Mechanically elicited nerve root discharge: mechanical irritation and waveform

Objective - Intraoperative monitoring is very important for protecting nerv e roots during lumbar surgery for spinal degeneration. Our objective was to evaluate the correlation between the type of mechanical irritation and wav eform by mechanically elicited EMGs during the surgery. Methods - Mechanica lly elicited EMGs were recorded bilaterally on muscle groups innervated by the lumbar nerve roots in the area of surgery in 24 consecutive patients wi th lumbar spinal degenerative disease. Results - It was confirmed that surg ical irritation produced 3 types of waveforms as discharges from nerve root s; short, waning and continuous discharges. Each waveform was easily elicit ed mechanically and was sensitively related to the type and strength of mec hanical stimulation. Conclusion - It was indicated that the mechanical irri tation on the root could elicit the nerve root discharge with no post-opera tive nerve root deficit. It may be useful to monitor the mechanically elici ted EMGs during the surgery for spinal degeneration.