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

OBJECTIVE: Microvascular decompression is the logical and well-accepted tre atment 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 whet her intraoperative monitoring by stimulated electromyography of the facial nerve may help to improve the results of vascular decompression for HFS. METHODS: In a series of 74 patients operated for HFS, the impact of intraop erative facial nerve monitoring on the surgical procedure was analyzed by u se 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 conf irming, or an inconclusive role. The relationship between abnormal muscle r esponse monitoring results and final surgical outcome was analyzed. RESULTS: The overall cure rate was 87.8%, including patients who had previo usly undergone unsuccessful operations. Complications were minor, and heari ng impairment was found in 2.7% of patients. A guiding role of intraoperati ve monitoring was apparent in 33.8% of patients, and a confirming role was demonstrated in 52.7% of patients, which resulted in a positive contributio n of approximately 87% for intraoperative facial monitoring in microvascula r decompression for HFS. In patients defined as guiding cases, the cure rat e was 92%. CONCLUSION: This study demonstrates the applicability and usefulness of int raoperative facial nerve monitoring in microvascular decompression operatio ns for HFS.