经颅磁刺激安全性的实验研究

Experimentalsafetystudiesoftranscranialmagneticstimulation

为证实经颅磁刺激（ＴＭＳ）的安全性，记录并分别分析了大鼠接受ＴＭＳ和头部阳极电刺激（ＥＢＳ）诱发时，后肢肌肉的复合肌肉动作电位（ＣＭＡＰｓ）。发现ＴＭＳ能够在大鼠引发ＣＭＡＰｓ，其阈刺激强度为最大输出的３４．５％，而头旁刺激不能引发ＣＭＡＰｓ；腰椎上方磁刺激可获得潜伏期远短于ＴＭＳ的ＣＭＡＰｓ。麻醉过深可抑制ＴＭＳ引发的ＣＭＡＰｓ。超强ＥＢＳ与ＴＭＳ所诱发的ＣＭＡＰｓ的潜伏期相差１．３ｍｓ。结果表明，ＴＭＳ可在大鼠脑组织中产生足够强度的诱导电流，因而适合于ＴＭＳ安全性的动物实验研究。在此基础上，初步观察了每天５０或１００次的ＴＭＳ连续刺激１～３天，对大鼠行为及脑皮层组织形态及超微结构的影响，发现１００次／天的ＴＭＳ连续作用３天，能够导致大鼠运动皮层产生光镜及电镜下的形态学改变。结果提示，在临床上应注意正确使用ＴＭＳ技术。

InordertodeterminethevalidityofWistarratsastheexperimentalanimalmodelinsafetystudiesoftranscranialmagneticstimulation(TMS),TMS-evokedCMAPswerestudiedandcomparedwiththoseevokedwithanodalelectricbrainstimulation(EBS)in16anesthetisedrats.TheCMAPswereelicitedbyTMSinthehindlimbsoftheratswithanaveragestimulusintensityof34.5%ofthemaximumoutputofthestimulatorandwithanaveragelatencyof6.6msatasupra-maximalintensity,1.4mslaterthanthoseevokedwithEBS.MagneticstimulationalsoevokedCMAPsofmuchshorterlatencies(2.4～3.4ms)whenthecoilwasplacedoverthelumbarregion,butdidnotelicitanyresponsesevenatthemaximumoutputwhenitwasputbesidethehead.ThosefindingssuggestthatTMSisabletoinduceelectriccurentofsuficientintensitywithintherat′sbrain.Preliminaryobservationsonneurologicalbehavioursandmorphologicalchangesofthebrainsweremadeinanother20ratswhichunderwent50or100TMSperdayattheintensityof100%ofmaximumoutputofthestimulatorfor1to3days.Theyalexhibitedasinglejerkoneachstimula-tionandafewoftheexperimentalratsshowedtemporaryclumsinesonwalking.Noneofthemhadseizures.Hemotoxylin-eosinstainingshowedslightchangesoftheneuronshapesandelectronmi-croscopicstudyrevealeddefinitedendriticswelingoftheastrocytesonlyinthegroupreceiving100TMSadayfor3days.Nomicrovaculeswerefoundinanyoftherats.ItisconsideredthatthebraindamagesmighttakeplaceafterlongdurationsandalargenumberofTMS,butitissafewhenusedinlowfrequency(1～2Hz)andwithin10stimuliasgeneralyusedinclinicallaboratories.WesuggestthattheTMStechniqueshouldbeusedcautiouslyinthepatientswithsevereacutebrainlesions.