Mechanically elicited nerve root discharge: mechanical irritation and waveform

Abstract

Objective– Intraoperative monitoring is very important for protecting nerve roots during lumbar surgery for spinal degeneration. Our objective was to evaluate the correlation between the type of mechanical irritation and waveform by mechanically elicited EMGs during the surgery. Methods– Mechanically elicited EMGs were recorded bilaterally on muscle groups innervated by the lumbar nerve roots in the area of surgery in 24 consecutive patients with lumbar spinal degenerative disease. Results– It was confirmed that surgical irritation produced 3 types of waveforms as discharges from nerve roots; short, waning and continuous discharges. Each waveform was easily elicited mechanically and was sensitively related to the type and strength of mechanical stimulation. Conclusion– It was indicated that the mechanical irritation on the root could elicit the nerve root discharge with no post‐operative nerve root deficit. It may be useful to monitor the mechanically elicited EMGs during the surgery for spinal degeneration.

False-negative transcranial motor evoked potentials (TcMEPs) during surgery for congenital lumbar kyphoscoliosis: a case report

“…On the other hand, sustained tonic activity in freerun EMG has been reported to be related to sustained traction and compression of nerve roots, and is more associated with neural injury. 5,7,12,15,16 However, several authors have included not only train activity, but also burst activity, in the warning criteria for freerun EMGs, which might result in high sensitivity and low specificity in free-run EMG monitoring. 12,14,17 Therefore, to establish definite warning criteria for free-run EMG monitoring, it is necessary to analyze true-positive cases in detail.…”

Intraoperative Mapping of Roots, Plexuses, and Nerves

“…Spontaneous EMG that appears during lumbar spine surgery can be of different frequency and amplitude (Obi et al, 1999). These include the following: continuous activity, 150 to 200 Hz activity, lasting for tens of seconds and short EMG activity lasting up to 100 milliseconds.…”

Utility of Electromyography for Nerve Root Monitoring During Spinal Surgery

“…Compression of nerve roots is known to produce a lasting conduction block that may be detected by tEMG if not by sEMG (Pedowitz et al, 1992). Obi et al (1999) elucidated the types of sEMG activity produced by mechanical stimulation in human lumbar spine surgery. Short (,100 ms), waning (activity of 150 to 200 Hz lasting for tens of seconds, with continuously decreasing amplitude) and continuous discharges caused by nerve root retraction (200-300 Hz, lasting for tens of seconds without decrement) were noted in 96%, 79% and 42%, respectively, of lumbar spine surgery patients.…”