TRANSIENT RETROCOCHLEAR LOW-FREQUENCY SENSORINEURAL HEARING-LOSS - A NEW CLINICAL ENTITY

Sensorineural hearing loss (SNHL) of varying types and extent developed in a number of the 963 patients who underwent microvascular decompression for hemifacial spasm. Fourteen of the patients with hearing loss had transient low-frequency SNHL. Low-frequency SNHL is seldom noted in patients with retrocochlear hearing loss, but five of these patients had Horner's syndrome or bulbar palsy. The results of Bekesy audiometry, auditory brainstem response, and electrocochleography in the patients were also suggestive of brainstem pathology. Surgical records revealed that all of them had excessively short perforating arteries surrounding the entry zone of nerves VII and VIII, so that they had to be stretched during surgery. Occlusion of perforating arteries is suspected to have caused lateral brainstem infarction around the entry zone of nerves VII and VIII, and resulted in low-frequency SNHL.