Spontaneous Cervical Artery Dissections and Implications for Homocysteine

Dr Rosner's interesting commentary1 raised some issues that warrant discussion.

Table 2 of the commentary,1 which outlined current vertebrobasilar artery risk assessment options, omitted mentioning that simple nonimaging Doppler ultrasound has value in assessing the patency of vertebral arteries (VAs)2 and internal carotid arteries (ICAs) and hence the adequacy of the collateral supply, which can influence the chance of stroke after cervical artery dissection (CAD).3 Doppler ultrasound can detect the hemodynamic changes associated with CAD4 and therefore may provide some indication, along with pain presentation, of a neurologically silent CAD.3 There is evidence that Doppler ultrasound velocimetry is useful in testing VAs for rotational stenosis, which seems to be an independent risk factor of vertebrobasilar stroke.2 The limitation to Doppler ultrasound that Dr Rosner1 listed actually referred to “manual compression and provocation testing,” and so, it is irrelevant.

Dr Rosner1 appeared to make the case that there is only 1 identifiable risk factor of postmanipulation stroke, ie, mild hyperhomocysteinemia, and that premanipulation screening should be focused on this 1 factor. It is interesting to note that, although the commentary relied heavily on the study by Pezzini et al,5 the authors of this study, and those of the accompanying editorial,6 it did not recommend screening for hyperhomocysteinemia. The editorial6 suggested that this factor may play a role in the pathogenesis of only some spontaneous CAD subtypes.

Pezzini et al5 found that almost 14% of the normal population had homocysteine levels higher than the cutoff point of 12.0 μmol/L for the study. What do chiropractors do when approximately 14% of their patients, who are normal, could test positive to this blood test? Should so many patients be denied neck manipulation unnecessarily? To suggest some modification of the manipulative technique would imply that mechanical factors need to be considered. If so, chiropractors and other spinal manipulators need to screen for mechanical effects, which they have direct input on, by virtue of the therapy that they administer.

Doppler velocimetry, which is painless, completely safe, and noninvasive, can be used to assess the patency and mechanical effects of neck movement on VAs and ICAs rapidly and inexpensively within a chiropractic clinic environment.2 Measuring homocysteine levels requires the patient to fast and have a blood sample taken via venipuncture the following morning at a clinical reference laboratory. This can present some logistical problems for patients and pose the risk of injury to the median nerves and the medial and lateral cutaneous nerves of the forearm (1/25,000 antecubital fossa venipunctures), as well as cross-infection of antibiotic-resistant bacteria.

Ideally, constitutional factors that can cause arterial fragility should be able to be tested by chiropractors in their clinics. There is evidence linking arterial wall elasticity with dissection,7 and studies indicate that Doppler velocimetry determination of pulse wave velocity can measure the elasticity of arteries.8 Therefore, the potential of Doppler velocimetry to be used in detecting arterial fragility of specific vessels such as VAs and ICAs needs to be explored.