INTRAOPERATIVE MONITORING BY FACIAL ELECTROMYOGRAPHIC RESPONSES DURING MICROVASCULAR DECOMPRESSIVE SURGERY FOR HEMIFACIAL SPASM

The facial electromyographic response was monitored intraoperatively i n 40 patients with hemifacial spasm who were operated on by microvascu lar decompression of the facial nerve. All 40 patients showed an abnor mal facial electromyographic response (lateral spread response) with a latency of about 10 msec after stimulation. The abnormal response res olved before decompression in 22, resolved immediately with decompress ion in 16, and failed to resolve in two. Of the 38 patients in whom th e abnormal response disappeared during surgery, 36 were postoperativel y free from hemifacial spasm and two had mild hemifacial spasm. The tw o patients in whom the lateral spread response did not disappear durin g surgery showed persistent hemifacial spasm. In conclusion. Disappear ance of the lateral spread response during surgery correlated with the absence of hemifacial spasm in the early postoperative period. The pr ognosis of hemifacial spasm was good in cases in whom the lateral spre ad response disappeared. Therefore, the authors think that intra-opera tive facial electromyography is very useful in assessing the efficacy of microvascular decompression and in predicting the prognosis of hemi facial spasm.