中心溝近傍AVMにおける術中皮質SEP記録の有用性

USE OF CORTICAL SOMATOSENSORY EVOKED POTENTIALS IN SURGICAL TREATMENT OF AVMS IN AND AROUND THE CENTRAL SULCUS

　対側正中神経電気刺激により大脳皮質感覚野上の記録電極よりN1，P2なる電位が記録される。N1は頂点潜時約20msecの陰性波で大脳皮質3b野起源とされ，P2は頂点満時約24msecで1，2野起源とされている。このN1，P2成分には中心溝をはさんで位相の逆転がみられる。この電気生理学的性質を利用して中心溝近傍の動静脈奇形（以下AVM）の4症例で全麻手術中に中心溝の同定を試みた。その結果，種々の麻酔薬を含む薬剤の投与にもかかわらず全症例で目的とする電位の位相の逆転が記録され，中心溝が術中同定されたが，2例で放射線学的計測による推測とは一致がみられなかった。3症例で運動野の保護に注意を払いながらAVMの全摘出が行われ，手術後遺症は出現しなかった。1症例で摘出により重篤な神経症状の出現が危惧されたため，流入動脈遮断術に手術法を変更した。

Electric potentials named N1, P2 are recorded from electrodes on the primary sensory cortex when the contralateral median nerve is electrically stimulated transcutaneously at the wrist. N1 is negative wave about 20 msec in peak latency, de-rived from cortex area 3b, and P2 is positive wave about 24 msec in peak latency, elicited from area 1 and 2. These components will show phase reversals between two responses recorded from precentral and postcentral electrodes pairs. In this report, we attempted to recognize central fissure in 4 cases of arteriovenous malformation in sensori-motor cortex with the benefit of the intraoperative cortical SEPs. We obtained successful recording of phase reversal and identified central fissure in all cases, to whom several anesthetic agents which were said to affect SEP in latency and amplitude were administered continuously during operation. Electrophysiologically recognized central fissuresdid not coincide with central sulcus arteries those identified by angiographic measurements of two patients. Avoiding injury to the motor cortex, 3 AVMs were completely resected without causing additional neurological deficits. One case whose nidus was hidden into the motor cortex was given up for its resection. In this case the clipping of feeding vessels was chosen for the treatment. Di-rect monitoring of SEP gives us many additional informations to radiological landmarks concerning the place of sensorimotor cortex and the selection of the surgical approach to the paracentral lesion.