- Department of Neurosurgery, Shioya Hospital, International University of Health and Welfare, Yaita, Tochigi, Japan
- Department of Neurosurgery, Jichi Medical University, Shimotsuke, Tochigi, Japan
- Department of Clinical Laboratory, Kitasato University, The Kitasato Institute Medical Center Hospital, Kitamoto, Saitama, Japan
- Department of Neurosurgery, Tokyo Rosai Hospital, Ohta, Tokyo, Japan
Department of Neurosurgery, Tokyo Rosai Hospital, Ohta, Tokyo, Japan
DOI:10.4103/2152-7806.83731Copyright: © 2011 Tanaka S. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Tanaka S, Tashiro T, Gomi A, Takanashi J, Ujiie H. Sensitivity and specificity in transcranial motor-evoked potential monitoring during neurosurgical operations. Surg Neurol Int 13-Aug-2011;2:111
How to cite this URL: Tanaka S, Tashiro T, Gomi A, Takanashi J, Ujiie H. Sensitivity and specificity in transcranial motor-evoked potential monitoring during neurosurgical operations. Surg Neurol Int 13-Aug-2011;2:111. Available from: http://sni.wpengine.com/surgicalint_articles/sensitivity-and-specificity-in-transcranial-motor-evoked-potential-monitoring-during-neurosurgical-operations/
Background:Intraoperative transcranial motor-evoked potential (TCMEP) monitoring is widely performed during neurosurgical operations. Sensitivity and specificity in TCMEP during neurosurgical operations were examined according to the type of operation.
Methods:TCMEP monitoring was performed during 283 neurosurgical operations for patients without preoperative motor palsy, including 121 spinal operations, 84 cerebral aneurysmal operations, and 31 brain tumor operations. Transcranial stimulation at 100–600 V was applied by screw electrodes placed in the scalp and electromyographic responses were recorded with surface electrodes placed on the affected muscles. To exclude the effects of muscle relaxants on TCMEP, compound muscle action potential (CMAP) by supramaximal stimulation of the peripheral nerve immediately after transcranial stimulation was used for compensation of TCMEP.
Results:In spinal operations, with an 80% reduction in amplitude as the threshold for motor palsy, the sensitivity and specificity with CMAP compensation were 100% and 96.4%, respectively. In aneurysmal operations, with a 70% reduction in amplitude as the threshold for motor palsy, the sensitivity and specificity with CMAP compensation were 100% and 94.8%, respectively. Compensation by CMAP was especially useful in aneurysmal operations. In all neurosurgical operations, with a 70% reduction in amplitude as the threshold for motor palsy, the sensitivity and specificity with CMAP compensation were 95.0% and 90.9%, respectively.
Conclusions:Intraoperative TCMEP monitoring is a significantly reliable method for preventing postoperative motor palsy in both cranial and spinal surgery. A 70% reduction in the compensated amplitude is considered to be a suitable alarm point in all neurological operations.
Keywords: Cerebral aneurysm, compound muscle action potential, motor-evoked potential, spinal operation, transcranial stimulation
In recent neurosurgical operations, newly developed neurological deficits are not considered acceptable as a postoperative complication even in a lifesaving operation. To prevent such deficits, intraoperative neurophysiological monitoring has been widely applied in brain tumor operations, cerebrovascular disease operations, spinal operations, and microvascular decompression.[
For different types of operation, which should give an alarm in TCMEP monitoring, we examined the sensitivity and specificity at the alarm point, as well as the reliability and utility of TCMEP monitoring in neurosurgical operations.
Intraoperative TCMEP monitoring was performed in 342 neurosurgical operations from December 2001 to March 2011. In this report, we analyzed 283 neurosurgical operations with TCMEP compensated by compound muscle action potentials (CMAPs) after peripheral nerve stimulation documented bellow, for the patients without preoperative motor palsy, and accepted paralysis in the manual muscle test (MMT) of less than 3/5,[
Surface electrodes to apply stimulation for the compensation of MEP by CMAP after peripheral nerve stimulation were placed on the median nerve at the affected wrist. CMAP by single, bipolar supramaximum stimulation (20–50 mA), which had been determined at the beginning of the operation, on the median nerve at the affected wrist 2 sec after each transcranial stimulation of the motor area, was recorded in all operations.[
Postoperative motor function was judged at 1 week after operation. Our definition of motor palsy was less than 2/5 of the muscle strength by MMT at 1 week after the operation. False-negative results were diagnosed as motor palsy less than 2/5 of the muscle strength by MMT continuing more than a week without significant MEP amplitude decrease. False-positive results were diagnosed as motor function more than 2/5 of the muscle strength by MMT at a week after the operation with significant MEP amplitude decrease. Of course, motor function immediately after the operation had been certainly observed, but it was not statistically analyzed. Long-term outcome, exactly permanent motor function, was also not analyzed in our series.
