01-박윤길/종설/1-5

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1 J Korean EMG Electrodiagn Med 대한근전도 전기진단의학회지 15(1):1~5, 2013 연세대학교의과대학재활의학교실및희귀난치성신경근육병재활연구소 Abstract Intraoperative Neurophysiological Monitoring Park, Yoon Ghil, M.D., Ph.D. Department of Rehabilitation Medicine and the Rehabilitation Institute of Neuromuscular Disease, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea Intraoperative neurophysiological monitoring (IONM) is a valuable tool to prevent damage by detecting dysfunction before reaching an irreversible stage in brain, spine and other surgical procedures. This article focuses on the intraoperative application and clinical utility of somatosensory evoked potentials (SEP), motor evoked potentials (tcmep) and triggered and spontaneous EMG. Somatosensory evoked potential (SEP) monitoring used in several decades helped to prevent neurologic deficits. However, motor compromise can occur without SEP warning and SEP deterioration can occur without motor deficit. Intraoperative MEP monitoring in patients with spinal and cranial lesions is thought to be a valuable tool for prevention of postoperative motor deficits. In recent years, motor evoked potential recording following transcranial electrical stimulation has emerged as a reliable technique to intraoperatively assess the functional integrity of the motor pathways.spontaneous and triggered EMG is getting widely used as a means of monitoring nerve root function during spine surgery. Although IONM is a valuable technique that provides sensitive and specific indications of neurologic injury, it does have limitations that must be understood. The monitoring team must be well trained, be able to provide the surgeon feedback in real time, and coordinate activities with those of the surgical and anesthesia teams. Key Words: Intraoperative neurophysiological monitoring, Somatosensory evoked potential, Motor evoked potentials, Spontaneous EMG, Triggered EMG (Intraoperative Neurophysiological Monitoring, IONM) 는수술중신경계손상을방지하고자하는시행하는감시방법으로척추와뇌수술에주로적용이되었으나최근말초신경이 나이비인후과수술등다른여러분야로확장되어이용되고있다. 마취분야에서시행되는수술중감시방법과구별하기위해서수술중감시 (Intraoperative Monitoring, IOM) 보다로표기하 Address reprint requests to Park, Yoon Ghil, M.D.,Ph.D. Department of Rehabilitation Medicine and the Rehabilitation Institute of Neuromuscular Disease, Gangnam Severance Hospital, Yonsei University College of Medicine, 712 Eonjuro, Gangnam-gu, Seoul , Korea TEL: , FAX: , drtlc@yuhs.ac 투고일 : 2013년 5월 13일, 수정일 : 2013년 5월 13일, 게재확정일 : 2013년 5월 13 일 1

