聴神経腫瘍—脳神経外科の立場から考える，術中モニタリングとトレンドグラフを用いた手術戦略

Acoustic Neuroma:Surgical Strategy Using Intraoperative Monitoring and Trend Graphs from the Neurosurgery Perspective

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・聴神経腫瘍の外科治療において用いる，蝸牛ならびに顔面神経の「解剖と機能を見える化」する術前三次元融合画像と術中モニタリングは，摘出率の向上ならびに神経機能温存成績の向上に有効である．

・背側蝸牛神経核活動電位（DNAP）と顔面神経根誘発筋活動電位（FREMAP）の持続モニタリングは，現在の測定波形，最大振幅値を表示し，手術開始時点と比較しての温存率をリアルタイムで表示，記録し，かつ手術全工程の温存率のトレンドを表示する機能を有する．2つの神経機能が，温存率として「見える化」され，手術の全工程が一目でわかる．いつ，どこで，どの操作を行ったときに，どのように反応が低下し，どのように対処したら，どう回復したかを後方視的に解析可能である．

・本稿では，まず聴神経腫瘍の手術や術中モニタリングの原理原則を簡潔にまとめ，その上で神経損傷を来した代表症例を提示しながら神経損傷回避のための手術のポイントを総括する．

＊本論文中、［Video］マークのある図につきましては、関連する動画を見ることができます（公開期間：2028年8月まで）。

　This study assessed the efficacy of combining preoperative three-dimensional (3D) fusion imaging with continuous intraoperative neurophysiological monitoring to enhance the anatomical and functional visualization of cochlear and facial nerves during acoustic neuroma surgery. Data from 282 consecutive patients (2006-2023) were analyzed. In all cases, dorsal cochlear nucleus action potential (DNAP) and facial nerve root evoked electromyography (FREMAP) were continuously monitored. A novel system was implemented for real-time waveform visualization, tracking amplitude trends, and displaying nerve preservation rates, allowing for immediate identification of neural deterioration, causative maneuvers, and responses to surgical interventions. Preoperative 3D fusion imaging was performed in 199 cases, and nerve trajectory visualization was achieved in 65% of these cases. A comprehensive database integrating clinical and intraoperative data was created, and multivariate analyses was performed to identify predictors of postoperative function. Final DNAP and FREMAP preservation rates were significantly associated with hearing and facial nerve outcomes, respectively. Optimal DNAP and FREMAP thresholds, as determined using receiver operating characteristic (ROC) analysis, were ≥ 35.5% and ≥ 58.5%, respectively. These findings support the utility of real-time, continuous neurophysiological monitoring and preoperative imaging in improving nerve preservation. The surgical techniques and monitoring strategies are demonstrated in the accompanying video.