Intraoperative Monitoring of Motor Function by Magnetic Motor Evoked Potentials

✓ The feasibility of high-frequency transcranial electrical stimulation (TES) through screw electrodes placed in the skull was investigated for use in intraoperative monitoring of the motor pathways in patients who are in a state of general anesthesia during cerebral and spinal operations. Motor evoked potentials (MEPs) were elicited by TES with a train of five square-wave pulses (duration 400 µsec, intensity ≤ 200 mA, frequency 500 Hz) delivered through metal screw electrodes placed in the outer table of the skull over the primary motor cortex in 42 patients. Myogenic MEPs to anodal stimulation were recorded from the abductor pollicis brevis (APB) and tibialis anterior (TA) muscles. The mean threshold stimulation intensity was 48 ± 17 mA for the APB muscles, and 112 ± 35 mA for the TA muscles. The electrodes were firmly fixed at the site and were not dislodged by surgical manipulation throughout the operation. No adverse reactions attributable to the TES were observed. Passing current through the screw electrodes stimulates the motor cortex more effectively than conventional methods of TES. The method is safe and inexpensive, and it is convenient for intraoperative monitoring of motor pathways.

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Intraoperative monitoring of motor evoked potentials: A review of 116 cases

Neurology ◽

10.1212/wnl.47.4.999 ◽

1996 ◽

Vol 47 (4) ◽

pp. 999-1004 ◽

Cited By ~ 68

Author(s):

K. J. Nagle ◽

R. G. Emerson ◽

D. C. Adams ◽

E. J. Heyer ◽

D. P. Roye ◽

...

Keyword(s):

Evoked Potentials ◽

Intraoperative Monitoring ◽

Motor Evoked Potentials

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Intraoperative corticomuscular motor evoked potentials for evaluation of motor function: a comparison with corticospinal D and I waves

Journal of Neurosurgery ◽

10.3171/jns.2006.104.1.85 ◽

2006 ◽

Vol 104 (1) ◽

pp. 85-92 ◽

Cited By ~ 40

Author(s):

Minoru Fujiki ◽

Yoshie Furukawa ◽

Tohru Kamida ◽

Mitsuhiro Anan ◽

Ryo Inoue ◽

...

Keyword(s):

Evoked Potentials ◽

Motor Function ◽

Wave Amplitude ◽

Motor Evoked Potentials ◽

Motor Dysfunction ◽

Cortical Gray Matter ◽

Group A ◽

Group B ◽

Group D ◽

D Wave

Object The goal of this study was to compare motor evoked potentials recorded from muscles (muscle MEPs or corticomuscular MEPs) with corticospinal MEPs recorded from the cervical epidural space (spinal MEPs or corticospinal MEPs) to assess their efficacy in the intraoperative monitoring of motor function. Methods Muscle and spinal MEPs were simultaneously recorded during surgery in 80 patients harboring brain tumors. Each case was assigned to one of four groups according to final changes in the MEPs: 1) Group A, in which there was an increased amplitude in the muscle MEP with an increased I3 wave amplitude (12 cases); 2) Group B, in which there was no significant change in the MEP (43 cases); 3) Group C, in which there was a decreased muscle MEP amplitude (< 35% of the control) with a decreased I wave amplitude but an unchanged D wave (15 cases); or 4) Group D, in which there was an absent muscle MEP with a decreased D wave amplitude (10 cases). In patients in Group A, the increase in the amplitude of the muscle MEP (range of increase 128–280%, mean increase 188.75 ± 48.79%) was well correlated with the increase in the I3 wave in corticospinal MEPs. Most of these patterns were observed in patients harboring meningiomas (10 [83.3%] of 12 cases). Patients in Group B displayed no changes in muscle and corticospinal MEPs and no signs of postoperative neurological deterioration. Patients in Group C showed a substantial decrease in the amplitude of the muscle MEP (range of decrease 5.3–34.8% based on the control waveform, mean change 21.81 ± 10.93%) without deterioration in the corticospinal D wave, and exhibited severe immediate postoperative motor dysfunction. This indicates dysfunction of the cortical gray matter, including the motor cortices, which are supposed to generate I waves. Patients in Group D exhibited decreases in the corticospinal D wave (range of decrease 21.5–55%, mean decrease 39.75 ± 11.45%) and an immediate cessation of the muscle MEP as well as severe permanent motor paresis. Conclusions These results indicate that, during surgery, monitoring of corticomuscular MEPs (which are related to I waves) is a much more sensitive method for the detection of immediate motor cortical damage than monitoring of corticospinal MEPs (D wave).