2 는것이정확하고건강보험요양급여에서도이러한명칭으로분류하고있으나아직많은문헌에서혼재되어표기되고있다. 의목적은언급한바와같이신경계손상의빈도와정도를감소시키는데대체적으로다음과같이세가지로정리할수있다. 1) 신경계자극과조직손상을감지하여손상을최소화하고회복가능하게한다. 2) 신경계손상을가능한조기에발견하여수술과정을변경하거나중단하도록한다. 3) 수술자가신경조직을감지하지못하고있을때이를확인하는것을도와준다. 1 이와같이는신경계손상이가역적인상태에있을때수술자에게알려줌으로써영구적인손상을예방하는데있다. 임상적으로는뇌파 (electroencephalogram, EEG) 가가장먼저이용되었고이후체성감각유발전위 (somatosensory evoked potential, SEP), 뇌간청각유발전위 (brainstem auditory evoked potential, BAEP) 및근전도 (electromyography, EMG) 가여러영역에서사용되었으며최근운동신경유발전위 (motor evoked potential, MEP) 이운동신경기능감시에이용되고있다. 본문에서는일반적으로많이이용되고있는 SEP, MEP, EMG를중심으로기술하기로한다. 1. 체성감각유발전위 (SEP) SEP 는촉각, 진동과고유수용체감각을전달하는척수후주의기능을평가하는검사로오래전부터방법으로이용되었으며현재도가장널리이용되는검사법이다. 일반적으로팔에서는정중신경또는척골신경을, 다리에서는경골신경또는비골신경을자극한다. 두피에서기록은 international system을기준으로하지신경자극시에는 Cz -Fz, 상지신경자극시에는 C3 /C4 -Fz 에서주로시행하며, 전기자극은 ms의지속시간과 ma의강도로자극을한다. 2 일반적으로 SEP 의경우진폭이 50% 이상지속적으로감소된경우나잠시가 10% 이상늘어난경우를의미있는변화로간주하는데 3 이외에도 CCT 가 1 ms 이상증가되었거나기준치의 20% 이상늘어난경우와주요파형이왜곡된경우 (desynchronization) 에도의미있는지표로인정해야된다는보고도있다. 4,5 경골신경 SEP 의경우 P37/N45, 정중신경 SEP 경우에는 N20/P22 전위가주요지표로이용된다. SEP 는후주를통과하는감각신경로를감시하는것은유용하나척수의운동신경통로를감시하는대는한계가있어서위음성이항시문제가되고있다. 또한지속적인실기간검사가가능한장점을가지고있으나 Hilibrand 등 6 의연구에의하면 MEP 의변화보다평균 16 분늦게반응을나타낸다고되어있어신경학적변화가상당히진행된후에감시자가인지할수있는단점도가지고있다 년 Nuwer 등 7 은다기관연구를통해 51,263 명의척추측만증수술중 SEP 감시는수술후새로운신경학적인증상발생에대한민감도가 92% 이며특이도가 98.9% 라하였으며, 최근연구들은척추수술에서 SEP 의민감도는 0~52%, 특이도는 95~100% 로보고되고있다. 6, Transcranial motor-evoked potential (tcmep) 앞서언급한바와같이수술중에 SEP 가정상범위임에도불구하고운동신경계의이상이나타날수있으므로이를감시할수있는 MEP 가필요하게되었다. 11,12 MEP 방법중척수자극기법 (spinal cord stimulation) 은운동신경뿐만아니라감각신경도자극하게되고이와더불어 Ia 섬유를통해말초신경을자극하여다른경로로근육섬유수축을일으키므로수술중정확한판단을하기어려운점이있었다. 11 이에비해경두개전기자극 (transcranial electrical stimulation, tcmep) 이나경두개자기자극 (transcranial magnetic stimulation, TMS) 은감각신경계의유발전위발생없이대뇌의운동영역을자극할수있는장점이있으며, 이중전기자극방법이더효과적이고실용적이기때문에많이이용되고있다. 13 tcmep 는양극 (anode) 부위에서활성전위 (action potential) 가형성되기때문에일반적인신경전도검사와달리항상양극을기준으로하며이를통해좌우근수측반응을구분하는것을유념해야한다. 자극위치를표기할때도통상적으로양극을음극 (cathode) 앞에놓는데자극위치는 SEP 와달리아직표준화된것이없으나 C3/C4 나 C1/C2 형태를많이사용하며, 앞서언급한바와같은이유로해서 C3/C4 인경우우측근육에서반응을측정하게되고 C4/C3 는반대가된다. 자극강도는 0.5 ms 의지속시간과 V ( ma) 의자극강도로시행하는데척수에서하행성피질척수로의반응 (D 파 ) 을기록하는방법과근육에서복합근활동전위 (compound muscle action potential, CMAP) 를기록하는방법이주로사용되고있다. 마취상태에서는일회전기자극으로는 D 파외에근육 CMAP 을형성할수없기때문에보통 4msec 의간격으로 4 회이상연속자극을주게된다. 14 D 파는마취에영향을적게받고대뇌자극빈도와같이일정하게반응하는장점이있는반면에척추수술의경우지속적으 2

