Myogenic motor-evoked potential monitoring using partial neuromuscular blockade in surgery of the spine.
METHODS
The authors analyzed motor-evoked potentials using transcranial electrical cortical stimulation during spinal surgery in 40 patients under conditions of partial neuromuscular blockade.


OBJECTIVE
The results were used to investigate the utility of motor-evoked potential monitoring to prevent neurologic injury in spinal surgery.


BACKGROUND
Noninvasive transcranial electrical motor-evoked potentials are reportedly effective in predicting postoperative spinal cord deficits caused by intraoperative occurrences. However, the sensitivity and specificity of these predictions have not been assessed under conditions of partial neuromuscular blockade during a wide variety of surgical procedures.


METHODS
Compound muscle action potentials were recorded at the tibialis anterior muscle while general anesthesia was maintained with nitrous oxide, etomidate, and sufentanil. Surgery was performed at all spinal levels for a variety of diagnoses.


RESULTS
Reference motor-evoked potential amplitudes, measured after induction of partial neuromuscular blockade, ranged from 25 to 7562 microV (median, 600 microV). Variation in intraoperative motor-evoked potential amplitude ranged from signal loss to a 3440% increase. A decrease to less than 20% of the individual reference value for motor-evoked potential amplitude occurred at least once in nine patients (22.5%) but as not associated with postoperative motor deficits. Two patients who had loss of motor-evoked potential signal without recovery did have postoperative motor deficits. Motor-evoked potentials predicted postoperative motor improvement in six patients. An improvement threshold of 160% of the reference amplitude predicted postoperative motor improvement with 100% sensitivity and 81% specificity.


CONCLUSIONS
The authors support the utility of recording transcranial electrical motor-evoked potentials in spinal surgery under partial neuromuscular blockade. Recovery of lost motor-evoked potentials was not associated with postoperative motor deficits, whereas non-recovery of lost motor-evoked potentials was.
Lang
E W
EW
Division of Neurological Surgery, University of California, San Diego, USA.
Beutler
A S
AS
Chesnut
R M
RM
Patel
P M
PM
Kennelly
N A
NA
Kalkman
C J
CJ
Drummond
J C
JC
Garfin
S R
SR
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004558:Electric Stimulation; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D007432:Intraoperative Period; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D009044:Motor Cortex / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology; D019148:Neuromuscular Blockade; D011183:Postoperative Complications; D012680:Sensitivity and Specificity; D013116:Spinal Cord / Q000503:physiopathology; D013131:Spine / Q000601:surgery*; D016896:Treatment Outcome