Volume 11 • Number 1 • March 2003 | ACO
This article is the first in a series of articles dealing with
risk management in the practise of chiropractic and
osteopathy, prepared by the COCA Risk Management
Although rare, vertebrobasilar stroke is the best known of
the possible side effects of cervical manipulation. Due to
the serious sequelae that may result from cervical
manipulation, chiropractors and osteopaths must take the
appropriate steps to ensure the risk is minimised. This article
outlines how the astute practitioner can minimise this risk.
Practitioners must decide on the options for treatment of a
patient with neck problems. Practitioners must also advise
the patient of these options as part of an appropriate informed
Of all the complications associated with spinal manipulative
therapy (SMT), vertebrobasilar stroke (VBS) is by far the
best known and may result in devastating neurological
sequelae, including death. It appears that in rare instances
SMT applied to the cervical spine may damage the vertebral
artery (VA) or carotid artery (CA), leading to arterial
dissection or vasospasm. These events stimulate thrombus
formation, which in turn may occlude blood vessels in this
region of the arterial tree.
In spite of extensive investigations the exact mechanism by
which SMT is thought to produce arterial damage is not fully
understood. However, it is thought that with a thorough
patient clinical history and physical examination, combined
with judicially applied cervical spine techniques, the risk of
this complication may be significantly reduced.
In the first instance, practitioners must decide on the options
for treatment of a patient with neck problems. Practitioners
must also advise the patient of these options as part of an
appropriate informed consent. Manipulation/adjustment is
but one option, with alternatives including mobilisation,
traction, PNF/muscle energy, massage techniques and
electrotherapy (including ultrasound, interferential and
TENS). These ‘other’ techniques are not known to produce
serious events such as stroke, and therefore should be
considered as options in the treatment of neck pain. A recent
randomised controlled trial of 336 neck pain patients
concluded ‘Cervical spine manipulation and mobilization
yield comparable clinical outcomes.’ The investigators added,
‘Given the risk of serious – though rare – complications
resulting from cervical spine manipulation, chiropractors
should consider mobilization as an effective treatment option
for their neck pain patients.’1.
The incidence of VBS associated with SMT has been the
subject of numerous research papers and for serious
complications, has been reported as being as low as one in
14 million manipulations2, to as high as one in 4,500 cervical
In a recent Canadian study, it was reported that for every
100,000 persons aged less than 45 years, 1.3 cases of VBS
Risk Management for Chiropractors and Osteopaths:
Neck Manipulation & Vertebrobasilar Stroke
J ohn Reggars D.C., M.Chiro.Sc.
Simon French B.App.Sc.(Chiro.)., M.P.H.
Bruce Walker D.C., M.P.H.
Melainie Cameron B.App.S c.(Osteo.)., M.H.S c.
Henry Pollard Ph.D., B.Sc., Grad.Dip.Chiro., Grad.Dip.App.Sc., M.Sport.Sc.
Andrew Vitiello B.Sc., M.Chiro.
Peter Werth B.App.S c.(Chiro.).
Cent re f or Clinical Ef f ect iveness
Monash Inst it ut e of Healt h Services Research
Monash Medical Cent re
Locked Bag 29
CLAYTON VIC 3168, Aust ralia
Phone: ( +61 3) 9594 7526
Fax: ( +61 3) 9594 7552
Email: simon. f rench@med. monash. edu. au
Original Articles: Reviews & Experimental
attributable to chiropractic would be observed within 1 week
of their manipulation4.
Anecdotal Australian data is revealing. In a recent letter to
the Chiropractors’ Association of Australia (CAA)
membership, the President of the CAA, in conjunction with
its Professional Indemnity insurer Guild Insurance Limited
(personal correspondence 23/10/01), reported an
unprecedented 12 cases in 6 months of alleged chiropractic
manipulation related VBS. The CAA has a membership of
approximately 1500 chiropractors and if we assume that each
chiropractor sees 100 patients per week, this would equate
to a total of 150,000 patient visits per week and 7.8 million
visits per year. Assuming 50% of those patients receive SMT
to the cervical spine, for a six month period the total number
of patients receiving cervical spine manipulation would be
1,950,000. Therefore, on this basis the risk of a chiropractic
patient experiencing a VBS associated with SMT would be
1,950,000 divided by 12 or one in 162,500 patient visits.
