Spinal manipulative therapy (SMT), especially hyperextension and rotation. have often been associated with cervical artery dissection (CAD), a tear in the internal carotid or the vertebral artery resulting in an intramural haematoma and/or an aneurysmal dilatation. But is the association causal? This question is often the subject of fierce discussions between chiropractors and the real doctors.
The lack of established causality relates to the chicken and egg discussion, i.e., whether the CAD symptoms lead the patient to seek cervical SMT or whether the cervical SMT provokes CAD along with the non-CAD presenting headache and/or neck complaint.
The aim of a new review was to provide an updated step-by-step risk-benefit assessment strategy regarding manual therapy and to provide tools for clinicians to exclude cervical artery dissection.
In light of the evidence provided, the reality, according to the review-authors, is:
- a) that there is no firm scientific basis for direct causality between cervical SMT and CAD;
- b) that the internal carotid artery (ICA) moves freely within the cervical pathway, while 74% of cervical SMTs are conducted in the lower cervical spine where the vertebral artery (VA) also moves freely;
- c) that active daily life consists of multiple cervical movements including rotations that do not trigger CAD, as is true for a range of physical activities;
- d) that a cervical manipulation and/or grade C cervical mobilization goes beyond the physiological limit but remains within the anatomical range, which theoretically means that the artery should not exceed failure strain.
These factors underscore the fact that no serious adverse event (AE) was reported in a large prospective national survey conducted in the UK that assessed all AEs in 28,807 chiropractic treatment consultations, which included 50,276 cervical spine manipulations.
The figure outlines a risk-benefit assessment strategy that should provide additional knowledge and improve the vigilance of all clinicians to enable them to exclude CAD, refer patients with suspected CAD to appropriate care, and consequently prevent CAD from progressing.
It has been argued that most patients present with at least two physical symptoms. The clinical characteristics and recommendations in the figure follow this assumption. This figure is intended to function as a knowledge base that should be implemented in preliminary screening and be part of good clinical practice. This knowledge base will likely contribute to sharpening the attention of the clinicians and alert them as to whether the presenting complaint, combined with a collection of warning signs listed in the figure, deviates from what he or she considers to be a usual musculoskeletal presentation.
Even though this is a seemingly thoughtful analysis, I think it omits at least two important points:
- The large prospective UK survey which included 50,276 cervical spine manipulations might be less convincing that it seems. It recorded about one order of magnitude less minor adverse effects of spinal manipulation than a multitude of previously published prospective surveys. The self-selected, relatively small group of participating chiropractors (32% of the total sample) were both experienced (67% been in practice for 5 or more years) and may not always have adhered to the protocol of the survey. Thus they may have employed their experience to intuitively select low-risk patients rather than including all consecutive cases, as the protocol prescribed. This hypothesis would ﬁrstly account for the unusually low rate of minor adverse effects, and secondly, it would explain why no serious complications occurred at all. Given that about 700 such complications are on record, the low incidence of serious adverse events could well be a gross underestimate.
- The effect of chiropractic spinal manipulative therapy is probably due to a placebo response. This means that it should probably not be done in the first place.