For the analysis, we referred to a report by Langeloo et al. that an 80% reduction in amplitude was significant in spinal surgery.[
Overall, no adverse events were noted with high-voltage transcranial stimulations or electromyogram recordings. TCMEP could be recorded in all 283 operations. In cranial operations, TCMEP was performed immediately after artificial cerebrospinal fluid (CSF) infiltrated the operative field, since the amplitude had been reduced after CSF removal. Temporary amplitude reduction was also observed in patients with little cerebral cross-flow during temporary internal carotid artery occlusion in CEA or the use of a temporary clip in aneurysmal operations. Arterial stenosis due to clipping of the aneurysm and long-term cerebral compression by a retractor induced a reduction in the amplitude of TCMEP. In these cases, the amplitude was soon recovered by recanalization of the artery or a pause in the operative procedure. In spinal operations, a temporary disappearance or severe reduction in the amplitude of TCMEP immediately after decompression was observed in two lumbar spinal canal stenosis operations and two cervical spondylosis operations.
Sensitivity, specificity, and setting of the alarm point in transcranial motor-evoked potential
For each type of operation, sensitivities and specificities were calculated according to the amplitude reduction rate (30–100%, every 10%) with or without compensation by CMAP after peripheral nerve stimulation in 283 patients without preoperative motor palsy under MMT 3/5 [
Statistical analysis of intraoperative transcranial motor-evoked potential monitoring
Fisher's exact probability test was performed based on 2 × 2 tables of the results of 283 instances of TCMEP monitoring in patients without preoperative motor palsy (MMT < 3/5) according to the presence or absence of postoperative motor palsy, and the presence or absence of significant amplitude reduction (spinal and brain tumor, >80%; aneurysm andall, >70%) [
2 × 2 tables of the results of 283 instances of TCMEP monitoring in patients without preoperative motor palsy according to the presence or absence of postoperative motor palsy, and the presence or absence of significant amplitude reduction (spinal and brain tumor, >80%; aneurysm and other, >70%)
A 58-year-old woman was admitted with Wallenberg syndrome due to occlusion of the right posterior inferior cerebellar artery [
Case 1. A 58-year-old woman was admitted with Wallenberg syndrome due to occlusion of the right posterior inferior cerebellar artery (a). Her angiogram showed a basilar bifurcation aneurysm (b, c). Two months after the infarction, a craniotomy for neck clipping was performed. Her transcranial motor-evoked potential with 300-V stimulation disappeared with temporary occlusion of the basilar artery for 10 min (d, arrow) and partially recovered by recirculation after neck clipping (d, arrow head). Postoperatively, angiography after the operation showed complete neck occlusion (e, f)
A 47-year-old man had been struck by a motor vehicle while on his bicycle and suffered from motor weakness of his hands. The magnetic resonance image of his cervical spine showed marked spinal canal stenosis at C3-6 by spondylotic change [Figure
Case 2. A 47-year-old man had been struck by a motor vehicle while on his bicycle and suffered from motor weakness of his hands. The magnetic resonance image of his cervical spine showed marked spinal canal stenosis at C3-6 by spondylotic change (a–c). Right C3-6 unilateral open-door laminoplasty was performed a month after the trauma (d). Although full decompression was achieved (e), the amplitudes of transcranial motor-evoked potential decreased after decompression. The final amplitude reduction rates were 96% (left abductor pollicis brevis) and 89% (right abductor pollicis brevis) with compound muscle action potential compensation
Prior to the introduction of Propofol anesthesia, intraoperative monitoring by SEP had been used in neurosurgery.[
As noted previously, there are two ways to stimulate the motor cortex: direct cortical stimulation and transcranial stimulation. On the other hand, direct (D) waves can be obtained from epidural electrodes in the cervical spine as spinal cord-evoked potentials rather than being obtained with surface or needle electrodes as is usually done with EMG.[
MEP by direct motor area stimulation is highly sensitive and is widely used not only in operations for brain tumors adjacent to a motor area or pyramidal tract, but also in cerebrovascular operations, such as clipping of an aneurysm.[
