Manual Therapy 2005 (May); 10 (2): 154158 ~ FULL TEXT
Haymo Thiel, George Rix
Anglo-European College of Chiropractic,
13-15 Parkwood Road,
Bournemouth BH5 2DF, UK.
The combined extended and rotated cervical spine position has been postulated to affect vertebral artery blood flow by primarily causing a narrowing of the vessel lumen, usually within the artery contralateral to the side of head rotation. The production of brainstem symptoms during the manoeuvre has generally been considered to be a positive test result. As a consequence, functional pre-manipulation testing of the cervical spine has been part of clinical screening undertaken by chiropractors and other manual practitioners to rule out the risk of possible injury to the vertebral artery. To date, these testing procedures are taught to students and carried out in daily clinical practice, despite the considerable controversy that exists about their validity.
This paper considers and discusses the usefulness of functional pre-manipulation testing for clinical scenarios, involving dissection, spasm or stenosis of the vertebral artery, and makes the following recommendations:
(1) Practitioners must assess the patient thoroughly, through careful history taking and physical examination, for the possibility of vertebral artery dissection. It is important to note that vertebral artery dissection (VAD) may present as pain only, and may not be associated with symptoms and signs of brainstem ischaemia.
(2) If there is a strong likelihood of VAD, provocative pre-manipulation tests should not be performed, and the patient must be referred appropriately.
(3) In the patient presenting with symptoms of brainstem ischaemia due to non-dissection stenotic vertebral artery pathologies, provocative testing is very unlikely to provide any useful additional diagnostic information.
(4) In the patient with unapparent vertebral artery pathology, where spinal manipulative therapy (SMT) is considered as the treatment of choice, provocative testing is very unlikely to provide any useful information in assessing the probability of manipulation induced vertebral artery injury.
From the FULL TEXT Article:
Functional pre-manipulation testing of the cervical
spine has been part of clinical screening undertaken by
practitioners of spinal manipulative therapy (SMT) for
many years, and various protocols have been adapted to
rule out the risk of possible injury to the vertebral artery
(Carey, 1995; Rivett, 1995; Grant, 1996; Barker et al.,
2000). Since first reported in the literature in 1927 by
DeKleyn and Nieuwenhuyse (DeKleyn and Nieuwenhuyse,
1927), the combined extended and rotated
cervical spine position has been postulated to affect
vertebral artery blood flow by primarily causing a
narrowing of the vessel lumen, usually within the artery
contralateral to the side of head rotation. The production
of brainstem symptoms during the manoeuvre has
generally been considered to be a positive test result. To
date, these testing procedures are continued to be taught
to students and carried out in daily clinical practice,
despite the considerable controversy that exists about
their validity (Kunnasmaa and Thiel, 1994; Thiel et al.,
1994; Cote et al., 1996; Rivett et al., 1998; Licht et al.,
2000; Westaway et al., 2003). This may be partially
based on the belief that performance of these screening
tests, and a negative result, could offer the practitioner
some form of medico-legal or clinical negligence
protection, or that these tests may afford, both the
practitioner and the patient, a lesser risk of postmanipulation
Clinical tests may have one or more of five functions
(Table 1). Provocative or functional vertebral artery
insufficiency tests are most commonly used for diagnostic
or screening purposes. This commentary focuses
on the role of functional vertebral artery insufficiency
testing as a pre-manipulation screening tool. Clinical
tests are used to perform a specific function for a specific
condition, or risk factors for that condition, in a specific
population (Lang and Secic, 1997). In this sense, the
provocative or functional vertebral artery insufficiency
tests are considered to be a screen for otherwise
unapparent vertebral artery pathology that may represent
a pre-manipulation risk, in a situation where SMT
of the cervical spine is considered to be the treatment of
choice. By unapparent we mean the absence of
historical or other clinical features suggestive of vessel
pathology such as dissection, and/or brainstem ischaemia
(Table 2). This scenario reflects the clinical situation
that practitioners of SMT most commonly face with
respect to pre-manipulation screening in their daily
In assessing the usefulness of a screening procedure, a
prerequisite must be to define the pre-symptomatic
condition that it is aimed at detecting. Although the
exact pathophysiological mechanisms underlying stroke
and SMT are still unclear, the most commonly accepted
one is that of vertebral artery dissection (Frisoni and
Anzola, 1991). If this dissection or other sequelae related
to vessel wall injury was to be due to a pre-symptomatic
congenital or acquired weakness of the vessel wall, it is
hard to see how positional tests, aimed at assessing the
haemodynamics of that still patent vessel, will afford
any useful clinical information regarding the possible
risk of injury. Furthermore, in this scenario, performing
these tests alone may possibly put the patient at a higher
risk due to the potential stretching forces exerted on an
already weakened vessel wall. While obviously not in
vivo, studies on human cadavers have shown that strain
values exerted onto the vertebral artery during a premanipulation
test are higher than those observed during
a typical cervical SMT procedure (Symons et al., 2002).
