Impact of anesthesia on transcranial electric motor evoked potential monitoring during spine surgery: a review of the literature

Anthony C. Wang M.D., Khoi D. Than M.D., Arnold B. Etame M.D., Frank La Marca M.D., and Paul Park M.D.
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  • Department of Neurosurgery, University of Michigan Health System, Ann Arbor, Michigan
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Object

Transcranial motor evoked potential (TcMEP) monitoring is frequently used in complex spinal surgeries to prevent neurological injury. Anesthesia, however, can significantly affect the reliability of TcMEP monitoring. Understanding the impact of various anesthetic agents on neurophysiological monitoring is therefore essential.

Methods

A literature search of the National Library of Medicine database was conducted to identify articles pertaining to anesthesia and TcMEP monitoring during spine surgery. Twenty studies were selected and reviewed.

Results

Inhalational anesthetics and neuromuscular blockade have been shown to limit the ability of TcMEP monitoring to detect significant changes. Hypothermia can also negatively affect monitoring. Opioids, however, have little influence on TcMEPs. Total intravenous anesthesia regimens can minimize the need for inhalational anesthetics.

Conclusions

In general, selecting the appropriate anesthetic regimen with maintenance of a stable concentration of inhalational or intravenous anesthetics optimizes TcMEP monitoring.

Abbreviations used in this paper: MAC = minimal anesthetic concentration; MEP = motor evoked potential; TcMEP = transcranial MEP; TIVA = total intravenous anesthesia.

Object

Transcranial motor evoked potential (TcMEP) monitoring is frequently used in complex spinal surgeries to prevent neurological injury. Anesthesia, however, can significantly affect the reliability of TcMEP monitoring. Understanding the impact of various anesthetic agents on neurophysiological monitoring is therefore essential.

Methods

A literature search of the National Library of Medicine database was conducted to identify articles pertaining to anesthesia and TcMEP monitoring during spine surgery. Twenty studies were selected and reviewed.

Results

Inhalational anesthetics and neuromuscular blockade have been shown to limit the ability of TcMEP monitoring to detect significant changes. Hypothermia can also negatively affect monitoring. Opioids, however, have little influence on TcMEPs. Total intravenous anesthesia regimens can minimize the need for inhalational anesthetics.

Conclusions

In general, selecting the appropriate anesthetic regimen with maintenance of a stable concentration of inhalational or intravenous anesthetics optimizes TcMEP monitoring.

Abbreviations used in this paper: MAC = minimal anesthetic concentration; MEP = motor evoked potential; TcMEP = transcranial MEP; TIVA = total intravenous anesthesia.

Multimodal neurophysiological monitoring is commonly used in complex spine surgeries for prevention of intraoperative neurological injury. In 1980, Merton and Morton20 introduced a novel technique for intraoperative neurophysiological monitoring of spinal cord integrity by using MEP monitoring, which has since become the standard for intraoperative monitoring. This was initially accomplished by stimulating the motor cortex transcranially, and recording the subsequent evoked action potentials in peripheral muscles. Monitoring of the motor tracts allowed real-time assessment of the integrity of the descending pyramidal tracts. Importantly, monitoring of the motor pathways included portions of the spinal cord supplied by the anterior spinal artery. Compromise of this vascular distribution largely spares the dorsal columns, which is the dominant substrate for somatosensory evoked potential monitoring.

Variations of the transcranial method of stimulation followed, including stimulation of the spinal cord, skull, hard palate, and exposed motor cortex.26 Transcranial magnetic stimulation of MEPs was successfully accomplished as well, but it is an impractical method, given the complex electromagnetic environment within the operating room and the ease of electrical stimulation.8

Early attempts at MEP monitoring encountered similar difficulties, with signal suppression due to anesthesia. Inghilleri et al.11 first reported improved monitoring with paired stimulation, which is attributed to effective accumulation of excitatory postsynaptic potentials at the level of the anterior horn motor neurons. Application of a short train of stimulation, spaced 2–5 msec apart, was found to improve greatly the reliability of MEP monitoring.6,16,27 Later, the application of a 2- to 5-second tetanic stimulation to the peripheral muscles ~ 1–5 seconds prior to TcMEP stimulation could effectively augment MEP monitoring.14

Presently, TcMEPs are commonly used in complex spinal operations, including tumor and deformity surgery. Given that neurophysiological monitoring can be significantly influenced by anesthesia, awareness of how various anesthetic agents can impact TcMEPs is essential.

