Clinical study of vestibular-evoked myogenic potentials and auditory brainstem responses in patients with brainstem lesions.

A total of 13 patients, who were diagnosed with localized brainstem lesions using MRI, were investigated. The diagnoses were multiple sclerosis in five patients, brainstem hemorrhage in three patients, pontomedullary infarction in one patient and Wallenberg's syndrome in four patients. In addition, 42 ears of 21 normal adult volunteers were also examined. In a patient with upper brainstem lesions mainly affecting the midbrain, the auditory brainstem response (ABR) was abnormal but the vestibular-evoked myogenic potential (VEMP) was normal. In four patients with middle brainstem lesions which mainly affected the pons, both ABR and VEMP were abnormal. In five patients with lower brainstem lesions which mainly affected the medulla, the ABR was normal but the VEMP was abnormal. In those patients with middle-to-lower brainstem lesions, a disappearance of VEMP reactions, delay of the positive-negative (PN) wave, increase in PN interpeak latency and decrease in PN amplitude on the affected side were confirmed. In conclusion, the VEMP test comprises a useful new diagnostic method for identifying lower brainstem lesions.