We took great pains in our research letter not to claim that we were presenting an incidence study of arterial dissection, but rather we described the likelihood that a chiropractor would be made aware of such an occurrence. The statement that only cases that led to lawsuits were included is incorrect. Chiropractors are required to report all cases of neurological symptoms that may indicate a stroke following treatment. Of the 43 cases reviewed, only 22 actually filed a lawsuit.
We found that chiropractors were made aware of 23 cases of dissection following manipulation over a 10-year period in Canada, where approximately 30 million chiropractic visits occur each year. The case-control study by Rothwell and colleagues1 noted 6 cases of vertebral artery occlusion that could be attributed to chiropractic manipulation over a 6-year study period in Ontario, where 10 million chiropractic visits occur each year. This suggests that the number of cases brought to the attention of chiropractors was similar to that anticipated from the only case-control study in Canada.
A recent review of the literature, and multiple cases of stroke associated with manipulation, has shown that dissection can occur following any method of manipulation or any type of trivial neck movement or trauma and is not limited to those movements that have only rotation and extension.2,3 This observation led us to survey the total number of manipulations rather than specific types of manipulation.
Schievink and colleagues suggest up to 50% of strokes following manipulation occur in patients with neck pain caused by an unrecognized spontaneous dissection prior to chiropractic treatment.4 This explains how dissection can occur with any movement of the neck in a predisposed patient. To reduce the frequency of dissections associated with manipulation, the ability to diagnose a dissection prior to manipulating the cervical spine may be a fruitful area for further research.
Scott Haldeman Department of Neurology University of California Irvine, Calif. Paul Carey Canadian Chiropractic Protective Association Toronto, Ont.
References
- 1.Rothwell DM, Bondy SJ, Williams JI. Chiropractic manipulation and stroke. A population-based case-control study. Stroke 2001;32(5): 1054–60. [DOI] [PubMed]
- 2.Haldeman S, Kohlbeck FJ, McGregor MM. Stroke, cerebral artery dissection, and cervical spine manipulation therapy. J Neurology. In press. [DOI] [PubMed]
- 3.Haldeman S, Kohlbeck FJ, McGregor M. Risk factors and precipitating neck movements causing vertebrobasilar artery dissection after cervical trauma and spinal manipulation. Spine 1999; 24: 785–94. [DOI] [PubMed]
- 4.Schievink WI, Mokri B, Piepgras D, Parisi Gilbert P. Cervical artery dissections associated with chiropractic manipulation of the neck: the importance of pre-existing arterial disease and injury [abstract]. J Neurol 1996;243(Suppl 3):92S.