More Evidence for SMT and Vertebral Artery Dissection
By Simon French

The May 2003 edition of Neurology¹ has published a case-control study examining whether spinal manipulative therapy (SMT) is a risk factor for vertebral artery dissection.

Patient records were reviewed from two academic stroke centres in the United States. Cases (n = 51) consisted of patients under the age of 60 who suffered from cervical artery dissection. Controls (n = 100) were patients from the same hospitals who had suffered from other causes of stroke, matched by age and sex. The patients were then contacted for further information regarding their activity prior to their stroke.

Patients with dissection were slightly younger than the controls. Seven patients with dissection had SMT within 30 days compared to three control patients. The dissection patients had an average of 1.4 days from SMT to stroke, compared to 8.4 days for the control patients. Overall, patients with vertebral artery dissection were six times more likely to have had SMT within 30 days.

The study has a number of weaknesses, including confounding due to age, selection bias and recall bias. Age is a possible confounder in that younger patients are more likely to visit a chiropractor and suffer from a dissection than older people. It is therefore possible that the age difference between the groups is responsible for the results rather than the SMT. Patients with dissection who had undergone SMT may have been more likely to participate if they were motivated to disclose the perceived cause of their stroke. Patients were required to recall the events surrounding the time of the stroke, and patients who had a dissection and had SMT may be influenced in their recollection of these events. The records of the practitioner who performed the SMT were not reviewed as part of the study to verify the clinical history or the type of manipulation that was performed.

Practitioners who perform cervical manipulation cannot ignore the increasing body of evidence surrounding SMT and vertebral artery dissection. Also, there is no definitive evidence that cervical manipulation is more effective than other manual therapy procedures for neck pain. The diligent practitioner must continue to perform risk management strategies including obtaining informed consent.

1. Smith WS, Johnston SC, Skalabrin EJ, et al. Spinal manipulative therapy is an independent risk factor for vertebral artery dissection. Neurology 2003;60:1424–1428.