We use CMAP after peripheral nerve stimulation for the compensation of MEP amplitude change only by muscle relaxants, not by anesthetics.[
In TCMEP, the stimulated site, body movement due to high-voltage stimulation, and the difficulty of judging changes in amplitude and latency have been reported to be controversial. The stimulated site has been reported to be the brain stem as calculated by the latency after extreme high-voltage (960 V) transcranial stimulation.[
The statistically significant changes in TCMEP amplitudes were consistent with the clinical outcomes in patients without preoperative motor palsy, and this clarified the clinical usefulness of TCMEP. With regard to the stimulated site of TCMEP, it is well known that temporary occlusion of the internal carotid artery or middle cerebral artery causes a reduction in the amplitude of TCMEP.[
The sensitivity and specificity of TCMEP vary according to the operation site because the stimulating site of transcranial stimulation is obvious. Alarm point should be set individually according to the operative site. Indeed, the transcranial stimulation might lead to preserve MEPs being caused by deep white matter stimulation, but it is not so important in spinal surgery. It is well known that in spine surgery, amplitude decrement does not result in permanent motor deficit and often results in transient motor deficits.[
There is little consensus regarding the evaluation of the amplitude change and alarm point in TCMEP.[
In our study, the specificity of TCMEP was 100% in brain tumor and aneurysmal operations, and the sensitivity was 100% in spinal surgery. The relatively low sensitivity of TCMEP in craniotomy seems to be caused by the stimulated site of TCMEP. Conversely, the specificity of TCMEP was relatively low in spinal surgery; TCMEP was too sensitive in spinal surgery. In actual practice, aggressive decompression of the spinal cord or root in laminoplasty often causes a sudden decrease in the amplitude of TCMEP probably due to reversible hyperemia. In these cases, if postoperative motor palsy did not occur, reversible dysfunction of the spinal cord or root may have already recovered immediately after the operation.
In conclusion, the present results show that TCMEP monitoring could predict postoperative motor palsy not only in spinal operations but also in craniotomy. The sensitivity and specificity of TCMEP were improved by compensation with CMAP after peripheral nerve stimulation. Since motor palsy newly develops postoperatively at an 80% reduction in amplitude in TCMEP for patients who do not have preoperative motor palsy, a 70% reduction in amplitude should be considered to be the alarm point of TCMEP.
1. Biebuyck JF. Propofol. An update on its clinical use. Anesthesiology. 1994. 81: 1005-43
2. Burke D, Hicks RG. Surgical monitoring of motor pathways. J Clin Neurophysiol. 1998. 15: 194-205
3. Daniels L, Worthingham C.editors. Muscle Testing: Techniques of manual examination. Philadelphia: WB Saunders Co; 1986. p.
4. Deletis V, Isgum V, Amassian VE. Neurophysiological mechanisms underlying motor-evoked potentials in anesthetized humans Part 1.Recovery time of corticospinal tract waves elicited by pairs of transcranial electrical stimulation. Clin Neurophysiol. 2001. 112: 438-44
5. Deletis V, Rodi Z, Amassian VE. Neurophysiological mechanisms underlying motor-evoked potentials in anesthetized humans. Part 2. Relationship between epidurally and muscle recorded MEPs in man. Clin Neurophysiol. 2001. 112: 445-52
6. Fujiki M, Furukawa Y, Kamida T, Anan M, Inoue R, Abe T. Intraoperative corticomuscular motor evoked potentials for evaluation of motor function: A comparison with corticospinal D and I waves. J Neurosurg. 2006. 104: 85-92
7. Iwasaki M, Kuroda S, Niiya Y, Ishikawa T, Iwasaki Y. Sensitivity of motor evoked potential (MEP) to intraoperative cerebral ischemia: Case report. Jpn J Neurosurg (Tokyo). 2008. 17: 622-6
8. Kaneko M, Fukamachi A, Sasaki H, Miyazawa N, Yagishita T, Nukui H. Intraoperative monitoring of the motor function: Experimental and clinical study. Acta Neurochir Suppl. 1988. 42: 18-21
9. Kombos T, Suess O, Ciklatekerlio O, Brock M. Monitoring of intraoperative motor evoked potentials to increase the safety of surgery in and around the motor cortex. J Neurosurg. 2001. 95: 608-14
