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Electrically evoked motor potentials (MEP) during surgical monitoring
Se+m
4.7:
htraoperative Monitoring1
43-02 i~trao~~rativ~
Electrodiagnosis for Brachial Plexus l~j~r~e~~ Making Use of Spinal SEP
Koichi Funakoshi *, .Akira M~yauchi *, Hideo Matsuda **, Nobuaki Nakata **, Akira Shimazu **. *De~atiment of Otthopaedic Surgery Osaka Shakai llyo Center; ** Departmen; of Orthopaedic Surgery, Osaka City University It is necessary to investiga?e nerve root functions, on surgical treatment for brachial plexus injuries (BPI). We recorded spinal SEPs during operations, in addition to cortical SEP with root stimulation and motor evoked potential (MEP) with transcranial stimulation (TCS). Pat/en& and Methods; 63 patients were operated on for BPI, followed the result of spinal SEF! There were 60 men and 3 women, and the average age was 20.4 years old. 54 of 63 patients (85.7%) were injured in motorcycle accidents. The equipment was Evomatic 8000. Cortical SEP. spinal SEP (X2-Fz, YL-Frj and ESCP were recorded with root stimulation, and root potnntials were recorded with TCS and with spinal cord stimulation at the level of Coil or Cl/Z. Resuits: Spinal SEPs are less susceptible to anesthesia than cortical SEPs. In 12 of 65 (18.5%). we did root repair, and neurolysis. nerve-transfer and nen/e graft at the distal level of plexus were done in 4 (6.1%), in 33 (50.8%) and in 16 (24.6%) respectively. lntraoperative diagnosis showed that 20 of 42 CS-roots didn’t have enough function, though all of them were intact in myelography. 20 of them were given up to do root repair and nervetransfers were performed. We evaiuated the outcome of C5 root repair, using the muscle strength of biceps. 80% patients recovered over 3 (MMT) of it, since root repairs were decided by evaluation of cortical and spinal SEF: though 69.8% patients recovered when they were done only with cortical SEt?
43-03
~~trao~erative Monitoring of Evoked Spinal Cord Potentials Directly Recorded from the Dural Surface during Spinal Operation - In Surgical Cases of I Spondylosis and Spinal Cord Tumor
T. Goya, T. Mikura. S. Makihara, S. Wakisaka. Department Miyazaki Medical College, ,Miyasaki, Japan
ofNeurosurgew
lntraoperative monitoring of evoked spinal cord potentials (ESCP) became getting popular for safer soinal operation. We have been monitoring EPCP during various spinal operations. Especially, monitoring ESCP was very helpful on removal of the intramedullary spinal cord tumor. On the posterior approach to the spinal cord, ESCPs were recorded directly from the posterior dural surface before and after decompressive laminoplasty or iaminectomy. On the anterior approach to the cervical spine, recording electrodes were inserted in advance into the posterior epidural space with epidural anesthesia method on the day before the operation. During the operation, recordings were performed directly from the anterior dural surface after dissectomy, and simultaneouslyfrom the posterior epidural electrodes. ESCPs were divided into segmental and conductive components. Waveforms of ESCP obtained from the posterior aspect had distinct peaks of PI (9 ms), Nla, Nib, and P2. PI-Nla component was conductive one. Nlb was segmentally modulated potential near the root entry portion. Waveforms obtained from the anterior dural surface included PI, Nl, P2 and N2 components. Posterior Nla corresponded to anterior Nl I posterior Nl b, to anterior P2. and posterior P2, to anterior N’2 respectively. Components with reversed polarity between anterior and posterior recordings were potentials modulated locally near the root entry portion. In patients with myelopathy, distinction of posterior Nla and Nlb was unclear, Even in such case, anterior Nl was clearly recorded. On removal of the intramedullarytumor, manipulation of the spinal cord was allowable under the presence of recognizable responses.
/ 43 04
Effects af Volatile Anaesthetics on the Motor Evoked potential Recorded Using Epidural Electrodes
Richard Hicks, David Burke, Ian Woodforth. Matthew Crawford, John Stephen. The Prince of Wales Hospital, Sydne)! Australia The motor evoked potential (MEP). recorded from bipolar epidural electrodes in response to Vanscranial electrical stimulation, is composed of a D wave (the component of lowest threshold) followed by I waves (resulting from trans-synaptic activation of corticospinal neurones).
