[Early and middle latency auditory evoked potentials in vertebrobasilar strokes]

Brainstem auditory evoked potentials (BAEPs) and middle-latency auditory evoked potentials (MLAEPs) have been recorded in 67 patients who had a stroke in well-defined territories of the vertebral and basilar arteries. Either CT scan or MRI have been performed in all cases. BAEPs were abnormal in 41/67 patients and MLAEPs were abnormal in 25/39 patients. BAEPs abnormalities were either bilateral (29/41 cases) or unilateral (12/41 cases). All components of BAEPS were unilaterally absent in four cases and bilaterally in one case. Pa component of MLAEPs was unilaterally delayed or reduced in five cases and bilaterally in 20 cases. Considering the topography of the infarct as shown by CT scan or MRI: medulla oblongata (13 cases): BAEPSs were normal in nine cases; pons (24 cases): BAEPs were abnormal in 16 cases; MLAEPs were abnormal in ten of 15 patients whose BAEPs were abnormal as well; mesencephalon (seven cases): BAEPs were abnormal in only two cases, and MLAEPs were abnormal in two cases one of which BAEPs were normal; in patients with diffuse infarctions either BAEPs or MLAEPs or both were abnormal in all cases. Stimulation of the ear ipsilateral to the lesion disclosed more BAEPs or MLAEPs abnormalities than stimulation of the contralateral ear.