Intraoperative monitoring of facial aberrant responses during microvascular decompression for hemifacial spasm

Objective To explore the importance of intraoperative aberrant responses monitoring as a guide for microvascular decompression. Method 40 patients of hemifacial spasm underwent intraoperative monitoring of facial aberrant responses during microvascular decompression. Of 40 patients, 23 were female and 17 were male. The age ranged from 32 to 68 years with a mean of 49.8 years. No muscle relaxants were used except for induction of anesthesia. The aberrant responses recorded from the mentalis muscle during stimulation of the temporal branch of the facial nerve. Result Before open the dura mater, 39 out of 40 cases showed aberrant responses with a latency of about 10 msec after stimulation. These responses disappeared in 38 patients at the end of operation. In 11 patients, the abnormal responses disappeared prior to decompression of the nerve, in 22 patients, these response disappeared after interposition of the Telfon between the vessel and the brain stem. In 6 patients, the response did not disappear after decompression of the nerve, multiple vascular compressions occur in 3 cases, in other 3 cases, the Telfon contacted to the facial nerve. In 6 patients, after decompression, no cerebellar retraction, the abnormal responses were reappearance, and disappeared after afresh exploration. Following time is 5.2-6.3 years, means is 5.7 years. The complete recovery rate was 94.7%, Recurrence rate 2.6%, inefficacy 2.6%. Conclusion This study demonstrates that intraoperative facial aberrant response recordings are useful to identify the compressing vessel that causes the spasm and to ensure that complete decompression of the nerve has been accomplished.