However, this calculation is based on anecdotal data only.
The exact risk of SMT related VBS is extremely difficult to
It is well known that many of these complications are never
reported and therefore fail to be included in the scientific
literature, but it is generally agreed that the risk is far greater
than the published studies suggest5.
According to Terrett2, the majority of those who suffered an
SMT related VBS are in the 30 to 45 year age group. This
data would tempt the conclusion that degenerative vascular
or osseous changes are not a risk factor for SMT related
arterial damage. However, this predilection for a younger
age group could simply be a reflection of the age distribution
of the population seeking manipulative therapy. Similarly a
greater risk for females to have post SMT related VBS has
also been postulated, but this may also reflect a gender
difference in health care utilisation.
Table 1 outlines other known potential risk factors for SMT
related VBS. However, as Terrett2 suggests, patients who
suffer VBS or stroke like symptoms following cervical
manipulation are generally young healthy adults, have an
uneventful medical history and have none, or only a few, of
the stroke risk factors.
A recent review of 64 medicolegal records describing
cerebrovascular ischaemia after cervical SMT concluded
‘Cerebrovascular accidents after manipulation appear to be
unpredictable and should be considered an inherent,
idiosyncratic and rare complication of this treatment
Genetic testing has been mooted as an investigation for
determining those patients at a higher risk of cardiovascular
disease7. It is postulated that those patients carrying a
mutation in the MTHFR gene (which increases homocysteine)
are at higher risk of heart disease, deep vein thrombosis and
stroke. The usefulness of this test in chiropractic and
osteopathic practices for screening those patients who may
be at a higher risk of VBS is speculative at this stage.
Mechanisms of Vertebral Artery
It is not within the scope of this article to provide a detailed
anatomical description of the cervico-cerebral circulation.
However, a brief description is warranted to explain the
mechanism of injury to the VA’s. Also, recent research has
implicated SMT in the damage of the carotid arteries8.
Table 2 outlines the four anatomical sections of the VA. The
two VA’s are anatomically divided into 4 sections from their
origin on the subclavian arteries. Although VA injury has
been reported in all anatomical sections, by far the most VBS
and stroke like symptoms occur from events within Section
3 of the artery. This is thought to be due in part to a lack of
free movement of the artery at that level. Fibrous tethering
of the VA during cervical rotation causes the VA to be
stretched, compressed and torqued2.
Cadaveric studies have shown that the VA will elongate on
average 4.7 mm on cervical rotation and 5.8 mm on lateral
flexion9. Cervical rotation elongates both the contralateral
and the ipsilateral VA and at 30º of rotation, the contralateral
VA kinks as it exits the C2 transverse foramen10, while the
ipsilateral VA kinks and elongates at 45º of rotation11.
Stretching of the artery in this way reduces its lumen
Table 1. Potential risk factors for SMT related VBS14, 30.
Previous history of ischaemic symptoms
Dizziness from head movements
Anomalous cerebral circulation
Connective tissue disease
Family history of stroke
Volume 11 • Number 1 • March 2003 | ACO
diameter12 causing altered haemodynamics, such as
turbulence or haemostasis, both of which can result in
It has therefore been suggested that SMT to the cervical spine
utilising less than 30º rotation reduces mechanical stress on
the artery and therefore the risk of VA injury2,14.
In another study on artery deformation in relation to neck
position, the research suggests that cervical rotation combined
with extension and traction may obstruct flow in either VA13.
However, it must also be remembered that no studies to date
have investigated the biomechanical and/or pathological
effects of the SMT thrust techniques on the VA. Therefore,
even when SMT is delivered to the lower cervical spine, there
is still a potential risk of VBS.