Methods

An extensive search of the US National Library of Medicine database was performed using the terms “anesthesia,” “neurophysiology,” “electrophysiology,” “motor evoked potential,” “monitoring,” and “spine surgery.” Retrieved articles were screened for human patients undergoing spine surgery in which electric TcMEP monitoring was used. Case reports and small studies of < 5 patients were excluded. From among the 50 articles initially identified, we selected 20 articles in which the effect of anesthetic agents on TcMEP monitoring was studied.

Results and Discussion

Transcranial MEP recording, when used as a part of multimodality intraoperative neurophysiological monitoring, is exquisitely sensitive in recognizing intraoperative nervous injury, both by mechanical and by ischemic mechanisms.10 However, MEP recordings are also known to be affected by a number of anesthetic agents, due to the inhibitory effect of inhalational anesthetics at the cortical axon synapses and spinal anterior horn cells. At the time of Merton and Morton's experiments,20 halogenated anesthetics and nitrous oxide were commonly used in spine surgeries. The tendency of these anesthetics to depress motor neuron activity was quickly discovered, and intravenous anesthesia was introduced, initially using fentanyl and propofol, to mitigate this effect.12

The successful performance of intraoperative neurophysiological monitoring is dependent on careful maintenance of a steady and consistent electrophysiological baseline. The anesthetic regimens used in spine surgeries involving the use of intraoperative MEP monitoring have since been studied in great detail. Relevant clinical studies are listed in Table 1. All volatile halogenated anesthetics, as well as nitrous oxide, produce a dose-dependent reduction in MEP signal amplitude. Because the signal amplitudes of MEP recordings are already quite small, the effect of these inhalational agents can limit the practitioner's ability to detect significant changes intraoperatively. A number of studies have shown that with partial neuromuscular blockade, effective monitoring could still be performed at 0.5 MAC, with more variability at 1.0 MAC.3 With other, less disruptive options available, inhalational agents are generally to be avoided in cases requiring neurophysiological monitoring.

TABLE 1:

Literature review of clinical studies reporting the effect of anesthetic regimens used in spine surgeries involving intraoperative MEP monitoring

