Hemifacial spasm: intraoperative electromyographic monitoring as a guide for microvascular decompression

Microvascular decompression is the logical and well-accepted treatment of choice for hemifacial spasm (HFS). In experienced hands, good to excellent results can be obtained. However, sometimes the exact site of the vascular compression is unclear. The aim of this study was to analyze whether intraoperative monitoring by stimulated electromyography of the facial nerve may help to improve the results of vascular decompression for HFS. In a series of 74 patients operated for HFS, the impact of intraoperative facial nerve monitoring on the surgical procedure was analyzed by use of the clinical and operative patient records. The role of this type of monitoring, with assessment of the so-called abnormal muscle response, was broken down into four categories: a guiding, a confirming, an indirect confirming, or an inconclusive role. The relationship between abnormal muscle response monitoring results and final surgical outcome was analyzed. The overall cure rate was 87.8%, including patients who had previously undergone unsuccessful operations. Complications were minor, and hearing impairment was found in 2.7% of patients. A guiding role of intraoperative monitoring was apparent in 33.8% of patients, and a confirming role was demonstrated in 52.7% of patients, which resulted in a positive contribution of approximately 87% for intraoperative facial monitoring in microvascular decompression for HFS. In patients defined as guiding cases, the cure rate was 92%. This study demonstrates the applicability and usefulness of intraoperative facial nerve monitoring in microvascular decompression operations for HFS.