I agree with Moira Kapral and Susan Bondy that more research is needed concerning cervical manipulation and the risk of stroke.1 However, I strongly disagree with their view that the study by Rothwell and colleagues2 provides a “theoretically less biased estimate of the risk of stroke secondary to chiropractic manipulation” than the study by Haldmeman and colleagues.3 The paper by Rothwell and colleagues2 is a correlational study and in no way describes a causal relationship.
They reported that patients aged less than 45 years who were admitted to hospital with a vertebrobasilar accident were 5 times more likely to have visited a chiropractor within a week of the accident than controls and were 5 times more likely to have had 3 or more visits with a cervical diagnosis in the month before the accident than controls.
There are several potential confounding factors in this study. For example, chiropractors do not always perform spinal manipulation for patients with a cervical diagnosis; they may use one of the many other modalities available in chiropractic medicine (and in physical therapy, for that matter).
As a second example, a patient with a pre-existing vertebrobasilar compromise visits a chiropractor complaining of neck symptoms that are unrelated to that compromise, and manipulation treats these symptoms but does not affect the vertebrobasilar artery in any way.
As a third example, a patient sustains a vertebrobasilar artery injury from a motor vehicle accident and visits a chiropractor, who suspects vertebrobasilar compromise. An immediate referral is made to a neurologist, who misses the diagnosis of compromise. The patient dies in the parking lot outside the neurologist's office, having visited the chiropractor and the neurologist that week.
The relationship between stroke and visits to a neurologist or other medical provider should be studied; this relationship may well be stronger than that between stroke and visits to a chiropractor.
Gregory T. Wright Wright Chiropractic & Sports Injury Care West Harwich, Mass.
References
- 1.Kapral MK, Bondy SJ. Cervical manipulation and risk of stroke [editorial]. CMAJ 2001;165(7): 907-8. [PMC free article] [PubMed]
- 2.Rothwell DM, Bondy SJ, Williams JL. Chiropractic manipulation and stroke: a population-based case–control study. Stroke 2001;32:1054-60. [DOI] [PubMed]
- 3.Haldeman S, Carey P, Townsend M, Papdopoulos C. Arterial dissection following cervical manipulation: the chiropractic experience. CMAJ 2001; 165 (7):905-6. [PMC free article] [PubMed]