Spontaneous VA dissection has also been implicated as a
possible cause of SMT related VBS. The annual incidence
of spontaneous VA dissection has been estimated at one to
1.5 per 100,000, while spontaneous dissections of both the
carotid artery and the VA accounts for 2 percent of all
ischaemic strokes15. More importantly, this type of dissection
accounts for between 10 to 25 percent of all ischaemic strokes
in young and middle-aged patients16.
Types of Vertebral Artery Injury
The signs and symptoms produced by VBS are primarily
caused by brainstem ischaemia. The mechanism involved is
due to either mechanical and/or reflex constriction of the VA
at the site of injury, or from emboli travelling from the injury
site which then occlude the smaller arterial branches.
Mechanical restriction can occur when damage to the intima
of the vessel precipitates subintimal haematoma formation,
which may then result in occlusion of the vessel. A subintimal
haematoma may also result in a dissecting aneurysm and lead
to inadequate hind-brain perfusion17.
Arterial wall trauma can also produce arterial vasospasm,
which, combined with the presence of a haematoma, can
significantly affect VA blood flow. However, vasospasm by
itself can produce ischaemic brainstem symptoms or may
result in haematoma formation and in turn a dissecting
aneurysm18. Once a haematoma or thrombus has formed it is
then possible for emboli to break off and travel to the
brainstem or cerebellum, leading to infarction.
It has been hypothesised that minor trauma to the VA from
SMT may initially cause some minor vasospasm, which then
results in clot formation without apparent neurological signs
or symptoms2,19. On subsequent SMT procedures, emboli
may be dislodged by neck position or the thrusting
manipulation, thus resulting in brainstem or cerebellar signs
The time interval between the onset of VBS symptoms and
the SMT procedure may reflect the type of injury. Sudden
and severe neck pain immediately after SMT may indicate
VA trauma, while the onset of ischaemic symptoms soon after
SMT could indicate either VA vasospasm or the dislodgment
of emboli from a pre-existing thrombus and subsequent
In a review of 198 cases, 69% of symptoms occurred either
immediately or within minutes of the SMT, 18% within one
to six hours, 5% between seven and 24 hours and 8% 24
hours or longer after SMT2.
It may not be possible with even the most careful patient
history and physical examination to identify those patients at
risk of VBS. However, a careful history may alert the astute
practitioner to at least some people who may at higher risk of
VBS, or to those individuals who may already be experiencing
VA or carotid pathology and are therefore more likely to suffer
an SMT related stroke.
The history should include questions related to known risk
factors such as smoking, oral contraceptives, migraine
headaches, connective tissue diseases and a family history of
stroke and cardiovascular diseases, including past vascular
surgery. The patient should also be questioned of any recent
Table 2. Anatomical sections of the vertebral artery.
Section 1 That part of the artery from its origin to its entry into the transverse foramen at
Section 2 The part of the artery as it ascends the transverse foramina from C6 to C2
Section 3 That part of the artery where it leaves C2 and travels upward and laterally to
reach the foramina of the atlas transverse process
Section 4 Begins at the level of the foramen magnum and ends at the lower border of the
pons, where it joins with the opposite VA to form the basilar artery
history of episodes of dizziness, unsteadiness, vertigo or light-
headedness, visual disturbance, nausea, vomiting, headache,
paraesthesia or numbness, dysarthria, loss of taste, dysphagia
Dizziness is usually the most prominent symptom of
vertebrobasilar insufficiency and may not be accompanied
by any other signs or symptoms. Sudden and severe pain to
the side of the head and or neck and or occipital pain, may
also herald arterial trauma and possibly arterial dissection2,20.
