Acoustic evoked potentials characteristics in patients with vertebral artery hypoplasia and posterior circulation stroke

Abstract

Background/Aim. Acoustic evoked potentials (AEPs) represent an electrophysiological method used in diagnosing pathological changes of the brain stem (BSt), the acoustic nerve (its peripheral and central part), in patients in coma, in the confirmation of cerebral death, etc. The response includes seven negative waves which are generated in the structures of the BSt vascularized by the arteries of the posterior circulation. However, in everyday practice, due to their constancy, the first five waves are followed. The vertebral artery hypoplasia (VAH) is assumed to affect the AEPs finding. The current definition of VAH includes the criterion that the diameter of the blood vessel is ≤ 2 mm and that the ratio of the diameter of the left and right vertebral artery is ≥ 1 : 1.7. VAH is found in 5.3% of cases of the total population and its presence increases the risk of posterior circulation stroke (PCS). The aim of this study was to show a higher frequency of pathological findings of AEPs in patients with VAH and PCS and demonstrate the characteristics of AEP in that group of patients. Methods. This prospective study included 163 patients diagnosed with PCS over a period of two years. Computed tomography (CT) and magnetic resonance (MR) imaging (MRI) established the diagnosis of PCS. Suspicion of VAH was found by Color Doppler ultrasonography and confirmed by CT and MR angiography. All patients underwent AEPs testing. Wave amplitudes and interwave latencies (IWL) were monitored. Results. There was no statistically significant difference between gender (χ2 = 1.823; p = 0.176) and age in relation to VAH (p = 0.815). A statistically significant greater number of patients with multiple PCS had a positive VAH finding (VAH group, 42.3%) compared to those without VAH (noVAH group, 26.6%) (χ2=4.278; p=0.038). A statistically significant greater number of pathological AEPs was found in the group of patients with PCS and VAH (χ2 = 4.899; p = 0.026). A statistically significant IWL change accompanied by low amplitude waves in the VAH group has been determined (χ2 = 4.465; p = 0.034). Conclusion. The distribution of VAH is not gender- or age-related. The frequency of pathological AEPs findings (presence of associated changes in wave amplitudes and prolonged IWL) is statistically significantly higher in patients with VAH and PCS.

Keywords

• brain stem infarctions
• electrophysiology
• evoked potentials
• auditory
• brain stem
• vertebrobasilar insufficiency