BASILAR ARTERY BLOOD-FLOW DURING HEAD ROTATION IN VERTEBROBASILAR ISCHEMIA

Patients and methods - Forty-six patients with vertebrobasilar ischemi a and 40 control subjects were examined during head rotation using tra nscranial Doppler ultrasonography. Results - In the control group, no difference in blood now velocity through tile BA was found between the neutral and rotated positions. Based on these data, a blood low reduc tion in the BA of more than 20% was considered to be significantly abn ormal (p<0.01). In three of 46 patients no signal was detectable in th e BA using TCD. The reduction in blood flow Velocity through the BA du ring head rotation was strongly dependent on the condition of the VA; none of 23 patients without atherosclerotic lesions or hypoplasia oi t he VA developed a significant reduction in blood flow through the BA. Two of 11 patients with unilateral VPI lesions had significantly reduc ed blood now in the BA (27% and 31%), although both were asymptomatic. Five of nine patients with bilateral VA lesions showed a significant reduction in blood flow through the BA (mean=52%, minimum=30%), and fo ur of these developed clinical symptoms such as vertigo or diplopia du ring tile relation maneuver. Conclusion - These data suggest that pati ents with uni- or bilateral lesions of the VA are at risk for developi ng clinically relevant reductions in blood Bow through the BA during h ead rotation. Because not all patients with VA lesions developed reduc ed blood flow velocity, we conclude that individual vascular mechanism s must play an important compensatory role.