3 로전극을위치시키기어렵고임상양상과다른결과를보이는단점이있다. 상하지에서 CMAP 을측정하는것은마취상태, 특히근육이완제의영향을많이받게되나충추신경계손상뿐만아니라신경근을포함한말초신경계까지감시할수있는장점이있고실제임상결과와밀접한관계가있어서 D 파검사보다는널리이용되는방법이다 (Fig. 1). 15 여러연구자들이 SEP 와같이 MEP 에서도 50% 이상의진폭의변화가있을때나잠시가 10% 이상연장되었을때를의미있는변화로받아들이나, 자극강도를 20% 이상증가시키거나 160 ma 보다강하게자극해야파형이유지되는경우도임계점으로보고한최근연구도있다. 16 그러나척수수술의경우 all-or-none rule 을적용하는경우도많다 MEP 의민감도와특이도는임계점의기준에따라달라질수있으나최근연구들에의하면민감도는 75~100%, 특이도는 84~100% 로보고되고있다. 3 MEP 는 SEP 와달리지속적으로자극을보내어결과를볼수있는것이아니고수술자가요청할때시행하는것이므로신경손상이이미진행된상태에서결과를확인하게되는경우가발생할수있다. MacDonald 등 11 이 15,000 건의 tcmep 의부작용사례를조사해본결과경련 (seizure) 은 5 건으로드물게나타났는데이는매우짧은시간에자극이가해지기때문으로해석되었다. 가장많이나타난부작용은혀와입술의자상으로이를방지하기위해서는구강내장치를사용해야하며, 이외에도심장이상, 두피화상등이드물게나타났다. 3. 자발근전도 (Free running EMG) 말초신경자극에의한해당근육의반응을보는방법으로척추수술중신경근의기능을확인하는데쓰이게된다. 주로신경근과해당근육을 1:1 로맞추어서시행하지만위험도가높은신경근의경우 2 개의근육을감시하기도한다. 3 수술중연속해서실시간으로감시가가능한장점이있지만체온변화와전기소작등에따른위양성이있기때문에특이도가떨어지는문제점이있다 유발근전도 (Triggered EMG) Pedicle 나사를이용한척수수술에서나사에의한신경근손상이일어날수있는데, 이를방지하기위하여나사를전기적으로자극하여복합근활동전위가유발되는역치를평가하는것이유발근전도의개요이다. Pedicel 나사가정확히위치하게되면주위의골조직이전기적신호전달의절연체로작용하여주위의신경근을자극하려면자극강도가높아지고반대로신경근가까이나사가접근하게되면자극강도가떨어지게되는데 8.0 ma 이상일경우 99.5~99.8% 에서정확한위치에있다는보고가있다 수술중감시에영향을주는요소 Fig. 1. Intraoperative methodology for eliciting and recording motor evoked potential from the spinal cord and limb muscles. 15 1) 혈류량경동맥내막절제술 (carotid endarterectomy, CEA) 를시행하면서뇌혈류량 (regional cerebral blood flow, rcbf) 을측정한결과 rcbf가 10 ml/100 g/min 미만인경우뇌파의주요한변화가나타나고 10~18 ml/100 g/min인경우에는심각하지않은뇌파의변화가나타나는것으로관찰되어 rcbf이 15 20, 21 ml/100 g/min일때가임계점으로여겨지고있다. 이러한현상은영장류를이용한 SEP 실험에서도비슷한경향을보이는데 rcbf가 16 ml/100 g/min 이상일경우는파형이유지가되지만 12 ml/100 g/min 미만인경우는소실되고 14~16 ml/100 g/min에서는급격히진폭이감소하는데 rcbf가 16 ml/100 g/min 일때진폭의 50% 감소가나타나는것으로관찰 3

4 되었다. 22,23 또한 rcbf가 15 ml/100 g/min 이하로떨어질때진폭의감소와더불어 CCT의연장이나타난다. 24 따라서수술중출혈에의한저혈압에의해 SEP 의진폭이감소되고잠시가연장될수있음을유의해야한다. 25 2) 마취를위해서는 propofol 이나 fentanyl 을이용한정맥내마취가운동신경원에영향을적게주기때문에가장적절한방법이며, 흡입성마취제는대뇌피질의흥분도를억제하여 SEP 의진폭을감소시키고잠시를연장시키기때문에적절한감시를할수없게된다. 14 기도삽관을포함한마취유도시지속시간이짧은근이완제사용하는것이외에는신경근이완제도사용하지말아야근육 MEP 를측정할수있다. 3) 체온저체온은말초신경과중추신경의전도속도를떨어뜨리기때문에잠시를연장시킬수있는데보통여러가지원인으로수술중에는체온이감소하므로이에따른대비를해야적절한감시가이루어진다. 25 맺음말 최근전산장비의발전에의해전기진단검사장비도많은개선이이루어졌는데특히수술중감시장치는빠른속도의컴퓨터와양질의증폭기로인해실시간모니터링이가능해졌고잡음 (noise) 도적어져예전과같이수술을중단하고감시장치를확인하던불편이없어졌다. 또한 16 채널이상의장비가도입되면서수술중전극을교체해야하는문제도사라졌다. 그럼에도불구하고수술실내여러장비들에의한방해전파는여전히해결해야될과제이며공간부족과이동성문제를해결하기위해서는작은크기의간편한장비가개발되어야하겠다. 장비외에도전문인력의확보는가장핵심적인요소인데현재의수가와인력으로는신경과나재활의학과전문의가수술실에서계속감시하는것은현실적으로불가능하므로잘훈련된전문인력이수술실에상주하면서밖에있는전문의와상의하는 telemedicine monitoring 이이루어져야원활한수술중감시장치활용이이루어질것으로판단된다. 