and
maintained during long-term therapy.94,95 GHB also has
an acceptable tolerance profile for treatment of children;
however, as for venlafaxine, its relative efficacy on negative
versus active components of cataplexy is unknown.89 It ca n
also be used with antidepressant or stimulant therapy, but
should not be used in conjunction with alcohol.95 Unlike
antidepressants, interruptionof treatment with GHB does
not result in a rebound ofcataplexy. One major issue with
the use of GHB is its nonmedical use, as it is sometimes
used in athletes for performance enhancement owing to
its metabolic effects. Safety data and clinical experience of
GHB therapy indicate that the potential for misuse is low
in patients withnarcolepsy.95,96,97
Effects of stimulants
Drugs that increase adrenergic and dopaminergic
signalling, such as amphetamines, methylphenidate
hydro chlor ide and mazindol (but not modafinil), also
decrease the frequency of cataplectic attacks. Although
rarely used in practice, mazindol is a tricyclic, anorec-
tic, nonamphetamine that is a very effective stimulant
(half-life 10 h) and is also effective in the treatment of
cataplexy.95 A careful cardiological follow-up is required
Table 2 | Therapies for cataplexy
Mode of action Treatment Dose
First line
GABAB agonist that
modulates dopamine
neurotransmission
GHB 6–9 g per night*
Norepinephrine and
serotonin reuptake
inhibitor
Venlafaxine 37.5–300.0 mg
perday
Selective serotonin
reuptake inhibitors
Fluoxetine
Citalopram
20–60 g per day
20–40 mg per day
Tricyclic
antidepressants
Clomipramine
Protriptyline
10–20 mg per day
5–10 mg per day
Second line
Tricyclic
antidepressants
Clomipramine
Protriptyline
30–100 mg per day
20–80 mg per day
Norepinephrine and
serotonin reuptake
inhibitor
Duloxetine 30–120 mg per day
Norepinephrine
reuptake inhibitors
Reboxetine
Atomoxetine
2–10 mg per day
2–10 mg per day
Third line
Tricyclic, anorectic,
nonamphetamine
stimulant
Mazindol 1–4 mg per day
Monoamine oxidase
inhibitor
Selegiline 20–40 mg per day
Future therapies
GABAB agonist GHB
slow‑release
6–9 g per night*
NA Immune‑based
therapy at
disease onset
Intravenous
immunoglobulin,
plasmapheresis or
monoclonal antibodies
NA Orexin,
orexinagonists
or orexin‑
expressing cell
transplantation
NA
*GHB is the first and only medication indicated for cataplexy. Abbreviations:
GABAB, γ‑aminobutyric acid type B receptor; GHB, γ‑hydroxybutyrate; NA, not
applicable.
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with mazindol and amphetamines. Mazindol has less
potential for misuse and development of tolerance than
amphetamines in patients with narcolepsy.
Future therapeutic management
Orexin deficiency underlies the pathophysiology of cata-
plexy; therefore, orexin replacement therapy could be
an effective strategy. In humans, the use of orexin-based
treatment has been disappointing; however, there has
been some success with this approach in treating cata-
plexy in dogs.98,99 Intraventricular delivery of orexinA
has potential efficacy, but is probably inappropriate for
long-term therapy. Intranasal delivery to bypass the
blood–brain barrier is a noninvasive method to deliver
orexin to the brain. This method has been shown to
improve cognition and olfactory performance and stabi-
lize sleep in rhesus monkeys and patients with narco-
lepsy or narcolepsy and cataplexy, but has not been tested
for its effects on cataplexy alone.100–103 Synthetic orexin
receptor agonists might be another treatment option.
