During the stretch of one year, about half of all adults would have felt some type of neck pain, and some of these will seek treatment. Many of these patients will receive spinal manipulation and most will probably feel some immediate relief.
Spinal manipulation can be described as a manual maneuver in which a spinal segment is placed in an extreme ‘end’ position. Upon which the manipulator adds a quick, low force and shallow movement, resulting in the spinal joint giving way in an ‘additional’ step, which is within its anatomical boundaries but usually outside the natural movement pattern. This is meant to affect the biomechanics and/or neurology of that spinal segment, which may or may not have a positive effect on spine-related symptoms.
Usually spinal manipulation is as uneventful (in a negative sense) as when you crack the knuckles in your fingers. Nevertheless, it may also happen, although exceedingly rarely, that real adverse events occur after spinal manipulation of the neck, such as damage to the wall of the artery that passes through the neck to the brain (arterial dissection), which may result in a stroke, with various potentially catastrophic symptoms following.
If it closes off the arterial system, serious and perhaps irreversible damage may occur within the brain.
If this stroke is caused by a clot and the clot is small or lodges itself in an area where there is additional blood-supply, the symptoms may be minor or short-lasting. But if it closes off the arterial system, serious and perhaps irreversible damage may occur within the brain. This is broadly called a cerebro-vascular accident (CVA). Specifically, in relation to spinal manipulation, we are mainly dealing with a vertebral artery dissection with either local symptoms from the surrounding tissues or symptoms further away (vertebrobasilar stroke).
Arterial dissections may occur after serious trauma, after quite mundane activities which involve prolonged or extreme neck positions, and possibly also spontaneously. Cervical spine manipulation is therefore only one among many potential causes.
As the CVA is a rare occurrence and, as CVAs associated with spinal manipulation are even scarcer, it is a very difficult phenomenon to study, meaning that mainly very large case-control studies are suitable.
The cause of a stroke?
As this type of injury can occur spontaneously or after activities involving certain neck positions, a major question rears its head at regular intervals, namely: “Is the CVA truly the result of the cervical manipulation or is it only ‘an accident waiting to happen?” This question is based on the notion that people with a (painful) cervical dissection are likely to seek care, and if manipulation is performed in such patients, a clot may dislodge itself to complete the pathology but – on the other hand – it may have happened already, completely on its own, regardless of the manipulation.
Is the CVA truly the result of the cervical manipulation or is it only ‘an accident waiting to happen?
Indeed, a previous study* by Cassidy et al showed that vertebro-basilar stroke was equally common in people who had consulted a medical practitioner as in those consulting a chiropractor. For most practitioners using spinal manipulation after this report, the question was answered; the stroke patient’s early symptoms made him consult and the full-blown stroke would follow, regardless of the treatment.
However, not everybody agrees. Some argue, for example, that cervical manipulation does not have enough benefits to justify this potential risk.
In the present issue of Chiropractic & Manual Therapies, two teams are debating that old question, this time based on the issue of misclassification of cases. One team (Paulus &Thaler) argues that the Cassidy case-control study is faulty, because vertebro-basilar stroke in general was not separated from stroke specifically caused by vertebral artery dissections, the presumed culprit in cervical spinal manipulation. According to Paulus & Thaler, this would potentially result in a dilution of ‘real’ manipulative-related strokes among all other causes of stroke that are much more common. They argue that the Cassidy-analyses therefore were polluted by this misclassification, whereas the other team (Murphy et al) vehemently disagrees.
Without an international collaboration involving prospective cases this seems an almost impossible task.
Not surprisingly, we have here the added dimension of professional political boundaries; the ‘no-to-manipulation’ and the ‘yes-to-manipulation’-teams, representing two different professional groups.
The final word is clearly not yet pronounced on this issue and both these two teams agree that research has to address various methodological challenges to obtain a trustable answer. Nevertheless, without an international collaboration involving prospective cases this seems an almost impossible task, particularly in view of the rarity of the condition; problems in capturing all cases (going from the reversible to the permanent injuries); the likely large anatomical and physiological variations between individuals; and the daunting task of obtaining relevant and precise descriptions of treatments from a multitude of practitioners.
In the meantime, practitioners and patients have to make a decision, similarly to judging risk in other walks of life, such as, should I take the plane or stay at home?
*The study by Cassidy et al is from a subscription journal and the full article may not be accessible to you.