이와더불어현재는지정된몇몇특정질환이나수술법만이를이용한급여를청구할수있는데, 적응증을확대를통해빠르게발전하는수술기법을안전하게시행하게도움으로써환자의건강권을확보하는것이당면한문제라고판단된다. REFERENCES 1. Daube JR: Intraoperative monitoring reduces complications and is therefore useful. Muscle Nerve 1999: 22: 손민균 : Spinal Operative Monitoring. 2009년대한재활의학회추계학술대회, 서울 : 대한재활의학회 2009, pp Lall RR, Lall RR, Hauptman JS, Munoz C, Cybulski GR, Koski T, et al: Intraoperative neurophysiological monitoring in spine surgery: indications, efficacy, and role of the preoperative checklist. Neurosurg Focus 2012: 33: E Florence G, Guerit JM, Gueguen B: Electroencephalography (EEG) and somatosensory evoked potentials (SEP) to prevent cerebral ischaemia in the operating room. Neurophysiol Clin 2004: 34: Guerit JM, Witdoeckt C, de Tourtchaninoff M, Ghariani S, Matta A, Dion R, et al: Somatosensory evoked potential monitoring in carotid surgery. I. Relationships between qualitative SEP alterations and intraoperative events. Electroencephalogr Clin Neurophysiol 1997: 104: Hilibrand AS, Schwartz DM, Sethuraman V, Vaccaro AR, Albert TJ: Comparison of transcranial electric motor and somatosensory evoked potential monitoring during cervical spine surgery. The Journal of bone and joint surgery American volume 2004: 86-A: Staudt LA, Nuwer MR, Peacock WJ: Intraoperative monitoring during selective posterior rhizotomy: technique and patient outcome. Electroencephalogr Clin Neurophysiol 1995: 97: Gunnarsson T, Krassioukov AV, Sarjeant R, Fehlings MG: Real-time continuous intraoperative electromyographic and somatosensory evoked potential recordings in spinal surgery: correlation of clinical and electrophysiologic findings in a prospective, consecutive series of 213 cases. Spine (Phila Pa 1976) 2004: 29: Kelleher MO, Tan G, Sarjeant R, Fehlings MG: Predictive value of intraoperative neurophysiological monitoring during cervical spine surgery: a prospective analysis of 1055 consecutive patients. J Neurosurg Spine 2008: 8: Park P, Wang AC, Sangala JR, Kim SM, Hervey-Jumper S, Than KD, et al: Impact of multimodal intraoperative monitoring during correction of symptomatic cervical or cervicothoracic kyphosis. J Neurosurg Spine 2011: 14: MacDonald DB: Safety of intraoperative transcranial electrical stimulation motor evoked potential monitoring. J Clin Neurophysiol 2002: 19:

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00유발전위-부속 V,,,,,,. 1929 Hans Berger,, Dawson. 1976, Dr. Drake Dr. Peerless, Dr. Barnett 1979 2 fellow 1980 Havard Dr. Chiappa Evoked potentials. Dr. Drake,. 1981,,,, conference. 1981 7 Nicolet. 1983 9 21~24 Tulsa,