We studied the responses in 50 patients (35F; 15M) undergoing spinal surgery when the end-tidal anaesthetic concentrations of isoflurane, enflurane and halothane were reduced to 0%. All three volatile anaesthetic agents have similar effects on the MEF! Major changes were scan ili the Iiminal D wave, consisting of a marked increase in amplitlrde as the concentration was reduced to 0% Proportionately smailer amplitude changes were seen in supraliminai D waves, although in many cases the 5 wave became bifid or even trifid as short-latency components emerged due to subcortical activation. In general, the effect on the D wave of withdrawing a volatile anaesthetic agent was similar to that of increasing stimulus intensity, Decreasing the concentrations of the volatile agents led to an increase in both the number and amplitude of I waves, but also changed the relative amplitudes of individual I waves and altered their latencies. In all cases the greatest changes were seen with concentrations between O-0.5%. The stability of the supraliminal D wave at the concentrations of these anaesthetics required for surgery provides further evidence for the reliability of epidural recordings in the clinical situation.
/ 43-05
) Electrically Evoked Motor ~Qt~R~~~~s( Surgical Monitoring
William J. Litchy, C. Michael Harper, Jasper R. /Da&e. Foundation, Rochester, Minnesota, USA 55905
,&?a~~ !XZc,
itiaayo
Thirty patients had combined SEP and MEP testing during thoracic and lumbar spine surgery under Fentanyl anesthesia. MEP were elicited by direct electrical stimulation of the spinal cord with electrodes on the lamina of the C7 spine posteriorly and in the esophagus anterioriy. Paired stimuli at a 3.0 msec interval with durations of 1 .O msec were applied repeatedly at slow rates at the surgeons request. Surface recordings from leg muscles were made bilaterally. A partial neuromuscular block with a TI of 20% was maintained throughout the procedures. Reproducible responses to single shocks were obtained in 27 patients. In two there was inadequate relaxation and control of spontaneous movements that precluded continued MEP testing. Simultaneous F-wave and H-reflex responses were usually lost early in the recording. This study shows that percutaneous electrical stimulation can reliably evoke MEP in the lower extremities.
/43-06 ]lntraoperative Monitoring in AC Surgery in the Semi-Sitting Cordula Matthies, Madjid Samii. Department Hospital, Hannover, ER.Germany
~~~~t~~~ ofNeurosurge~
Nordstadt
Since the introduction of microsurgical techniques mortality rates in cerebellopontine angle tumors have markedly been lowered, and the decrease of morbidity, with the aid of neurophysiological monitoring. is the major goal. Facial nerve monitoring by facial electromyography can be useful especially in large tumors or in pre-operated cases, and may help understanding the pathological anatomy. The cochlear nerve is one of the most sensitive nerves, extremely vulnerable to minor manipulations; its anatomical preservation does not necessarily imply preserved auditory function. Monitoring of brainstem auditory evoked potentials (SAEP) yields the oppoiltiinity to gain information on the functional changes during distinct surgical manipuiations. Monitoring of median and/or tibia1 nerve somatosensory evoked potentials [SSEP) offer intraoperative control of some spinal cord functions during operations in the semi-sitting position, a position that offers tremendous technical advantages to the surgeon, but has potentially severe side effects, i e. air embolism and/or tetraplegia. In the application of neurophysiological techniques and in the interpretation of neurophysiological data intraoperatively, special cooperation between the surgeon and the neurophysiologist are indispensib!e in order to minimize problems from electrical artefact sources, from delay in new evoked potential informations, from reduced reliability. After an enthusiastic start in the eighties, a number of investigators meanwhile doubt in the reliability and usefulness of monitoring. The present study was undertaken on 100 acoustic neurinoma resections. Besides continuous BAEP recordings performed in each case, facial nerve monitoring was applied in case of impaired preoperative facial nerve function and in case of large (above 3 cm of diameter) or cystic tumors, and SSEP recordings ‘were used additionally in the last 30 cases. lntraoperative waveform changes or wave losses were classified according to a special evoked potential grading system and were correlated with specific surgical actions. Hereby, anaiysis was performed on
