一次運動野近傍病変の手術における運動誘発電位モニタリングの意義について

Significance and Usefulness of Corticospinal Motor Evoked Potential Monitoring for Lesions Adjacent to Primary Motor Cortex

　要旨　運動野近傍髄内病変の摘出手術に際して術中錐体路誘発電位（MEP）を記録し，術中MEPの変化から術後運動機能を予測し得るか否かにつき検討した。一次運動野および錐体路近傍占拠性病変45例を対象とし，術中に一次運動野を電気刺激して頸髄硬膜外に挿入した電極からMEPを記録した。術前後の運動機能はDeJong分類で評価し，摘出終了時のMEP D-responseの振幅変化と比較検討した。

　術前運動機能がDeJong3以上の症例では全例MEPが記録できたが，DeJong2以下の高度運動機能障害例では記録は困難であった。摘出終了時D-responseの振幅が開始時のそれの50％以上に保たれれば，術後運動機能は温存され，50％以下に低下すると術後運動機能の悪化が認められた。

　運動野近傍腫瘍摘出術に際し，術中MEPが運動機能温存の指標となり，運動野近傍病変の治療成績向上の一助となり得る。

　This study evaluated the usefulness of intraoperative corticospinal motor evoked potential（MEP） monitoring in preventing postoperative motor deficits, and whether this procedure contributed to surgery on intrinsic brain lesions in the vicinity of the motor area. The subjects were 45 patients with brain tumors located in and around the primary motor area. MEP was recorded through the cervical epidural electrodes in response to stimulation of the motor cortex. The amplitude of D-response of MEP was compared at the beginning and at the end of surgery. Then MEP changes were divided into five groups ; “increase”, “no change”, “diminish”, “decrease” and “disappear”. We used the DeJong classification for qualitative analysis of motor function, and reviewed these findings in relation to the change in MEP. It was possible to record MEP when the preoperative motor weakness was DeJong 3 or better. There was no postoperative motor deficit when the MEP amplitude was preserved at better than 50% of a control amplitude. If the amplitude decreased to less than 50%, motor deficits were encoutered. When MEP amplitude increased during the surgery, preoperative motor weakness was improved after the surgery. It is concluded that there is little possibility of causing motor deficits even if tumor removal is aggressively pursued, as long as the amplitude of D-response remains at 50% or more of the baseline. This monitoring procedure is expected to improve the overall surgical results in patients with intrinsic brain tumors around the motor area.

（Received : April 7, 2004）