To investigate the therapeutic effects of different hearing protection strategies in microvascular decompression for hemifacial spasm (HFS-MVD).

A randomized controlled trial was designed to include 360 patients with HFS-MVD under the monitoring of brainstem auditory evoked potentials (BAEPs) in Neurosurgery Department of China-Japan Friendship Hospital from December 2015 to October 2018. Before surgery, random digital table method was performed and patients were divided into "simple waiting group" , "warm saline perfusion group" and "Nimodipine perfusion group" , 120 cases in each group. When the hearing loss alarm occurs in BAEPs during the operation (the latency of Ⅰ-Ⅴ wave delayed more than 1ms or the amplitude of wave V decreases more than 50%), the intervention was performed according to the preoperative grouping. The changes of BAEPs during the operation were divided into four types: stable maintenance type Ⅰ (no alarm, no intervention), stable recovery type Ⅱ, partial damage type Ⅲ, and complete damage type Ⅳ. All patients underwent postoperative hearing examinations (pure tone audiometry and speech discrimination score) to confirm the hearing loss.

The intervention measures were implemented in 146 patients in this group, including 47 patients in simple waiting group, 50 patients in warm saline perfusion group and 49 patients in Nimodipine perfusion group. The difference of composition of Ⅱ, Ⅲ, Ⅳ for total interventions among three groups was considered statistically significant (P<0.05). The difference of type and composition ratio between the simple waiting group and the warm saline perfusion group was considered statistically significant (χ²=8.754, P=0.013). The difference of Nimodipine perfusion group and simple waiting group or warm saline perfusion group was no significant difference (χ²=6.119, 0.247; P=0.047, 0.884). There was no significant difference of postoperative hearing function to the total number of interventions among three groups (P>0.05).

When hearing damage occurs by combined electrophysiological monitoring during MVD operation, immediately suspending the operation and using warm normal saline to backfill the operation area, which re-establishes the cerebrospinal fluid environment, is a simple and relatively effective rescue method.