Introduction: Neurophysiological monitoring during spinal surgery reduces the associated neurological complications. Continuous EMG recording has developed an useful technique for spinal root monitoring
Patients and methods: Fifty four patients who underwent surgery for several lumbosacral spinal lesions (low and high degree spondylolisthesis, spinal stenosis, degenerated or herniated lumbar discs) were studied to evaluate the effectiveness of continuous EMG recording in monitoring spinal root function during surgery. Electrical root or screw stimulation was also performed in nine of them. To correlate surgical spinal root lesion with a precise EMG injury activity an animal study with 5 pigs was performed; lesion was produced by prolonged spinal root traction.
Results: In the porcine group EMG discharges lasting longer than one minute after cessation of root traction was noted in 74% of spinal root levels (neurotonic discharges or pseudo-rhythmic activity in 70% of the cases). Spinal root lesion was demonstrated through EMG three weeks after surgery. In the patient group pathological-significant EMG activity was not recorded in any case during monitoring. Mechanical or chemical root stimulation during surgery produced brief lasting EMG bursts of no pathological significance. Only a patient developed a mild acute L5-S1 radiculopathy after surgery (1 false negative) and post-operative deficit was not observed in the rest. Electrical stimulation of spinal roots and screws allowed to identify root level and prove the adequate placement of screws.
Conclusion: Spontaneous and evoked EMG recordings are simple techniques that provide continuous information about lumbosacral spinal roots function throughout surgery.