Transplantation of orexin neurons might, theoretically,
provide a cure for patients with narcolepsy, even if the
results of neuronal transplantation in other diseases have
been disappointing, with graft rejection and low survival
rates of the implant.104,105
The activation of histaminergic neurons by an inverse
agonist of the histamine H3 receptor, which is presyn-
aptic and enhances histamine release, is a promising
therapy. One of these compounds, pitolisant, improved
wakefulness in normal animals, blocked abnormal tran-
sition from wakefulness to REM sleep in Hcrt–/– mice,
and decreased sleepiness and might have the potential to
treat cataplectic attacks in patients with narcolepsy.106,107
Finally, on the basis of the immune-mediated hypoth-
esis for the loss of orexin neurons, we suggest that
immuno therapies at disease onset might modify the
long-term disease outcome if the ‘autoimmune’ process
that targets orexin neurons is not too advanced and
can be partially reversed. Corticosteroids, intravenous
immunoglobulin, plasmapheresis, immunoadsorption
and alemtuzumab have all been tested in the treatment of
cataplexy, with variable efficacy.108–112 In one patient who
had undetect able levels of orexin in the CSF, intravenous
immunoglobulin treatment only 15days after disease
onset resulted in clinical improvement of cataplexy and
biological normalization of CSF orexin A levels.113 At the
onset of narcolepsy, high doses of immunomodulators
might downregulate T-cell functions and pathogenic
cytokines and interfere with autoantigen recognition
through HLA-DQB1*06:02 expression during induc-
tion therapy.114 Well-designed trials of immunotherapies
in patients at the onset of disease are needed; however,
an improved understanding of the pathophysiology of
orexin neuron loss is also required to develop effective
treatment strategies.
Conclusions
Cataplexy is the pathognomonic symptom of narcolepsy,
but is underdiagnosed as a symptom as it varies pheno-
typically in terms of age of onset, affected muscle group,
trigger factors, frequency and intensity. Cataplexy results
from the inappropriate activation during wakefulness of
the brainstem circuits that normally generate muscle
atonia during REM sleep. The pathological intrusion
of REM sleep paralysis into wakefulness occurs almost
exclusively when orexin neurons are depleted. Neurons
expressing orexin normally serve to drive and synchro-
nize the activity of monoaminergic and cholinergic
neuro nal systems. The loss of an excitatory noradrener-
gic drive onto motor neurons underlies the loss of pos-
tural muscle tone during cataplexy. Involvement of the
amygdala and medial prefrontal cortex is highlighted by
the triggering of cataplectic attacks by emotional stimuli
and processing thereof.
To overcome the consequences of narcolepsy and
cataplexy, early diagnosis and treatment of patients are
essential. Despite a major advance in our understand-
ing of the neurobiology of narcolepsy–cataplexy, there
is no cure. Current therapeutic management is only
sympto matic, with widespread use of antidepressants
and GHB to reduce the frequency of cataplectic attacks.
The discovery of orexin deficiency in humans has ledto
a new diagnostic test for narcolepsy and might lead
toorexin replacement therapy. Future therapeutic targets
must be focused on immunotherapies at early stages in
the disease to prevent the loss of orexin neurons and
diseaseprogression.
Review criteria
Articles were identified from publications listed in English
on PubMed from January 1970 to October 2013. The
following keywords were used alone and in combination:
“narcolepsy”, “cataplexy”, “REM sleep”, “atonia”,
“motoneuron”, “amygdala”, “emotions”, “hypocretin”,
“orexin”, “dog”, “mouse”, “mice”, “brainstem”, “locus
coeruleus”, “noradrenergic”, “arousal” and “neurobiology”.
Publications were also identified through the authors’
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Author contributions
Y.D. researched data for the article. Y.D., J.M.S. and
J.H.P. wrote the article and substantially contributed
to discussion of the content. Y.D., J.M.S., R.L., Z.A.T.
and J.H.P. reviewed and/or edited the manuscript
before submission.
Supplementary information is linked to the online
version of the paper at www.nature.com/nrneurol.
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... Aside from pitolisant and the oxybates, no agents are approved by the FDA for the treatment of narcolepsy-associated cataplexy. However, some classes of antidepressants are used off-label, specifically the selective serotonin reuptake inhibitors (SSRIs) and selective norepinephrine reuptake inhibitors (SNRIs) [97]. ...
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Narcolepsy is a chronic neurologic disorder associated with the dysregulation of the sleep–wake cycle that often leads to a decreased quality of life and results in a considerable health burden. There is often a delay to diagnosis of narcolepsy, mainly due to the lack of recognition of this disorder. One of the main factors hindering the diagnosis of narcolepsy is the association of comorbidities, which include other sleep disorders, psychiatric disorders, cardiovascular disorders, and metabolic disorders. The signs and symptoms of these comorbidities often overlap with those of narcolepsy, and some of the medications used for their treatment may obscure the symptoms of narcolepsy, leading to a delay in diagnosis. This review is targeted to clinicians unaccustomed to working with sleep disorders and aims to increase recognition and improve the management of narcolepsy.