Authors & YearNo. of PatientsAnesthetic Agents UsedResults
Zentner et al., 198915nitrous oxide, fentanyl, flunitrazepam, thiopentalnitrous oxide decreased electric TcMEP amplitudes, whereas fentanyl, flunitrazepam, & thiopental had only a minor effect on TcMEP
Calancie et al., 19918isofluraneaddition of isoflurane resulted in marked attenuation of electric TcMEP responses
Jellinek et al.,12 199134propofolalthough propofol anesthesia caused reduction in magnetic TcMEP amplitude, intraop monitoring was sensitive to disturbance in motor pathways
Jellinek et al.,13 199134nitrous oxide & propofolw/ concentrations < 50%, nitrous oxide can be used w/o significant negative effect on electric TcMEPs in patients under propofol anesthesia
Kalkman et al., 199211vecuroniumelectric TcMEP monitoring is possible w/ partial neuromuscular blockade
Taniguchi et al., 199377propofol, etomidate, methohexital, or thiopentalall 4 intravenous anesthetic agents shown to have negative influence on magnetic TcMEP monitoring
Woodforth et al., 19966isoflurane & nitrous oxidesatisfactory electric TcMEPs could be obtained w/ nitrous oxide & isoflurane (0.1%–0 for 10 min); isoflurane concentrations > 0.1% resulted in loss of responses
Ubags et al., 199718etomidate or ketamine + sufentanil + nitrous oxideetomidate or ketamine can be used to supplement nitrous oxide/opioid anesthesia w/o significant impact on electric TcMEP monitoring
Ubags et al., 199810isofluraneisoflurane significantly depresses single-stimulus electric TcMEPs, but multi-stimulus TcMEPs can allow monitoring up to 1 MAC of isoflurane w/ nitrous oxide/opioid anesthesia
Kawaguchi et al., 200058nitrous oxide–fentanyl-ketamine w/ or w/o low-dose (1–3 mg/kg/hr) propofolpropofol negatively affects single-stimulus electric TcMEPs, but train of stimuli for TcMEPs allows use of low-dose propofol to supplement ketamine-based anesthesia
Pelosi et al., 200150propofol & nitrous oxide vs isoflurane & nitrous oxidemultipulse electric TcMEP monitoring possible in 97% of spinal ops w/ propofol, nitrous oxide, & opioid anesthesia; only 61% could be monitored w/ isoflurane, nitrous, & opioid anesthesia
Scheufler & Zentner, 200240alfentanil, sufentanil, fentanyl, remifentanil, thiopental, midazolam, etomidate, ketamine, & propofolTIVA using remifentanil & midazolam (or propofol) allows satisfactory monitoring of magnetic TcMEPs; etomidate & midazolam had minimal effect on TcMEPs; ketamine had a suppressive influence at high doses
Nathan et al., 200315propofolmultipulse electric TcMEPs were reduced in a dose-dependent manner, although latencies were unchanged w/ propofol; combining propofol w/ remifentanil can allow adequate monitoring
Chen, 200435isoflurane vs propofolintravenous anesthesia w/ propofol allowed adequate monitoring in all patients by using multipulse electric TcMEPs; only 58.8% of patients could be monitored when isoflurane anesthesia was used
Lo et al., 200410desfluranecombination of nitrous oxide & desflurane (0.5% maximum alveolar concentration) allowed adequate monitoring using multipulse electric TcMEPs
Lo et al., 200620desflurane vs TIVAboth anesthetic regimens (desflurane w/ nitrous oxide & TIVA w/ propofol) allowed adequate monitoring w/ multipulse electric TcMEPs
Zaarour et al., 200734ketamine added to TIVA (propofol & remifentanil)addition of low-dose ketamine did not limit the voltage necessary to obtain maximal amplitude responses w/ electric TcMEPs
Anschel et al., 200818dexmedetomidine added to TIVAdexmedetomidine can be used as an adjunct to TIVA w/o significantly impacting TcMEP monitoring
Tobias et al., 20089dexmedetomidine added to TIVA (propofol & remifentanil)w/ adjustment of propofol dosing, dexmedetomidine can be added as a supplement to the anesthetic regimen w/o significantly influencing electric TcMEP monitoring
Hayashi et al., 200935sevofluranesevoflurane suppressed TcMEP monitoring; no significant difference between conventional & posttetanic MEP monitoring observed

With the relative ease of TIVA administration, the need for inhalational anesthetics can be minimized. Various combinations of intravenous anesthetic regimens have been described and tested intraoperatively. Propofol, synthetic narcotics, and N-methyl-d-aspartate receptor antagonists have been used successfully in sizable series of spine operations, as detailed in Table 1. Although propofol does demonstrate a dose-dependent reduction in MEP amplitude without effect on latency,12 it has repeatedly been shown to produce a more stable neurophysiological environment for monitoring, when compared with inhalational anesthetics.21–24

Opioids have shown minimal influence on MEP recording, and administered as a continuous infusion, are an invaluable part of an anesthetic regimen for spine surgery requiring neurophysiological monitoring. More recently, interest has been shown in using ketamine and dexmedetomidine as part of a TIVA regimen. Ketamine is known to enhance the monitoring of evoked potentials,7 and has demonstrated its utility in a number of studies.24,29,32 Dexmedetomidine has been used as a supplement to TIVA to reduce the dose of propofol, without evidence of detriment.2,28 Neuromuscular blockade is known to suppress MEP signal recording. Partial paralysis has been used on rare occasions, but is generally too unpredictable to use regularly.1

Electric conduction increases in velocity with temperature, and the same principle appears to apply in MEP monitoring. Hypothermia is thought to decrease the reliability of MEP monitoring, demonstrating an increase in stimulation threshold with decreasing temperatures.25 Similarly, latency is reduced and conduction velocity increased with hyperthermia, although MEPs deteriorate above 42°C (Table 2).

