Neurophysiologic monitoring of spinal nerve root during lumbar intra-pedicular screw fixation / 中华创伤杂志

ABSTRACT

Objective To determine the effectiveness and clinical result of intraoperative monitoring of compound muscle action potential (CMAP) in avoiding nerve root impingement during lumbar spine intrapedical instrumentation. Methods Twenty-five cases were given intraoperative stimulus-evoked electromyographic monitoring. After anode of stimulating electrode was placed at the Kirschner wire inside the passage of pedicle screws, the integrity of the pedicle cortex was tested by stimulating each screw head and recording compound action potentials of relevant muscles. Results Stimulation at an intensity of 16.2 mA evoked a compound muscle action potential in one case and that at over 35 mA did in four cases. No neurologic deficits were found in any case intraoperatively or postoperatively. Conclusions Stimulating intensity below 10 mA needs rearranging screw site. A stimulation intensity of 10-20 mA indicates X-ray inspection and visual inspection to exclude any pedicle breaches. Stimulation thresholds above 20 mA can be regarded as safe threshold to monitor the nerve root impingement. Intraoperative electromyographic monitoring provides a real-time watch-dog for monitoring spinal nerve root injury during posterior lumbar instrumentation.