10. Kombos T, Kopetsch O, Suess O, Brock M. Does preoperative paresis influence intraoperative monitoring of the motor cortex?. J Clin Neurophysiol. 2003. 20: 129-34
11. Langeloo DD, Lelivelt A, Louis Journëe H, Slappendel R, de Kleuver M. Transcranial electrical motor-evoked potential monitoring during surgery for spinal deformity: A study of 145 patients. Spine. 2003. 28: 1043-50
12. Lesser RP, Raudzens P, Luders H, Nuwer MR, Goldie WD, Morris HH. Postoperative neurological deficits may occur despite unchanged intraoperative somatosensory evoked potential. Ann Neurol. 1986. 19: 22-5
13. Levy WJ. Clinical experience with motor and cerebellar evoked potential monitoring. Neurosurgery. 1987. 20: 169-82
14. MacDonald DB. Safety of intraoperative transcranial electrical stimulation motor-evoked potential monitoring. J Clin Neurophysiol. 2002. 19: 416-29
15. McLellan DL. The electromyographic silent period produced by supramaximal electrical stimulation in normal man. J Neurol Neurosurg Psychiatry. 1973. 36: 334-41
16. Mochida K, Shinomiya K, Komori H, Furuya K. A new method of multisegment motor pathway monitoring using muscle potentials after train spinal stimulation. Spine. 1995. 20: 2240-6
17. Morota N, Deletis V, Constantini S, Kofler M, Cohen H, Epstein FJ. The role of motor evoked potentials during surgery for intramedullary spinal cord tumors. Neurosurgery. 1997. 41: 1327-36
18. Neuloh G, Schramm J. Monitoring of motor evoked potential compared with somatosensory evoked potentials and microvascular Doppler ultrasonography in cerebral aneurysm surgery. J Neurosurg. 2004. 100: 389-99
19. Neuloh G, Pechstein U, Schramm J. Motor tract monitoring during insular glioma surgery. J Neurosurg. 2007. 106: 582-92
20. Quinones-Hinojosa A, Lyon R, Zada G, Lamborn KR, Gupta N, Parsa AT. Changes in transcranial motor evoked potentials during intramedullary spinal cord tumor resection correlate with postoperative motor function. Neurosurgery. 2005. 56: 982-93
21. Rothwell J, Burke D, Hicks RG. Transcranial electrical stimulation of the motor cortex in man: Further evidence for the site of activation. J Physiol. 1994. 481: 243-50
22. Spielholz NI, Benjamin MV, Engler GL, Ransohoff J. Somatosensory evoked potentials during decompression and stabilization of the spine.Methods and findings. Spine. 1979. 4: 500-5
23. Suzuki K, Kodama N, Sasaki T, Matsumoto M, Konno Y, Sakuma J. Intraoperative monitoring of blood flow insufficiency in the anterior choroidal artery during aneurysm surgery. J Neurosurg. 2003. 98: 507-14
24. Szelenyi A, Bueno de Camargo A, Flamm E, Deletis V. Neurophysiological criteria for intraoperative prediction of pure motor hemiplegia during aneurysm surgery. Case report. J Neurosurg. 2003. 99: 575-8
25. Szelenyi A, Langer D, Kothbauer K, De Camargo AB, Flamm ES, Deletis V. Monitoring of muscle motor evoked potentials during cerebral aneurysm surgery: Intraoperative changes and postoperative outcome. J Neurosurg. 2006. 105: 675-81
26. Szelenyi A, Hattingen E, Weidauer S, Seifert V, Ziemann U. Intraoperative motor evoked potential alteration in intracranial tumor surgery and its relation to signal alteration in postoperative magnetic resonance imaging. Neurosurgery. 2010. 67: 302-13
27. Takanashi J, Tanaka S. Efficacy of transcranial high-voltage motor evoked potential as neurosurgical intraoperative monitoring. Jpn J Clin Neurophysiol. 2004. 32: 4-11
28. Tanaka S, Iwamoto K, Sagiuchi T, Takanashi J, Iwamoto K, Sato S. Efficacy of intraoperative transcranial motor evoked potential monitoring in cerebro-vascular disease. Surg Cerebral Stroke. 2004. 32: 431-6
29. Tanaka S, Kobayashi I, Sagiuchi T, Takanashi J, Iwamoto K, Sato S. Compensation of intraoperative transcranial motor-evoked potential monitoring by compound muscle action potential after peripheral nerve stimulation. J Clin Neurophysiol. 2005. 22: 271-4
30. Yamamoto T, Katayama Y, Fukaya S, Kurihara J, Kasai M, Maeda M. Comparison of the descending spinal cord evoked potentials with direct motor cortex stimulation and with transcranial brain stimulation. Clin Electroencephalogr. 1998. 40: 162-6
31. Yamamoto T, Katayama Y, Nagaoka T, Kobayashi K, Fukaya C. Intraoperative monitoring of the corticospinal motor evoked potential (D-wave): Clinical index for postoperative motor function and functional recovery. Neurol Med Chir (Tokyo). 2004. 44: 170-82
32. Zhou HH, Kelly PJ. Transcranial electrical motor-evoked potential monitoring for brain tumor resection. Neurosurgery. 2001. 48: 1075-81