TABLE 2:

Key points regarding the impact of anesthesia on TcMEP monitoring

inhalational halogenated anesthetics & nitrous oxide lead to a dose-dependent reduction in MEP signal amplitude, limiting the ability to detect significant neurological changes
use of TIVA can minimize the need for halogenated anesthetics
TIVA regimens can include a combination of propofol, synthetic narcotics, & N-methyl-d-aspartate receptor antagonists (that is, ketamine)
neuromuscular blockade & hypothermia also suppress MEP recording
opioids have minimal impact on MEP recording
regardless of regimen used, it is crucial to maintain a stable concentration of the inhalational or intravenous anesthetic, because sudden changes in dosage can cause MEP changes, making interpretation difficult

Conclusions

Overall, intraoperative neurophysiological monitoring has been shown to offer excellent reliability in assessing iatrogenic neurological injury. Selection of the appropriate anesthetic regimen can help to optimize the data recorded. Regardless of the regimen used, it is of utmost importance to maintain a stable concentration of inhalational or intravenous anesthetic. Although improvements in monitoring technology have compensated for inherently low signal amplitudes that are made more difficult by the nature of anesthesia, sudden changes in dose can induce MEP changes, making interpretation impossible.

Disclaimer

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

References

  • 1

    Adams DC, , Emerson RG, , Heyer EJ, , McCormick PC, , Carmel PW, & Stein BM, : Monitoring of intraoperative motorevoked potentials under conditions of controlled neuromuscular blockade. Anesth Analg 77:913918, 1993

    • Search Google Scholar
    • Export Citation
  • 2

    Anschel DJ, , Aherne A, , Soto RG, , Carrion W, , Hoegerl C, & Nori P, : Successful intraoperative spinal cord monitoring during scoliosis surgery using a total intravenous anesthetic regimen including dexmedetomidine. J Clin Neurophysiol 25:5661, 2008

    • Search Google Scholar
    • Export Citation
  • 3

    Bernard JM, , Pereon Y, , Fayet G, & Guiheneuc P: Effects of isoflurane and desflurane on neurogenic motor- and somatosensory-evoked potential monitoring for scoliosis surgery. Anesthesiology 85:10131019, 1996

    • Search Google Scholar
    • Export Citation
  • 4

    Calancie B, , Klose KJ, , Baier S, & Green BA: Isoflurane-induced attenuation of motor evoked potentials caused by electrical motor cortex stimulation during surgery. J Neurosurg 74:897904, 1991

    • Search Google Scholar
    • Export Citation
  • 5

    Chen Z: The effects of isoflurane and propofol on intraoperative neurophysiological monitoring during spinal surgery. J Clin Monit Comput 18:303308, 2004

    • Search Google Scholar
    • Export Citation
  • 6

    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 112:445452, 2001

    • Search Google Scholar
    • Export Citation
  • 7

    Erb TO, , Ryhult SE, , Duitmann E, , Hasler C, , Luetschg J, & Frei FJ: Improvement of motor-evoked potentials by ketamine and spatial facilitation during spinal surgery in a young child. Anesth Analg 100:16341636, 2005

    • Search Google Scholar
    • Export Citation
  • 8

    Gugino LD, , Aglio LS, , Segal ME, , Gonzalez AA, & Kraus KH: Use of transcranial magnetic stimulation for monitoring spinal cord motor pathways. Sem Spinal Surg 9:315336, 1997

    • Search Google Scholar
    • Export Citation
  • 9

    Hayashi H, , Kawaguchi M, , Abe R, , Yamamoto Y, , Inoue S, & Koizumi M, : Evaluation of the applicability of sevoflurane during post-tetanic myogenic motor evoked potential monitoring in patients undergoing spinal surgery. J Anesth 23:175181, 2009

