I have repeatedly discussed the risks of chiropractic manipulation. Sadly, when doing so, we have to rely mostly on case reports (there is no monitoring system that would record such events, reliable incidence figures are therefore not available). This means every new case report is of considerable importance.
Korean neurosurgeons recently reported the case of a patient who had an infarction of the posterior inferior cerebellar artery (PICA) after a chiropractic cervical manipulation. A 39-year-old man visited the emergency room with signs of cerebellar dysfunction, presenting with a 6-hour history of vertigo and imbalance. Two weeks before, he had been treated by a chiropractor for intermittent neck pain. At the time of admission, brain computed tomography, magnetic resonance imaging, and angiography revealed an acute infarction in the left PICA territory and occlusion of the extracranial vertebral artery (VA; V1/2 junction) as a result of a dissection of the VA. Angiography revealed complete occlusion of the left PICA and arterial dissection was shown in the extracranial portion of the VA. The patient was treated with antiplatelet therapy. Three weeks later, he was discharged without any sequelae.
The authors concluded that the possibility of VA dissection should be considered at least once in patients presenting with cerebellar dysfunctions with a recent history of chiropractic cervical manipulation.
In the discussion section, the authors leave little doubt about the question of causality: damage to the V3 portion is the most common injury that may occur after chiropractic manipulation related to anatomical structures. The VA is located horizontally in a groove in the upper side of the atlas’ posterior arch. During abruptly forced neck rotation and stretching, the gap between the atlas and the atlanto-occipital membrane, which the VA penetrates, can be stretched, resulting in dissection. In our case, it appeared that the V1/2 junction had been dissected due to excessive lateral bending of the neck, thought to be caused by an impact to the left transverse foramen of the sixth cervical spine, through which the left VA passes. It is presumed that there was a mechanical injury to the vessel wall at the time of the procedure, which caused dissection and then the thrombus generated, and two weeks after small emboli caused the occlusion of PICA. Low-speed, high-amplitude manipulations that consist of a series of smooth, repetitive movements are configured in certain areas of the neck, and this does not often cause damage. However, a sudden thrust or high-speed, low-amplitude manipulation is often considered the cause of VA dissection. In particular, this type of manipulation can be theorized to result in a sudden, symmetrical rotation of the extended cervical vertebrae, leading to damage to the high cervical and proximal parts of the carotid artery and VA.
It is high time, I think, that chiropractors take such events seriously. At the very minimum, we need a system of monitoring such cases, so that – eventually – we will be able to define their frequency. In this context, it is obviously important to remember that there is precious little evidence to suggest that neck manipulations are effective for any condition. What inescapably follows is clear: until we have reliable incidence data, it is wise to avoid chiropractic neck manipulations altogether.