Although there are no documented cases of dissection
following pre-manipulation testing alone, the literature
cites many examples of non-manipulation positional
manoeuvres of the head and neck that have been
associated with cerebrovascular injury (Thiel, 1991;
Vessel spasm is another pathophysiological process
that has been hypothesised by some to lead to vertebral
artery occlusion following SMT (Easton and Sherman,
1977; Schmitt, 1991). This may occur with or without
arterial wall damage. Again, and for the same reason as
for dissection, it is hard to see how on biologically
plausible grounds, a positional pre-manipulation test
could assess for the possibility of an impending
vasospasm. In summary, the construct validity of the
tests with these pathologies in mind is poor.
A less commonly accepted link between SMT and
stroke is embolisation from a pre-existing thrombus
formation in the vertebral artery. In the absence of
endothelial injury, this pathological process is most
commonly associated with atherosclerosis. The atheroma
alone may result in an asymptomatic partial
stenosis of the arterial lumen. Hypothetically, the
addition of a test, which may further occlude the vessel,
could result in sufficient alteration in arterial flow
characteristics to produce ischaemic brainstem symptoms.
On the other hand, it is also conceivable that the
test may dislodge the embolus resulting in stroke.
Hypoplasia of the vertebral arteries (p2 mm) has
been considered another stenotic factor related to postmanipulation
stroke (Mann and Refshauge, 2001).
There is no evidence to suggest that a hypoplastic vessel
has a greater predisposition to dissection. However,
some reports suggest that in the event of vessel injury, a
contralateral hypoplastic artery may not be able to
provide sufficient collateral circulation to prevent
ischaemia and possible infarction (Henderson and
Cassidy, 1998; Mann and Refshauge, 2001).
So what is the usefulness of the provocative or
functional vertebral artery insufficiency tests in detecting
lumenal stenosis due to thrombus or hypoplasia? In
attempting to address this question only in vivo Doppler
ultrasound studies of vertebral artery flow in human
subjects have been reviewed. As mentioned previously, it
is generally assumed that pre-manipulation positional
manoeuvres measure the degree of lumenal patency, or
absence thereof, via the production of transient brain-stem ischaemic symptoms. In other words, the test is
believed to be an indirect measure of vertebral artery
haemodynamics. However, a review of the literature on
vertebral artery flow studies clearly shows conflicting
results with regard to the effects of sustained premanipulation
positional manoeuvres. Doppler studies
attempting to measure the volume, velocity, or resistance
to contralateral vertebral artery flow, have
inconsistently indicated either a decrease or disappearance
in some of these flow parameters (Stevens, 1984,
1991; Refshauge, 1994; Haynes 1995, 1996, 2000, 2002;
Licht et al., 1998; Rivett et al., 1999; Yi-Kai et al., 1999;
Mitchell, 2003), or an insignificant or no change at all
(Weingart and Bischoff, 1992; Thiel et al., 1994; Cote
et al., 1996; Lantz et al., 1996; Licht et al., 1999; Zaina
et al., 2003) when applying a variety of functional premanipulation
tests. Further, there have been reports of
patients who had either known vertebral artery hypoplasia
or complete lumenal occlusion on neck rotation
but did not experience any symptoms during the premanipulation
manoeuvres (Bolton et al., 1989; Rivett et
al., 1998; Westaway et al., 2003). Of particular interest
are the Doppler studies by Licht and his co-workers
which seem to indicate that flow velocity in the vertebral
artery is neither significantly affected shortly after SMT
of the neck in asymptomatic subjects (Licht, 1998), nor
in subjects who had tested positive on performing premanipulation
tests (Licht et al., 2000).
Even if one accepts that to an extent, the significant
disparity of the results of the various studies on
vertebral artery flow during functional pre-manipulation
testing, is dependent upon a variety of methodological
factors, the weight of the evidence seems to strongly
suggest that these screening tests lack the necessary
sensitivity in order to be valid and dependable predictors
of risk. As such, a negative test result cannot determine
the safety of cervical SMT. The lack of sensitivity of the
pre-manipulation tests as a valid screening procedure is
further supported by some of the findings of Haldeman
et al. in their review of 64 medicolegal cases of
cerebrovascular accidents associated with SMT of the
cervical spine (Haldeman et al., 2002). In 27 of the
cases, the practitioner had described the use of a
pre-manipulation provocative screening manoeuvre,
however, none of these patients had shown any adverse
responses to this screening test before the manipulation.
In view of these arguments, we would like to make the
following observations and recommendations:
1. Practitioners must assess the patient thoroughly, through careful history taking and physical examination,for the possibility of vertebral artery dissection. It is important to note that VAD may present as pain only, and may not be associated with symptoms and signs of brainstem ischaemia (Table 2).
2. If there is a strong likelihood of VAD, provocative pre-manipulation tests should not be performed, and the patient must be referred appropriately.
3. In the patient presenting with symptoms of brainstem ischaemia due to non-dissection stenotic vertebral artery pathologies, provocative testing is very unlikely to provide any useful additional diagnostic information.
4. In the patient with unapparent vertebral artery
pathology, where SMT is considered as the treatment
of choice, provocative testing is very unlikely to
provide any useful information in assessing the
probability of manipulation induced vertebral artery
5. Practitioners might well now consider whether
provocative testing provides any real benefit to any
of these patient populations.
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