Intraoperative Neurophysiological Monitoring during Microvascular Decompression Surgery for Hemifacial Spasm

반쪽얼굴연축(Hemifacial spasm, HFS)은 반쪽얼굴근육이 불수의적, 간헐적 그리고 불규칙적으로 수축하는 질환으로서, 보통 눈둘레근육(orbicularis oculi muscle)에서 시작되어 점 차 반쪽얼굴의 모든 근육이 불수의적으로 수축하는 질환이 다.[1-4] 병리적으로, 이 질환은 뇌줄기로부터 얼굴신경(facial nerve)이 나오는 얼굴신경 기시부(Root exit zone, REZ)를 주Hemifacial spasm (HFS) is due to the vascular compression of the facial nerve at its root exit zone (REZ).Microvascular decompression (MVD) of the facial nerve near the REZ is an effective and curative treatment for HFS.In MVD for HFS, intraoperative neurophysiological monitoring (IONM) has two purposes.The first purpose is to prevent injury to neural structures such as the vestibulocochlear nerve and facial nerve during MVD surgery, which is possible through IONM of brainstem auditory evoked potentials and facial nerve electromyography (EMG).The second purpose is the unique feature of MVD for HFS, which is to assess and optimize the effectiveness of the vascular decompression.The purpose is achieved mainly through monitoring of abnormal facial nerve EMG that is called as lateral spread response (LSR) and is also partially possible through Z-L response, facial F-wave, and facial motor evoked potentials.Through IONM mentioned above, MVD can be developed as a more safe and effective treatment for HFS.