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Prognostic value of motor evoked potentials in motor function recovery of upper limb after stroke

Journal of Rehabilitation Medicine ◽

10.2340/16501977-0389 ◽

2009 ◽

Vol 41 (8) ◽

pp. 654-660 ◽

Cited By ~ 24

Author(s):

A Pizzi ◽

R Carrai ◽

C Falsini ◽

M Martini ◽

S Verdesca ◽

...

Keyword(s):

Evoked Potentials ◽

Motor Function ◽

Upper Limb ◽

Prognostic Value ◽

Motor Evoked Potentials ◽

Function Recovery

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A comparison between threshold criterion and amplitude criterion in transcranial motor evoked potentials during surgery for supratentorial lesions

Journal of Neurosurgery ◽

10.3171/2018.4.jns172468 ◽

2019 ◽

Vol 131 (3) ◽

pp. 740-749 ◽

Cited By ~ 1

Author(s):

Tammam Abboud ◽

Cindy Schwarz ◽

Manfred Westphal ◽

Tobias Martens

Keyword(s):

Evoked Potentials ◽

Sensitivity And Specificity ◽

Motor Function ◽

Stimulus Intensity ◽

Motor Evoked Potentials ◽

Threshold Level ◽

Percentage Increase ◽

Threshold Criterion ◽

Amplitude Criterion ◽

Significant Change

OBJECTIVEThe aim of this study was to compare sensitivity and specificity between the novel threshold and amplitude criteria for motor evoked potentials (MEPs) monitoring after transcranial electrical stimulation (TES) during surgery for supratentorial lesions in the same patient cohort.METHODSOne hundred twenty-six patients were included. All procedures were performed under general anesthesia. Craniotomies did not expose motor cortex, so that direct mapping was less suitable. After TES, MEPs were recorded bilaterally from abductor pollicis brevis (APB), from orbicularis oris (OO), and/or from tibialis anterior (TA). The percentage increase in the threshold level was assessed and considered significant if it exceeded by more than 20% on the affected side the percentage increase on the unaffected side. Amplitude on the affected side was measured with a stimulus intensity of 150% of the threshold level set for each muscle.RESULTSEighteen of 126 patients showed a significant change in the threshold level as well as an amplitude reduction of more than 50% in MEPs recorded from APB, and 15 of the patients had postoperative deterioration of motor function of the arm (temporary in 8 cases and permanent in 7 [true-positive and false-negative results]). Recording from TA was performed in 66 patients; 4 developed postoperative deterioration of motor function of the leg (temporary in 3 cases and permanent in 1), and showed a significant change in the threshold level, and an amplitude reduction of more than 50% occurred in 1 patient. An amplitude reduction of more than 50% occurred in another 10 patients, without a significant change in the threshold level or postoperative deterioration. Recording from OO was performed in 61 patients; 3 developed postoperative deterioration of motor function of facial muscles (temporary in 2 cases and permanent in 1) and had a significant change in the threshold level, and 2 of the patients had an amplitude reduction of more than 50%. Another 6 patients had an amplitude reduction of more than 50% but no significant change in the threshold level or postoperative deterioration.Sensitivity of the threshold criterion was 100% when MEPs were recorded from APB, OO, or TA, and its specificity was 97%, 100%, and 100%, respectively. Sensitivity of the amplitude criterion was 100%, 67%, and 25%, with a specificity of 97%, 90%, and 84%, respectively.CONCLUSIONSThe threshold criterion was comparable to the amplitude criterion with a stimulus intensity set at 150% of the threshold level regarding sensitivity and specificity when recording MEPs from APB, and superior to it when recording from TA or OO.

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