With VA dissection, pain in the back of the neck develops in
half of patients, while in two thirds, headache occurs almost
always in the occipital region21. The median interval between
the onset of neck pain and the appearance of other symptoms
is two weeks, whereas other symptoms occur only 15 hours
after the onset of headache22. Carotid artery dissection should
also be considered in patients presenting with anterolateral
neck pain, unilateral facial or orbital pain and/or a unilateral
fronto-temporal headache18. Further, practitioners should be
aware of any patient presenting with neck pain that is either
not improved, or is aggravated, by movement of the neck.
This may indicate a vertebral or carotid artery dissection or
some other ‘red flag’ condition.
The dilemma faced by chiropractors and osteopaths is that
some of the symptoms of a dissecting VA, such as dizziness,
neck pain and occipital headache, can mimic common
musculoskeletal syndromes. The practitioner may assume
that these symptoms are attributed to the minor mechanical
strain, but the trauma may have actually precipitated a small
VBS2,20. Cervical SMT of such a patient may result in a
To some degree the physical examination is dependent on
the presenting complaint, signs and symptoms. In addition
to a standard physical examination protocol, it has been
suggested by various authors that blood pressure
measurement, neck auscultation and functional vascular tests
be performed to detect those patients at risk of VBS2. In one
study, hypertension had been noted in 53% of patients
presenting with spontaneous VA dissections23.
Neck auscultation appears of limited value for detecting VA
bruits, but may be of some benefit in detecting stenotic lesions
of the carotid arteries24.
Without doubt, the greatest emphasis in risk management of
VBS has been on the use of various functional vascular
screening tests in order to detect symptoms of cerebral
ischaemia. However, in his recent review, Terrett2 concludes
that none of these procedures have good predictive value of
an increased risk of VBS and should be abandoned for clinical
and medico-legal purposes.
Notwithstanding their poor predictive value, the COCA Risk
Management Subcommittee recommended that, prior to
cervical SMT, all patients should undergo blood pressure
testing, and in keeping with other similar guidelines for
cervical SMT25,26, at least one functional vascular test prior
to manipulation. Where the patient presents with anterior
neck pain or other symptoms possibly related to carotid artery
disease, neck auscultation should also be performed.
Although these tests may not reliably detect those patients at
risk of impending arterial injury and subsequent VBS, they
may detect pre-existing VA or carotid artery pathology, or
anomalous cerebral circulation14.
The Figure outlines the recommended history and
examination procedure to conduct on a patient presenting
with neck pain. These examinations should be performed on
any new patient, or an existing patient with new symptoms
whom, in the opinion of the practitioner, requires cervical
spine SMT. For all subsequent visits, where cervical SMT is
indicated, at the very least, a functional vascular test should
be performed prior to SMT being administered.
The recommended pre-SMT functional vascular test is usually
known as Maigne’s test27. This involves holding the patient’s
head for between 10 and 20 seconds in a position of rotation
and extension. The patient is then asked to report any
development of ischaemic symptoms such as dizziness,
nausea, numbness, paraesthesia etc, while the practitioner
observes for nystagmus. If ischaemic signs become apparent,
the patient’s head should be immediately brought back to the
It must be remembered that functional vascular testing is not
without its own dangers and in patients who present with
dizziness, vertigo or disequilibrium of unknown aetiology,
or those who have a history of previous ischaemic episodes;
this test should not be performed.
In both instances, where Maigne’s test produces VBS
symptoms or there are pre-existing VBS symptoms of
unknown aetiology, SMT should be avoided until the cause
is known. Further, the absence of ischaemic signs and
symptoms on testing does not in anyway guarantee the
practitioner that it is safe to proceed with manipulation14.
