Michiyasu Suzuki

13. Development of a functional mapping method using focal cortical cooling in awake craniotomy

The aim of this study is to determine the usefulness of abnormal muscle response (AMR) and facial motor evoked potential (FMEP) monitoring in predicting outcomes in patients with hemifacial spasm (HFS) who undergo microvascular decompression (MVD). AMRs were recorded from the mentalis and orbicularis oculi muscles. FMEPs were recorded from the orbicularis oculi muscle by transcranial stimulation via corkscrew electrodes placed at positions C3 or C4 and Cz. In 40 95%) of 42 patients, in whom either the amplitude of AMRs decreased <50% or the FMEP amplitude ratios (post/pre MVD) were <100%, the HFS resolved postoperatively. The remaining two patients had recurrences of their spasm 3 months after surgery. In 14 (70%) of 20 of the patients with persistent AMR after MVD, HFS gradually decreased over a mean of 6 weeks and disappeared. On the other hand, in 19 (95%) of the 20 patients with resolved MR, HFS disappeared immediately after MVD. Thus, the AMR findings significantly correlated with postoperative courses (p < 0.001). Our results suggest that both AMR monitoring and FMEP monitoring predict outcomes after MVD in HFS patients. The AMR findings also predict whether the HFS disappears immediately or gradually after surgery.