USE OF CONTINUOUS INTRAOPERATIVE ELECTORMYOGRAPHIC POTENTIAL NERVE ROOT MONITORING DURING DECOMPRESSION OF PATIENTS WITH SYMPTOMATIC LUMBAR RADICULOPATHY

Abstract

Purpose: Inadequate disc fragment excision, suboptimal bony decompression of the lateral recess, and persistent foraminal and far lateral compressive lesions are the most common cited causes for persistent radiculopathy after lumbar decompressive surgery. This study examines the utility of continous intraoperative monitoring of electromyographic (EMG) nerve root potentials during decompression of lumbar radiculopathy using a proprietary neurophysiological EMG monitoring system (Neurovision; Nuvasive; San Diego, CA).

Methods: A prospective, non-blinded, non-randomized study was undertaken in 43 patients with symptomatic lumbar radiculopathy and weakness undergoing decompressive surgery. All had previously failed conservative therapy. Preoperative and postoperative data for neurological strength examination, EMG amplitudes, VAS scores for radiculopathy were recorded. Continuous EMG nerve root potentials were monitored and recorded during surgery.

Results: At the time of surgery, 39 of 43 patients demonstrated measurable asymmetric EMG amplitudes. Of these 39, 30 patients had clinical strength improvements. Intraoperative EMG improvements were seen in 21 of these 30 patients with an overall sensitivity of 70%. Of 9 patients who did not improve in strength, 8 demonstrated no improvement or worsening on EMG for a specificity of 89%. Overall, EMG nerve root monitoring had a positive predictive value of 95.5% and a negative predictive value of 47.1% with regards to strength improvement. 3 cases had worsened transient weakness that resolved within 3 months. In detecting such injury, EMG was 100% sensitive, 97% specific with a positive predictive value of 75% and a negative predictive value of 98%.

Conclusions: Use of intraoperative EMG nerve root surveillance may provide a useful adjunct in determining the adequacy of decompression during surgery of compressive lumbar radiculopathy and may help to predict the degree of motor improvement. Although a rare complication, EMG is particularly sensitive at detecting iatrogenic injury to the nerve root during surgery.