New Technology: Compound Abnormal Muscle Response During Microvascular Decompression for Hemifacial Spasm

Objective: To discuss effect of intraoperative compound abnormal muscle response (AMR) in patients undergoing microvascular decompression (MVD) for hemifacial spasm (HFS). Methods: Eighty-six HFS patients were underwent single or compound AMR monitoring during MVD. Single AMR recording was from the frontal muscle by stimulation of the marginal mandibular branch. Compound AMR recordings were obtained from the orbicularis oris and mentalis muscles by electrical stimulation of the temporal branch of the facial nerve, and from the frontal and orbicularis oculi muscles by stimulation of the marginal mandibular branch. Clinical outcome was compared with compound AMR results at the completion of MVD. Results: Forty-two of 45 patients' AMR were recorded by compound AMR monitoring and 34 of 41 patients' AMR were recorded by single AMR monitoring during MVD. Hemifacial spasm resolved completely in 41 patients whose compound AMR was recorded and in 26 patients whose single AMR was recorded. Compound AMR gained a sensitivity of 96.3% and a specificity of 97.2%. Correspondingly, single AMR gained a sensitivity of 97.1% and a specificity of 86.3%. Conclusions: Our results suggest that compound AMR is more suitable than single AMR in MVD for HFS.