Volume 11 • Number 1 • March 2003 | ACO
As there is no reliable and valid method of detecting those
patients who are vulnerable to VBS, it is recommended that
all patients be made fully aware of the rare but serious
complications associated with cervical spine SMT. The use
of a clearly written Informed Consent should clearly outline
the risks and state what consequences may occur after cervical
Signs and Symptoms of
Vertebrobasilar Insufficiency and
Vertebral Artery Trauma
Any practitioner who employs therapeutic manipulation for
the cervical spine should be fully aware of the signs and
symptoms of post-manipulative VBS, vertebrobasilar
ischaemia (VBI) or VA damage. Terrett29 succinctly
summarises these symptoms with the 5D’s And the 3N’s:
Drop attacks/loss of consciousness
Diplopia (or other visual disturbances)
Dysarthria (speech difficulties)
Ataxia of gait, walking difficulties or incoordination
of the extremities, falling to one side
Nausea and/or vomiting
Numbness to one side of the face and/or body
In addition, severe and sudden head and/or neck pain after
SMT, with or without neurological symptoms, may indicate
vertebral or carotid artery damage.
Patient Management after SMT
related VBI S ymptoms
If any symptoms relating to VBI or VA damage occur,
immediately return the patient’s head to the neutral position
and cease any further treatment. Under no circumstances
should the neck be re-manipulated as this may cause further
VA damage. Observe the patient and if symptoms do not
resolve immediately, or they progress, arrangements should
be made to transport the patient to the nearest hospital
emergency department by ambulance. Both the paramedics
and the emergency department should be advised as to the
sequence of events and development of symptoms and what
may be the possible cause. The patient should be comforted
and without admitting guilt, the practitioner should be
sympathetic to their needs. If the patient has to be transferred
to hospital, the patient’s nearest of kin should be advised.
Figure. Recommended approach to the patient with neck pain.
Anterior neck pain?
Mechanical neck pain?
Standard physical examination
Blood pressure testing
Maigne’s test (or equivalent)
- risk factors
- dizziness, unsteadiness,
vertigo or light-headedness
- visual disturbance
- nausea, vomiting
- paraesthesia or numbness
- dysarthria; loss of taste
- dysphagia; hiccups
The most common symptom of VBI is dizziness, which may
not be accompanied by any other signs or symptoms. The
problem for the practitioner is that there are many causes of
dizziness and one such cause, cervicogenic vertigo, may be
induced by the neck position during Maigne’s test and may
also respond to SMT. However, unless the practitioner is
absolutely sure that these symptoms are not due to VBI, the
suggested protocol should be followed.
If the symptoms resolve after resting the patient, the patient
should still not be re-manipulated, but be reassessed and
examined for possible referral to their general practitioner
for further diagnostic testing or specialist neurological
assessment. On future visits and after assessment by their
GP or specialist, it is recommended that only low force (non-
manipulative) techniques be employed until the practitioner
is sure that the symptoms were not related to VBS. It is also
important to remember that in many cases VBS and stroke
like symptoms occur only after several previous uneventful
manipulations to the cervical spine4. Therefore, any sign or
symptom of VBI or VA trauma should be regarded as such
until proved otherwise.
Given the appropriate emergency medical care, the prognosis
for victims of VBS is very good with up to 75% of patients
making a full or good functional recovery.
The use of this protocol in no way guarantees the prevention
of SMT associated VBS but it is hoped that adherence to
these guidelines will diminish the risk. Regardless of how
careful a practitioner is, without adequate record keeping and
clinical notes, and appropriate informed consent, most claims
are indefensible in a court of law.
Summary of Important Points
! Risk factors for SMT associated VBS may include:
Previous history of ischaemic symptoms, such as
dizziness from head movements
Anomalous cerebral circulation
Diseases of the vessels
Connective tissue diseases
! Manipulation of the cervical spine should not be
performed with techniques that employ greater than 45°
of rotation, with or without neck extension.
! A thorough patient history is essential and should include
questions relating to:
Known risk factors
Dizziness, unsteadiness, light-headedness etc.
Sudden and severe neck/head pain.
! A thorough physical examination should be performed
on all new patients, or existing patients with new
symptoms whom, in the opinion of the practitioner,
requires cervical SMT. This physical examination should
Blood pressure testing;
Neck auscultation (in the presence of anterior neck
Maigne’s test on all patients prior to every cervical
! Every new patient who may require cervical spine
manipulation should be fully informed of the attendant
risks by the use of a clearly written Informed Consent
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