Intraoperative neurophysiological monitoring during spinal surgery

Spinal stenosis due to degenerative changes may damage neural structures. Neurological deficits during surgical decompression of spinal stenosis have been reported within a rate of 1-33%.The aim of this study was to evaluate the effectiveness of multimodal intraoperative neurophysiological monitoring (MIONM) in detecting and preventing impending injuries to the spinal cord or nerve roots.MIONM was performed in 14 patients with spinal stenosis.Motor evoked potentials were stimulated transcranially via corkscrew electrodes with M3?-Mz6 and M4?-Mz6 electrode montages. A train-of-five pulse with duration of 1 msec was used. Recordings were obtained from related muscles with needle electrodes.Bilateral tibial and median (or occasionally ulnar) nerves were stimulated successively and somatosensory evoked potentials were recorded via corkscrew electrodes mounted at Cz?-FPz, inion-FPz for lower and C3?-FPz, C4?-FPz for upper extremities.Monitoring was performed with respect to basal measurements recorded following the induction of anesthesia. Complete loss or more than 50% decrement in the amplitudes of the potentials was accepted as significant.Monitorization could not be achieved in one patient. Among the 13 monitorized patients, one was accepted as true positive and 12 as true negative (%92,3). Postoperative neurological deficits did not occur in any of the patients.MIONM is an important means of preventing permanent neurological deficits and ensuring conservation of function and quality of life. More practice is necessary to gain experience in this area.Key Words: Spinal stenosis, Multimodal intraoperative neurophysiological monitoring