... Pitolisant is a selective histamine 3 (H 3 )-receptor antagonist/inverse agonist that increases the synthesis and release of histamine in the brain via competitive binding to presynaptic H 3 autoreceptors [21,24]. Pitolisant also binds to H 3 receptors on nonhistaminergic neurons [25][26][27], which increases the activity of other neurotransmitters that promote wakefulness (e.g., acetylcholine, dopamine, norepinephrine) [18] and play a role in the control of cataplexy (e.g., norepinephrine, serotonin) [28,29]. In contrast to stimulant medications, pitolisant does not increase dopamine release in brain regions of the reward system (e.g., nucleus accumbens) in animal studies [30] and demonstrates minimal to no potential for abuse in humans [31]. ...
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Background Pitolisant is approved in the USA and Europe for the treatment of excessive daytime sleepiness or cataplexy in adults with narcolepsy.Objective Analyses evaluated the time to onset of clinical response during treatment with pitolisant.Methods Data were obtained from two randomized, double-blind, 7-week or 8-week, placebo-controlled studies (HARMONY 1, HARMONY CTP). Study medication was individually titrated to a maximum dose of pitolisant 35.6 mg/day and then remained stable. Efficacy assessments included the Epworth Sleepiness Scale and weekly rate of cataplexy (calculated from patient diaries). Onset of clinical response was defined as the first timepoint at which there was statistical separation between pitolisant and placebo.ResultsThe analysis included 61 patients in HARMONY 1 (pitolisant, n = 31; placebo, n = 30) and 105 patients in HARMONY CTP (pitolisant, n = 54; placebo, n = 51). Onset of clinical response began at week 2 (HARMONY 1) or week 3 (HARMONY CTP) for the mean change in Epworth Sleepiness Scale score, and week 2 (HARMONY CTP) or week 5 (HARMONY 1) for the mean change in weekly rate of cataplexy, with further improvements observed in pitolisant-treated patients through the end of treatment. The percentage of treatment responders was significantly greater with pitolisant vs placebo beginning at week 3 for excessive daytime sleepiness (defined as an Epworth Sleepiness Scale score reduction ≥ 3) and week 2 for cataplexy (defined as a ≥ 50% reduction in weekly rate of cataplexy [HARMONY CTP]).Conclusions Onset of clinical response for excessive daytime sleepiness and/or cataplexy was generally observed within the first 2–3 weeks of pitolisant treatment in patients with narcolepsy.ClinicalTrials.gov identifierNCT01067222 (February 2010), NCT01800045 (February 2013).
... In narcolepsy, significant changes in motor control during sleep may be expressed as REM without atonia and often relevant clinical outcomes in many patients [19]. Cataplexy, defined as a sudden uncontrolled musculature weakness triggered by emotions during wakefulness, such as laughing, is a sleeprelated phenomenon associated with disturbed muscular control during REM [12,20]. These conditions can be preceded by changes, either subtle or pronounced, within the orofacial musculature [11,12,21,22]. ...
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Purpose Sleep is a crucial component of life, characterized by global behavioral and neurochemical inhibition of brain activity. The gold-standard measurement of sleep is polysomnography (PSG). It assesses several organic functions during sleep, embracing brain activity, eyes movements, muscular pattern, and heart rhythm. Despite motor function being reduced during all sleep stages, particular muscular groups remain active, including those involved in respiratory or eye movement control. Polysomnography depends on this residual muscle activity to achieve reliable sleep recordings. Any interference with mechanisms dictating this behavior might impact electrogenic patterns in PSG, therefore, affecting clinical conclusions. There is a lack of knowledge about the association between myofunctional patterns during sleep and the widely prescribed cosmetic procedure of botulinum neurotoxin (BoNT). Considering aesthetical purposes, BoNT injection is often used to minimize facial wrinkles, through a reduction on the tonus of target muscles via cholinergic pathways. This review aimed to raise two important and clinically pertinent questions: (1) would the muscular hypotonicity caused by treatment with BoNT affect PSG patterns?; (2) could this change the way sleep looks like after BoNT-based cosmetic treatment challenging the effective use of standard PSG scoring criteria? Methods A critical review of the literature currently available in the PubMed electronic database was undertaken. Results This review confirmed the lack of data regarding the possible consequences of the cosmetic use of BoNT on PSG reading and interpretation. We propose putative mechanisms and pathways by which this treatment could have these effects with clinically relevant impact on diagnosis of sleep disturbances. Conclusions Even though there is little evidence on the relationship between cosmetic use of BoNT and substantial changes on sleep related motor control, it is reasonable to hypothesize that this may impact PSG patterns and its interpretation. As the use of this drug is rising, as well as there is an increase on the prevalence of sleep disturbances needing PSG diagnosis, this should be a relevant subject warranting future research.
