ネコ三叉神経誘発電位—記録方法と正常値

TECHNICAL DETAILS FOR RECORDING OF TRIGEMINAL EVOKED POTENTIALS IN CAT

　抄録　三叉神経痛の病態解明や治療効果の判定，また脳幹機能モニターなどをいずれも客観的に行なう手段として，三叉神経誘発電位（trigeminal evoked potentials：TEP）の有用性が期待される。そこでまずネコにおけるTEPの記録法を確立するとともにこの方法により記録したTEP各波の潜時の正常値を求めた。ネコの体温を直腸温で37.5〜38.5℃の間に保ちまた筋弛緩剤を投与し調節呼吸下に置いた。下眼窩神経を露出し遠位側を陽極に置いた双極の鈎電極にて，これに0.1msec・10Vの矩形波電気刺激を与えた。Inionを不関電極としTEPの短潜時成分はvertexより，長潜時成分は刺激と対側の顔面感覚領野からそれぞれ導出した。短潜時成分は5Hzの刺激頻度で刺激後10msecの間に誘発される電位を100〜3000Hzのband-pass filterを通じ250〜500回の加算平均を行なって記録した。また長潜時成分は2Hzの刺激頻度で，刺激後40msecまでの間に誘発される電位を0.5〜3000Hzのband-pass filterを通じ100〜200回の加算平均で得た。10匹のネコより得られた各頂点波潜時の平均値ならびに標準偏差は，P1：0.67±0.04msec, N1：0.89±0.07msec, P2：1.35±0.10msec, P3：1.89±0.08msec, P4：2.43±0.26msec, P5：3.17±0.15msec, P6：3.36±0.21msec, P7：5.02±0.39msec, P8：6.07±0.35msec, N2：10.4±1.15msec, N3：18.5±1.74msecであった。

Experiments were undertaken to establish tech-nical standards for recording of trigeminal evoked potentials (TEP) as a tool for assessment of the effectiveness of various therapeutic procedures for trigeminal neuralgia.

Serial changes in the action potentials of the maxillar nerve and TEP were studied when para-meters of electrical stimulation, namely, intensity and frequency, and position of electrodes were altered. The effects of use of muscle relaxants and change of body temperature of animals on TEP were also studied. On the basis of these experi-mental results, the technical details most suitable for TEP recording in cat were explored. The most distinct TEP was recorded under the follow-ing animal conditions and parameters : keeping rectal temperature between 37.5ﾟC and 38.5ﾟC, slackening with muscle relaxants, stimulating the infraorbital nerve with 10 volts of square-pulse electricity 5 times per second in short latency TEP and 2 times per second in long latency TEP, placing the active electrode on the vertex for short latency TEP and on the primary sensory area for long latency TEP.

Eight positive peaks and three negative peaks were recorded under these conditions. The average and standard deviations of peak latency of poten-tial from 10 cats were as follows : P 1, 0.67±0.04 msec ; N 1,0.89 ±0.07 msec ; P 2, 1.35 ± 0. 10 msec ; P 3, 1.89±0.08 msec ; P 4, 2.43±0.26 msec ; P 5, 3.17 ± 0.15 msec ; P 6, 3.36 ± 0.21 msec ; P 7, 5.02 ± 0.39 msec ; P 8, 6.07±0.35 msec ; N 2, 10.4 ±1.15 msec ; N 3, 18.5 ± 1.74 msec.

The origins of each peak in TEP recorded by this method will be reported elsewhere.