4.7:
htraoperative Monitoring1
43-02 i~trao~~rativ~
Electrodiagnosis for Brachial Plexus l~j~r~e~~ Making Use of Spinal SEP
Koichi Funakoshi *, .Akira M~yauchi *, Hideo Matsuda **, Nobuaki Nakata **, Akira Shimazu **. *De~atiment of Otthopaedic Surgery Osaka Shakai llyo Center; ** Departmen; of Orthopaedic Surgery, Osaka City University It is necessary to investiga?e nerve root functions, on surgical treatment for brachial plexus injuries (BPI). We recorded spinal SEPs during operations, in addition to cortical SEP with root stimulation and motor evoked potential (MEP) with transcranial stimulation (TCS). Pat/en& and Methods; 63 patients were operated on for BPI, followed the result of spinal SEF! There were 60 men and 3 women, and the average age was 20.4 years old. 54 of 63 patients (85.7%) were injured in motorcycle accidents. The equipment was Evomatic 8000. Cortical SEP. spinal SEP (X2-Fz, YL-Frj and ESCP were recorded with root stimulation, and root potnntials were recorded with TCS and with spinal cord stimulation at the level of Coil or Cl/Z. Resuits: Spinal SEPs are less susceptible to anesthesia than cortical SEPs. In 12 of 65 (18.5%). we did root repair, and neurolysis. nerve-transfer and nen/e graft at the distal level of plexus were done in 4 (6.1%), in 33 (50.8%) and in 16 (24.6%) respectively. lntraoperative diagnosis showed that 20 of 42 CS-roots didn’t have enough function, though all of them were intact in myelography. 20 of them were given up to do root repair and nervetransfers were performed. We evaiuated the outcome of C5 root repair, using the muscle strength of biceps. 80% patients recovered over 3 (MMT) of it, since root repairs were decided by evaluation of cortical and spinal SEF: though 69.8% patients recovered when they were done only with cortical SEt?
43-03
~~trao~erative Monitoring of Evoked Spinal Cord Potentials Directly Recorded from the Dural Surface during Spinal Operation - In Surgical Cases of I Spondylosis and Spinal Cord Tumor
T. Goya, T. Mikura. S. Makihara, S. Wakisaka. Department Miyazaki Medical College, ,Miyasaki, Japan
ofNeurosurgew
lntraoperative monitoring of evoked spinal cord potentials (ESCP) became getting popular for safer soinal operation. We have been monitoring EPCP during various spinal operations. Especially, monitoring ESCP was very helpful on removal of the intramedullary spinal cord tumor. On the posterior approach to the spinal cord, ESCPs were recorded directly from the posterior dural surface before and after decompressive laminoplasty or iaminectomy. On the anterior approach to the cervical spine, recording electrodes were inserted in advance into the posterior epidural space with epidural anesthesia method on the day before the operation. During the operation, recordings were performed directly from the anterior dural surface after dissectomy, and simultaneouslyfrom the posterior epidural electrodes. ESCPs were divided into segmental and conductive components. Waveforms of ESCP obtained from the posterior aspect had distinct peaks of PI (9 ms), Nla, Nib, and P2. PI-Nla component was conductive one. Nlb was segmentally modulated potential near the root entry portion. Waveforms obtained from the anterior dural surface included PI, Nl, P2 and N2 components. Posterior Nla corresponded to anterior Nl I posterior Nl b, to anterior P2. and posterior P2, to anterior N’2 respectively. Components with reversed polarity between anterior and posterior recordings were potentials modulated locally near the root entry portion. In patients with myelopathy, distinction of posterior Nla and Nlb was unclear, Even in such case, anterior Nl was clearly recorded. On removal of the intramedullarytumor, manipulation of the spinal cord was allowable under the presence of recognizable responses.
/ 43 04
Effects af Volatile Anaesthetics on the Motor Evoked potential Recorded Using Epidural Electrodes
Richard Hicks, David Burke, Ian Woodforth. Matthew Crawford, John Stephen. The Prince of Wales Hospital, Sydne)! Australia The motor evoked potential (MEP). recorded from bipolar epidural electrodes in response to Vanscranial electrical stimulation, is composed of a D wave (the component of lowest threshold) followed by I waves (resulting from trans-synaptic activation of corticospinal neurones).