... Cataplexy is defined as a sudden loss of muscle tone during wakefulness [1,2] and is triggered by strong emotions (e.g., laughter in humans, sound of a barking dog in sheep, food in dogs, or exploration and exposure to palatable treats in mice and rats) [3]. Narcolepsy with cataplexy affects up to 0.05% of the adult population [4]. The disease is also a known pathology of several domesticated animal species, including dog, sheep and horse. ...
Article
Cataplexy is the pathognomonic and the most striking symptom of narcolepsy. It has originally been, and still is now, widely considered as an abnormal manifestation of rapid eye movement (REM) sleep during wakefulness due to the typical muscle atonia. The neurocircuits of cataplexy, originally confined to the brainstem as those of REM sleep atonia, now include the hypothalamus, dorsal raphe (DR), amygdala and frontal cortex, and its neurochemistry originally focused on catecholamines and acetylcholine now extend to hypocretin (HCRT) and other neuromodulators. Here, we review the neuroanatomy and neurochemistry of cataplexy and propose that cataplexy is a distinct brain state that, despite similarities with REM sleep, involves cataplexy-specific features.
... Consequently, NT1 patients are usually diagnosed 10e15 years after symptoms onset [4], resulting in detrimental effect on the children's learning and psychological development, weighting significantly on the already substantial burden that patients bear [5]. Cataplexy is thought to result from activation during wakefulness of the sleep circuitry involved in REM sleep that lead to reduced skeletal motor neuron activity via increased inhibitory and reduced excitatory signals [6]. Conversely, the cold stimulus benefit observed in disorders of the neuromuscular junction results from reduced acetylcholinesterase activity which leads to higher acetylcholine levels at the neuromuscular junction. ...
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Background: Lower-sodium oxybate (LXB) is an oxybate medication with the same active moiety as sodium oxybate (SXB) and a unique composition of cations, resulting in 92% less sodium. LXB was shown to improve cataplexy and excessive daytime sleepiness in people with narcolepsy in a placebo-controlled, double-blind, randomized withdrawal study (NCT03030599). Additional analyses of data from this study were conducted to explore the effects of LXB on cataplexy, including the clinical course and feasibility of transition from other anticataplectics to LXB monotherapy. Objective: The aim of these analyses was to evaluate cataplexy frequency during initiation/optimization of LXB and taper/discontinuation of prior antidepressant/anticataplectic medications. Methods: Eligible participants (adults aged 18-70 years with narcolepsy with cataplexy) entered the study taking SXB only (group A), SXB + other anticataplectics (group B), or anticataplectic medication other than SXB (group C), or were cataplexy-treatment naive (group D). LXB was initiated/optimized during a 12-week, open-label, optimized treatment and titration period (OLOTTP). Other anticataplectics were tapered/discontinued during weeks 3-10 of OLOTTP. A 2-week stable-dose period (SDP; during which participants took a stable dose of open-label LXB) and 2-week double-blind randomized withdrawal period (during which participants were randomized to continue LXB treatment or switch to placebo) followed OLOTTP. Treatment-emergent adverse events (TEAEs) were recorded throughout the duration of the study. Results: At the beginning of OLOTTP, median weekly cataplexy attacks were lower in participants taking SXB at study entry (SXB only [2.00]; SXB + other anticataplectics [0.58]) versus participants who were taking other anticataplectics (3.50) or were anticataplectic naive (5.83). Median weekly cataplexy attacks decreased during weeks 1-2 of OLOTTP in all groups. Increased cataplexy frequency was observed in participants tapering/discontinuing other anticataplectics during weeks 3-10 and was more prominent in participants taking other anticataplectics alone compared with those taking SXB plus other anticataplectics. Cataplexy frequency decreased throughout initiation/optimization in anticataplectic-naive participants. Median number of cataplexy-free days/week at the end of SDP (study week 14) was similar in all groups (6.0, 6.1, 6.0, and 6.2 in groups A, B, C, and D, respectively). During OLOTTP and SDP, TEAEs of worsening cataplexy were reported in 0%, 47.8%, 16.7%, and 2.2% of participants in groups A, B, C, and D, respectively; most TEAEs of worsening cataplexy were reported during tapering/discontinuation of other anticataplectics. Conclusions: LXB monotherapy was effective in reducing cataplexy and increasing cataplexy-free days. These results illustrate the feasibility of switching from SXB to LXB while tapering/discontinuing other anticataplectics. Trial registration: A Study of the Efficacy and Safety of JZP-258 in Subjects With Narcolepsy With Cataplexy; https://clinicaltrials.gov/ct2/show/NCT03030599 ; clinicaltrials.gov identifier: NCT03030599.