    • Search Google Scholar
    • Export Citation
  • 10

    Hilibrand AS, , Schwartz DM, , Sethuraman V, , Vaccaro AR, & Albert TJ: Comparison of transcranial electric motor and somatosensory evoked potential monitoring during cervical spine surgery. J Bone Joint Surg Am 86-A:12481253, 2004

    • Search Google Scholar
    • Export Citation
  • 11

    Inghilleri M, , Berardelli A, , Cruccu G, , Priori A, & Manfredi M: Motor potentials evoked by paired cortical stimuli. Electroencephalogr Clin Neurophysiol 77:382389, 1990

    • Search Google Scholar
    • Export Citation
  • 12

    Jellinek D, , Jewkes D, & Symon L: Noninvasive intraoperative monitoring of motor evoked potentials under propofol anesthesia: effects of spinal surgery on the amplitude and latency of motor evoked potentials. Neurosurgery 29:551557, 1991

    • Search Google Scholar
    • Export Citation
  • 13

    Jellinek D, , Platt M, , Jewkes D, & Symon L: Effects of nitrous oxide on motor evoked potentials recorded from skeletal muscle in patients under total anesthesia with intravenously administered propofol. Neurosurgery 29:558562, 1991

    • Search Google Scholar
    • Export Citation
  • 14

    Kakimoto M, , Kawaguchi M, , Yamamoto Y, , Inoue S, , Horiuchi T, & Nakase H, : Tetanic stimulation of the peripheral nerve before transcranial electrical stimulation can enlarge amplitudes of myogenic motor evoked potentials during general anesthesia with neuromuscular blockade. Anesthesiology 102:733738, 2005

    • Search Google Scholar
    • Export Citation
  • 15

    Kalkman CJ, , Drummond JC, , Kennelly NA, , Patel PM, & Partridge BL: Intraoperative monitoring of tibialis anterior muscle motor evoked responses to transcranial electrical stimulation during partial neuromuscular blockade. Anesth Analg 75:584589, 1992

    • Search Google Scholar
    • Export Citation
  • 16

    Kalkman CJ, , Ubags LH, , Been HD, , Swaan A, & Drummond JC: Improved amplitude of myogenic motor evoked responses after paired transcranial electrical stimulation during sufentanil/ nitrous oxide anesthesia. Anesthesiology 83:270276, 1995

    • Search Google Scholar
    • Export Citation
  • 17

    Kawaguchi M, , Sakamoto T, , Inoue S, , Kakimoto M, , Furuya H, & Morimoto T, : Low dose propofol as a supplement to ketamine-based anesthesia during intraoperative monitoring of motor-evoked potentials. Spine 25:974979, 2000

    • Search Google Scholar
    • Export Citation
  • 18

    Lo YL, , Dan YF, , Tan YE, , Nurjannah S, , Tan SB, & Tan CT, : Intra-operative monitoring in scoliosis surgery with multipulse cortical stimuli and desflurane anesthesia. Spinal Cord 42:342345, 2004

    • Search Google Scholar
    • Export Citation
  • 19

    Lo YL, , Dan YF, , Tan YE, , Nurjannah S, , Tan SB, & Tan CT, : Intraoperative motor-evoked potential monitoring in scoliosis surgery: comparison of desflurane/nitrous oxide with propofol total intravenous anesthetic regimens. J Neurosurg Anesthesiol 18:211214, 2006

    • Search Google Scholar
    • Export Citation
  • 20

    Merton PA, & Morton HB: Stimulation of the cerebral cortex in the intact human subject. Nature 285:227, 1980

  • 21

    Nathan N, , Tabaraud F, , Lacroix F, , Moulies D, , Viviand X, & Lansade A, : Influence of propofol concentrations on multipulse transcranial motor evoked potentials. Br J Anaesth 91:493497, 2003

