Preliminary results of fully endoscopic microvascular decompression with intraoperative neurophysiological monitoring

Abstract

Introduction: Endoscopic microvascular decompression (MVD) with intraoperative neurophysiological monitoring (IONM) is increasingly being adopted as the standard approach for treating neurovascular compression syndromes in the cerebellopontine angle. This study aims to evaluate the initial outcomes of the first five cases of endoscopic MVD with IONM.

Materials and Methods: This prospective study included the first five cases of endoscopic MVD with IONM performed for trigeminal neuralgia and hemifacial spasm at the Department of Neurosurgery – Spine surgery, Hanoi Medical University Hospital between September 2024 and February 2025. The neurophysiological monitoring techniques used included brainstem auditory evoked potentials (BAEP), brainstem trigeminal evoked potentials (BTEP), lateral spread response (LSR), and Zhong-Lee response (ZLR). Treatment outcomes for trigeminal neuralgia were assessed using the Barrow Neurological Institute (BNI) pain intensity scale, while hemifacial spasm outcomes were evaluated using the Hemifacial Spasm (HFS) score.

Results: Three cases of hemifacial spasm had a preoperative mean HFS clinical score of 12.67, which improved to 0 postoperatively, with a preoperative quality of life (QoL) of 73.3%, improving to 0% postoperatively. All three cases involved compression by the anterior inferior cerebellar artery (AICA) and exhibited intraoperative LSR, which disappeared after decompression, accompanied by a positive Zhong-Lee response. Two cases of medically refractory trigeminal neuralgia were classified as BNI grade IV and V preoperatively, with immediate postoperative improvement to BNI grade I. The compressing structures were the superior cerebellar artery (SCA) and Dandy’s vein. In both cases, BTEP waves in the V2 and V3 branches emerged following decompression. Although all five cases demonstrated intraoperative BAEP amplitude reduction,  postoperative hearing function was preserved.

Conclusions: Endoscopic MVD with IONM enhances surgical success rates and reduces postoperative hearing loss.

Keywords: trigeminal neuralgia, hemifacial spasm, endoscopic microvascular decompression, Jannetta procedure, intraoperative neurophysiological monitoring.

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