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This article addresses the clinical presentation, diagnosis, pathophysiology and management of narcolepsy type 1 and 2, with a focus on recent findings. A low level of hypocretin‐1/orexin‐A in the cerebrospinal fluid is sufficient to diagnose narcolepsy type 1, being a highly specific and sensitive biomarker, and the irreversible loss of hypocretin neurons is responsible for the main symptoms of the disease: sleepiness, cataplexy, sleep‐related hallucinations and paralysis, and disrupted nocturnal sleep. The process responsible for the destruction of hypocretin neurons is highly suspected to be autoimmune, or dysimmune. Over the last two decades, remarkable progress has been made for the understanding of these mechanisms that were made possible with the development of new techniques. Conversely, narcolepsy type 2 is a less well‐defined disorder, with a variable phenotype and evolution, and few reliable biomarkers discovered so far. There is a dearth of knowledge about this disorder, and its aetiology remains unclear and needs to be further explored. Treatment of narcolepsy is still nowadays only symptomatic, targeting sleepiness, cataplexy and disrupted nocturnal sleep. However, new psychostimulants have been recently developed, and the upcoming arrival of non‐peptide hypocretin receptor‐2 agonists should be a revolution in the management of this rare sleep disease, and maybe also for disorders beyond narcolepsy.
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Aims: To study incident narcolepsy in first- and second-generation immigrant groups using Swedish-born individuals and native Swedes as referents. Methods: The study population included all individuals registered and alive in Sweden at baseline. Narcolepsy was defined as having at least one registered diagnosis of narcolepsy in the Swedish National Patient Register. The incidence of narcolepsy in different immigrant groups was assessed by Cox regression, with hazard ratios (HRs) and 95% confidence intervals (CI). The models were stratified by sex and adjusted for age, geographical residence in Sweden, educational level, marital status, co-morbidities, and neighbourhood socioeconomic status. Results: In the first-generation study, 1225 narcolepsy cases were found; 465 males and 760 females, and in the second-generation study, 1710 cases, 702 males and 1008 females. Fully adjusted HRs (95% CI) in the first-generation study was for males 0.83 (0.61-1.13) and females 0.83 (0.64-1.07), and in the second-generation study for males 0.76 (0.60-0.95) and females 0.91 (95% CI 0.76-1.09). Statistically significant excess risks of narcolepsy were found in first-generation males from North America, and second-generation males with parents from North America, and second-generation females with parents from Latin America. Conclusions: There were only significant differences in incident narcolepsy between native Swedes and second-generation male immigrants. The observed differences can partly be explained by differences in Pandemrix® vaccinations and are probably not attributable to genetic differences between immigrants and natives.
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There is currently a lack of clinical research that would strongly support the application of CBT in the treatment of narcolepsy type 1. Despite that, there are several guidelines that suggest some techniques should be routinely applied. Currently, there is still a lack of results on what to do with patients who have comorbid sleep and psychiatric disorders or other psychosocial comorbidities and problems. This case study concerns a 27-year-old female who had narcolepsy type 1 and history of sleep, psychosocial, and psychiatric problems. Her main problems included cataplexy, daily tiredness and sleepiness, a problem with daily physical activity, and problems in her psychosocial functioning. The patient received 7 session of CBT treatment based on recommended techniques for patients with hypersomnia. Self-reported measure of sleep, anxiety, and depression were collected at the start and 1-month post-treatment. Objective psychological measures recorded positive changes in post-treatment assessment of CBT effect on her sleep pattern, significant reduction of cataplexy, depressive and anxiety symptoms, daily activity, and tiredness during the day.