    • Search Google Scholar
    • Export Citation
  • 22

    Pechstein U, , Nadstawek J, , Zentner J, & Schramm J: Isoflurane plus nitrous oxide versus propofol for recording of motor evoked potentials after high frequency repetitive electrical stimulation. Electroencephalogr Clin Neurophysiol 108:175181, 1998

    • Search Google Scholar
    • Export Citation
  • 23

    Pelosi L, , Stevenson M, , Hobbs GJ, , Jardine A, & Webb JK: Intraoperative motor evoked potentials to transcranial electrical stimulation during two anaesthetic regimens. Clin Neurophysiol 112:10761087, 2001

    • Search Google Scholar
    • Export Citation
  • 24

    Scheufler KM, & Zentner J: Total intravenous anesthesia for intraoperative monitoring of the motor pathways: an integral view combining clinical and experimental data. J Neurosurg 96:571579, 2002

    • Search Google Scholar
    • Export Citation
  • 25

    Seyal M, & Mull B: Mechanisms of signal change during intraoperative somatosensory evoked potential monitoring of the spinal cord. J Clin Neurophysiol 19:409415, 2002

    • Search Google Scholar
    • Export Citation
  • 26

    Tamaki T, & Kubota S: History of the development of intraoperative spinal cord monitoring. Eur Spine J 16:Suppl 2 S140S146, 2007

  • 27

    Taniguchi M, , Cedzich C, & Schramm J: Modification of cortical stimulation for motor evoked potentials under general anesthesia: technical description. Neurosurgery 32:219226, 1993

    • Search Google Scholar
    • Export Citation
  • 28

    Tobias JD, , Goble TJ, , Bates G, , Anderson JT, & Hoernschemeyer DG: Effects of dexmedetomidine on intraoperative motor and somatosensory evoked potential monitoring during spinal surgery in adolescents. Paediatr Anaesth 18:10821088, 2008

    • Search Google Scholar
    • Export Citation
  • 29

    Ubags LH, , Kalkman CJ, & Been HD: Influence of isoflurane on myogenic motor evoked potentials to single and multiple transcranial stimuli during nitrous oxide/opioid anesthesia. Neurosurgery 43:9095, 1998

    • Search Google Scholar
    • Export Citation
  • 30

    Ubags LH, , Kalkman CJ, , Been HD, , Porsius M, & Drummond JC: The use of ketamine or etomidate to supplement sufentanil/ N2O anesthesia does not disrupt monitoring of myogenic transcranial motor evoked responses. J Neurosurg Anesthesiol 9:228233, 1997

    • Search Google Scholar
    • Export Citation
  • 31

    Woodforth IJ, , Hicks RG, , Crawford MR, , Stephen JP, & Burke DJ: Variability of motor-evoked potentials recorded during nitrous oxide anesthesia from the tibialis anterior muscle after transcranial electrical stimulation. Anesth Analg 82:744749, 1996

    • Search Google Scholar
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  • 32

    Zaarour C, , Engelhardt T, , Strantzas S, , Pehora C, , Lewis S, & Crawford MW: Effect of low-dose ketamine on voltage requirement for transcranial electrical motor evoked potentials in children. Spine 32:E627E630, 2007

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  • 33

    Zentner J, , Kiss I, & Ebner A: Influence of anesthetics—nitrous oxide in particular—on electromyographic response evoked by transcranial electrical stimulation of the cortex. Neurosurgery 24:253256, 1989

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Contributor Notes

Address correspondence to: Paul Park, M.D., Department of Neurosurgery, University of Michigan Health System, 1500 East Medical Center Drive, Room 3552, Taubman Center, Ann Arbor, Michigan 48109-5338. email:ppark@umich.edu.
  • 1

    Adams DC, , Emerson RG, , Heyer EJ, , McCormick PC, , Carmel PW, & Stein BM, : Monitoring of intraoperative motorevoked potentials under conditions of controlled neuromuscular blockade. Anesth Analg 77:913918, 1993

    • Search Google Scholar
    • Export Citation
  • 2

    Anschel DJ, , Aherne A, , Soto RG, , Carrion W, , Hoegerl C, & Nori P, : Successful intraoperative spinal cord monitoring during scoliosis surgery using a total intravenous anesthetic regimen including dexmedetomidine. J Clin Neurophysiol 25:5661, 2008

