Vertebral artery dominance, brainstem auditory evoked potential, and vertigo of vascular origin

Objective: Vertebral artery dominance (VAD) is defined when there is a significant difference between the diameters of the vertebral arteries (VAs). VAD may be a risk factor for vertigo of vascular origin. The objectives of this study were: (1) to investigate changes of brainstem auditory evoked potential (BAEP) in patients with vertigo caused by VAD through magnetic resonance; and (2) to understand the possible mechanism(s) by which VAD triggers vertigo of vascular origin. Methods: This prospective study involved 64 patients with vertigo, including 35 patients with VAD (VAD group) and 29 without VAD (non-VAD group) as detected by head magnetic resonance angiography. Age, sex, and other clinical histories were comparable in both groups. The degree of vertigo was graded and BAEP examination was performed in each patient. BAEP changes as well as their correlations of BAEP with the dominant VA and basilar artery (BA) were analyzed in both groups. Results: The rate of abnormal BA shapes was 60% in the VAD group compared with 34.5% in the non-VAD group (Chi-square = 4.135, P<0.05). The median BA curvature was higher in the VAD group than that in the non-VAD group, 3.67 and 1.73 mm, respectively (P<0.01). Peak latencies (I, III, and V) in the VAD group were longer than those in the non-VAD group (P<0.01), but the difference in the III did not reach statistical significance (t=1.916, P>0.05). Interpeak latencies (III-V and I-V) were longer in the VAD group than those in the non-VAD group (P<0.05); there was no significant difference in the interpeak latencies of I-III (P>0.05). The III-V/I-III ratios were higher in the VAD group than those in the non-VAD group. The vertigo severity level was significantly higher in the VAD group than that in the non-VAD group (3.2 +/- 1.0 versus 2.2 +/- 0.7). The vertigo severity level correlated with VAD and every major anomaly index of BAEP; its correlations with III-V/I-III were remarkably significant (r=0.617, P=0.013). Conclusion: The incidence of abnormal BA shapes and abnormal BAEP, and the vertigo severity level were higher in VAD patients. Moreover, VAD was found to correlate with abnormal BAEP, suggesting that VAD contributed to vertigo of vascular origin.