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Narcolepsy is a sleep disorder manifesting symptoms such as excessive daytime sleepiness and often cataplexy, a sudden and involuntary loss of muscle activity during wakefulness. The underlying neuropathological basis of narcolepsy is the loss of orexin neurons from the lateral hypothalamus. To date numerous animal models of narcolepsy have been produced in the laboratory, being invaluable tools for delineating the brain circuits of narcolepsy. This review will examine the evidence regarding the function of the orexin system, and how loss of this wake-promoting system manifests in excessive daytime sleepiness. This review will also outline the brain circuits controlling cataplexy, focusing on the contribution of orexin signaling loss in narcolepsy. Although our understanding of the brain circuits of narcolepsy has made great progress in recent years, much remains to be understood.
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Study objectives To investigate potential stimulant and anticataplectic effects of 10 mg reboxetine in patients diagnosed with narcolepsy. Design 12 patients were treated for a 2-week period with 10 mg reboxetine under open conditions. The dosage of reboxetine was gradually increased between Day 1 and Day 9. Outcome parameters consisted of nightime polysomnography (PSG), Multiple Sleep Latency Test (MSLT), Epworth Sleepiness Scale (ESS), Visual Analog Scale for Sleepiness (VAS), Ullanlinna Narcolepsy Scale (UNS), and the Beck Depression Inventory (BDI). Setting Sleep Disorders Clinic at a University Hospital. Patients 12 patients meeting ICSD-criteria for narcolepsy. Interventions Pharmacological treatment with reboxetine. Results Following treatment for two-weeks, a significant improvement in daytime sleepiness could be observed, as reflected by a mean decrease of 48.6% on the Epworth Sleepiness Scale and a mean increase of 54.7% in sleep latency on the MSLT. Furthermore, a significant reduction in the cataplexy subscore of the Ullanlinna Narcolepsy Scale and in REM-sleep was found. Conclusions Our results suggest that reboxetine exerts stimulant and anticataplectic effects in narcolepsy. Contrary to previous thinking, by which stimulant action would require dopaminergic facilitation, noradrenergic mechanisms might be relevant to the control of wakefulness.
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Study Objectives: To evaluate and compare the efficacy and safety of three doses of sodium oxybate and placebo for the treatment of narcolepsy symptoms. Design: A multicenter, double blind, placebo-controlled trial. Setting: N/A Participants: Study subjects were 136 narcolepsy patients with 3 to 249 (median 21) cataplexy attacks weekly. Interventions: Prior to baseline measures, subjects discontinued anticataplectic medications. Stable doses of stimulants were permitted. Subjects were randomized in blinded fashion to receive 3, 6, or 9 g doses of sodium oxybate or placebo taken in equally divided doses upon retiring to bed and 2.5-4 hours later for 4 weeks. Measurements and Results: Disease symptoms and adverse events were recorded in daily diaries. The primary measure of efficacy was the change from baseline in weekly cataplexy attacks. Secondary measures included daytime sleepiness using the Epworth Sleepiness Scale (ESS), inadvertent daytime naps/sleep attacks and nighttime awakenings. Investigators assessed changes in disease severity using Clinical Global Impression of Change (CGI-c). Compared to placebo, weekly cataplexy attacks were decreased by sodium oxybate at the 6 g dose (p=0.0529) and significantly at the 9 g dose (p=0.0008). The ESS was reduced at all doses, becoming significant at the 9 g dose (p=0.0001). The CGI-c demonstrated a dose-related improvement, significant at the 9 g dose (p=0.0002). The frequency of inadvertent naps/sleep attacks and the nighttime awakenings showed similar doseresponse trends, becoming significant at the 9 g dose (p=0.0122 and p=0.0035, respectively). Sodium oxybate was generally well-tolerated at all three doses. Nausea, headache, dizziness and enuresis were the most commonly reported adverse events. Conclusions: Sodium oxybate significantly improved symptoms in patients with narcolepsy and was well tolerated.
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