    • Search Google Scholar
    • Export Citation
  • 3

    Bernard JM, , Pereon Y, , Fayet G, & Guiheneuc P: Effects of isoflurane and desflurane on neurogenic motor- and somatosensory-evoked potential monitoring for scoliosis surgery. Anesthesiology 85:10131019, 1996

    • Search Google Scholar
    • Export Citation
  • 4

    Calancie B, , Klose KJ, , Baier S, & Green BA: Isoflurane-induced attenuation of motor evoked potentials caused by electrical motor cortex stimulation during surgery. J Neurosurg 74:897904, 1991

    • Search Google Scholar
    • Export Citation
  • 5

    Chen Z: The effects of isoflurane and propofol on intraoperative neurophysiological monitoring during spinal surgery. J Clin Monit Comput 18:303308, 2004

    • Search Google Scholar
    • Export Citation
  • 6

    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 112:445452, 2001

    • Search Google Scholar
    • Export Citation
  • 7

    Erb TO, , Ryhult SE, , Duitmann E, , Hasler C, , Luetschg J, & Frei FJ: Improvement of motor-evoked potentials by ketamine and spatial facilitation during spinal surgery in a young child. Anesth Analg 100:16341636, 2005

    • Search Google Scholar
    • Export Citation
  • 8

    Gugino LD, , Aglio LS, , Segal ME, , Gonzalez AA, & Kraus KH: Use of transcranial magnetic stimulation for monitoring spinal cord motor pathways. Sem Spinal Surg 9:315336, 1997

    • Search Google Scholar
    • Export Citation
  • 9

    Hayashi H, , Kawaguchi M, , Abe R, , Yamamoto Y, , Inoue S, & Koizumi M, : Evaluation of the applicability of sevoflurane during post-tetanic myogenic motor evoked potential monitoring in patients undergoing spinal surgery. J Anesth 23:175181, 2009

    • Search Google Scholar
    • Export Citation
  • 10

    Hilibrand AS, , Schwartz DM, , Sethuraman V, , Vaccaro AR, & Albert TJ: Comparison of transcranial electric motor and somatosensory evoked potential monitoring during cervical spine surgery. J Bone Joint Surg Am 86-A:12481253, 2004

    • Search Google Scholar
    • Export Citation
  • 11

    Inghilleri M, , Berardelli A, , Cruccu G, , Priori A, & Manfredi M: Motor potentials evoked by paired cortical stimuli. Electroencephalogr Clin Neurophysiol 77:382389, 1990

    • Search Google Scholar
    • Export Citation
  • 12

    Jellinek D, , Jewkes D, & Symon L: Noninvasive intraoperative monitoring of motor evoked potentials under propofol anesthesia: effects of spinal surgery on the amplitude and latency of motor evoked potentials. Neurosurgery 29:551557, 1991

    • Search Google Scholar
    • Export Citation
  • 13

    Jellinek D, , Platt M, , Jewkes D, & Symon L: Effects of nitrous oxide on motor evoked potentials recorded from skeletal muscle in patients under total anesthesia with intravenously administered propofol. Neurosurgery 29:558562, 1991

    • Search Google Scholar
    • Export Citation
  • 14

    Kakimoto M, , Kawaguchi M, , Yamamoto Y, , Inoue S, , Horiuchi T, & Nakase H, : Tetanic stimulation of the peripheral nerve before transcranial electrical stimulation can enlarge amplitudes of myogenic motor evoked potentials during general anesthesia with neuromuscular blockade. Anesthesiology 102:733738, 2005

    • Search Google Scholar
    • Export Citation
  • 15

    Kalkman CJ, , Drummond JC, , Kennelly NA, , Patel PM, & Partridge BL: Intraoperative monitoring of tibialis anterior muscle motor evoked responses to transcranial electrical stimulation during partial neuromuscular blockade. Anesth Analg 75:584589, 1992

