Transient retrocochlear low-frequency sensorineural hearing loss: a new clinical entity

Area of Science:

• Neurosurgery
• Audiology
• Neurology

Background:

• Microvascular decompression is a surgical treatment for hemifacial spasm.
• Sensorineural hearing loss (SNHL) is a potential complication, though typically not low-frequency.
• Transient low-frequency SNHL is rarely reported in retrocochlear hearing loss cases.

Purpose of the Study:

• To investigate the occurrence and potential causes of sensorineural hearing loss (SNHL) following microvascular decompression for hemifacial spasm.
• To explore the association between surgical findings and the development of SNHL.

Main Methods:

• Retrospective analysis of 963 patients undergoing microvascular decompression for hemifacial spasm.
• Evaluation of audiological tests (Békésy audiometry, auditory brainstem response, electrocochleography) in patients with hearing loss.
• Review of surgical records focusing on vascular anatomy at the entry zone of cranial nerves VII and VIII.

Main Results:

• A subset of patients developed SNHL, with 14 experiencing transient low-frequency SNHL.
• Five patients with low-frequency SNHL also presented with Horner's syndrome or bulbar palsy.
• Surgical records indicated excessively short perforating arteries in all affected patients, requiring nerve stretching.

Conclusions:

• Occlusion of short perforating arteries during surgery is suspected to cause lateral brainstem infarction.
• This infarction may lead to the observed transient low-frequency SNHL.
• The findings suggest a link between specific vascular anomalies and SNHL after microvascular decompression.