We studied the responses in 50 patients (35F; 15M) undergoing spinal surgery when the end-tidal anaesthetic concentrations of isoflurane, enflurane and halothane were reduced to 0%. All three volatile anaesthetic agents have similar effects on the MEF! Major changes were scan ili the Iiminal D wave, consisting of a marked increase in amplitlrde as the concentration was reduced to 0% Proportionately smailer amplitude changes were seen in supraliminai D waves, although in many cases the 5 wave became bifid or even trifid as short-latency components emerged due to subcortical activation. In general, the effect on the D wave of withdrawing a volatile anaesthetic agent was similar to that of increasing stimulus intensity, Decreasing the concentrations of the volatile agents led to an increase in both the number and amplitude of I waves, but also changed the relative amplitudes of individual I waves and altered their latencies. In all cases the greatest changes were seen with concentrations between O-0.5%. The stability of the supraliminal D wave at the concentrations of these anaesthetics required for surgery provides further evidence for the reliability of epidural recordings in the clinical situation.
/ 43-05
) Electrically Evoked Motor ~Qt~R~~~~s( Surgical Monitoring
William J. Litchy, C. Michael Harper, Jasper R. /Da&e. Foundation, Rochester, Minnesota, USA 55905
,&?a~~ !XZc,
itiaayo
Thirty patients had combined SEP and MEP testing during thoracic and lumbar spine surgery under Fentanyl anesthesia. MEP were elicited by direct electrical stimulation of the spinal cord with electrodes on the lamina of the C7 spine posteriorly and in the esophagus anterioriy. Paired stimuli at a 3.0 msec interval with durations of 1 .O msec were applied repeatedly at slow rates at the surgeons request. Surface recordings from leg muscles were made bilaterally. A partial neuromuscular block with a TI of 20% was maintained throughout the procedures. Reproducible responses to single shocks were obtained in 27 patients. In two there was inadequate relaxation and control of spontaneous movements that precluded continued MEP testing. Simultaneous F-wave and H-reflex responses were usually lost early in the recording. This study shows that percutaneous electrical stimulation can reliably evoke MEP in the lower extremities.
/43-06 ]lntraoperative Monitoring in AC Surgery in the Semi-Sitting Cordula Matthies, Madjid Samii. Department Hospital, Hannover, ER.Germany
~~~~t~~~ ofNeurosurge~
Nordstadt
Since the introduction of microsurgical techniques mortality rates in cerebellopontine angle tumors have markedly been lowered, and the decrease of morbidity, with the aid of neurophysiological monitoring. is the major goal. Facial nerve monitoring by facial electromyography can be useful especially in large tumors or in pre-operated cases, and may help understanding the pathological anatomy. The cochlear nerve is one of the most sensitive nerves, extremely vulnerable to minor manipulations; its anatomical preservation does not necessarily imply preserved auditory function. Monitoring of brainstem auditory evoked potentials (SAEP) yields the oppoiltiinity to gain information on the functional changes during distinct surgical manipuiations. Monitoring of median and/or tibia1 nerve somatosensory evoked potentials [SSEP) offer intraoperative control of some spinal cord functions during operations in the semi-sitting position, a position that offers tremendous technical advantages to the surgeon, but has potentially severe side effects, i e. air embolism and/or tetraplegia. In the application of neurophysiological techniques and in the interpretation of neurophysiological data intraoperatively, special cooperation between the surgeon and the neurophysiologist are indispensib!e in order to minimize problems from electrical artefact sources, from delay in new evoked potential informations, from reduced reliability. After an enthusiastic start in the eighties, a number of investigators meanwhile doubt in the reliability and usefulness of monitoring. The present study was undertaken on 100 acoustic neurinoma resections. Besides continuous BAEP recordings performed in each case, facial nerve monitoring was applied in case of impaired preoperative facial nerve function and in case of large (above 3 cm of diameter) or cystic tumors, and SSEP recordings ‘were used additionally in the last 30 cases. lntraoperative waveform changes or wave losses were classified according to a special evoked potential grading system and were correlated with specific surgical actions. Hereby, anaiysis was performed on