    • Search Google Scholar
    • Export Citation
  • 16

    Kalkman CJ, , Ubags LH, , Been HD, , Swaan A, & Drummond JC: Improved amplitude of myogenic motor evoked responses after paired transcranial electrical stimulation during sufentanil/ nitrous oxide anesthesia. Anesthesiology 83:270276, 1995

    • Search Google Scholar
    • Export Citation
  • 17

    Kawaguchi M, , Sakamoto T, , Inoue S, , Kakimoto M, , Furuya H, & Morimoto T, : Low dose propofol as a supplement to ketamine-based anesthesia during intraoperative monitoring of motor-evoked potentials. Spine 25:974979, 2000

    • Search Google Scholar
    • Export Citation
  • 18

    Lo YL, , Dan YF, , Tan YE, , Nurjannah S, , Tan SB, & Tan CT, : Intra-operative monitoring in scoliosis surgery with multipulse cortical stimuli and desflurane anesthesia. Spinal Cord 42:342345, 2004

    • Search Google Scholar
    • Export Citation
  • 19

    Lo YL, , Dan YF, , Tan YE, , Nurjannah S, , Tan SB, & Tan CT, : Intraoperative motor-evoked potential monitoring in scoliosis surgery: comparison of desflurane/nitrous oxide with propofol total intravenous anesthetic regimens. J Neurosurg Anesthesiol 18:211214, 2006

    • Search Google Scholar
    • Export Citation
  • 20

    Merton PA, & Morton HB: Stimulation of the cerebral cortex in the intact human subject. Nature 285:227, 1980

  • 21

    Nathan N, , Tabaraud F, , Lacroix F, , Moulies D, , Viviand X, & Lansade A, : Influence of propofol concentrations on multipulse transcranial motor evoked potentials. Br J Anaesth 91:493497, 2003

    • Search Google Scholar
    • Export Citation
  • 22

    Pechstein U, , Nadstawek J, , Zentner J, & Schramm J: Isoflurane plus nitrous oxide versus propofol for recording of motor evoked potentials after high frequency repetitive electrical stimulation. Electroencephalogr Clin Neurophysiol 108:175181, 1998

    • Search Google Scholar
    • Export Citation
  • 23

    Pelosi L, , Stevenson M, , Hobbs GJ, , Jardine A, & Webb JK: Intraoperative motor evoked potentials to transcranial electrical stimulation during two anaesthetic regimens. Clin Neurophysiol 112:10761087, 2001

    • Search Google Scholar
    • Export Citation
  • 24

    Scheufler KM, & Zentner J: Total intravenous anesthesia for intraoperative monitoring of the motor pathways: an integral view combining clinical and experimental data. J Neurosurg 96:571579, 2002

    • Search Google Scholar
    • Export Citation
  • 25

    Seyal M, & Mull B: Mechanisms of signal change during intraoperative somatosensory evoked potential monitoring of the spinal cord. J Clin Neurophysiol 19:409415, 2002

    • Search Google Scholar
    • Export Citation
  • 26

    Tamaki T, & Kubota S: History of the development of intraoperative spinal cord monitoring. Eur Spine J 16:Suppl 2 S140S146, 2007

  • 27

    Taniguchi M, , Cedzich C, & Schramm J: Modification of cortical stimulation for motor evoked potentials under general anesthesia: technical description. Neurosurgery 32:219226, 1993

    • Search Google Scholar
    • Export Citation
  • 28

    Tobias JD, , Goble TJ, , Bates G, , Anderson JT, & Hoernschemeyer DG: Effects of dexmedetomidine on intraoperative motor and somatosensory evoked potential monitoring during spinal surgery in adolescents. Paediatr Anaesth 18:10821088, 2008

    • Search Google Scholar
    • Export Citation
  • 29

    Ubags LH, , Kalkman CJ, & Been HD: Influence of isoflurane on myogenic motor evoked potentials to single and multiple transcranial stimuli during nitrous oxide/opioid anesthesia. Neurosurgery 43:9095, 1998

    • Search Google Scholar
    • Export Citation
  • 30

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