SIMULTANEOUS SOMATOSENSORY-EVOKED POTENTIAL AND ELECTROMYOGRAPHIC RECORDINGS DURING LUMBOSACRAL DECOMPRESSION AND INSTRUMENTATION

OBJECTIVE: Both motor and sensory neurological deficits have been repo rted after decompression and instrumentation of the lumbosacral spine. In this report, we describe a simple and effective method by which se nsory and motor functions can be monitored simultaneously, using somat osensory evoked potentials (SSEP), spontaneous electromyographic (EMG) activity, and compound muscle action potential monitoring. The concom itant use of these monitoring techniques allows ongoing functional eva luation of the cauda equina and spinal cord during patient positioning , surgery, wound closure, and anesthetic emergence. METHODS: SSEPs wer e recorded continuously in response to peroneal or tibial nerve stimul ation. EMG activity (both spontaneous and evoked) was recorded bilater ally from appropriate lower extremity muscle groups. All recordings (S SEP and EMG activity recordings) were obtained, stored, and reviewed s imultaneously.RESULTS: SSEPs and EMG activity were simultaneously reco rded for 44 patients. All patients in the study underwent surgical pro cedures to decompress and stabilize the lumbosacral spine, using pedic le screw instrumentation. In two cases, changes in SSEPs and spontaneo us EMG activity were noted and were correlated with postoperative pati ent complaints. CONCLUSION: This report describes the concomitant use of powerful and simple tools that provide immediate, ''early-warning'' feedback to the surgical team concerning the sensory and motor functi oning of the spinal cord and cauda equina. In addition, compound muscl e action potential recording provides a tool for the identification of both levels and structures in the lumbosacral spine.