SOMATOSENSORY-EVOKED POTENTIALS IN SURGIC AL-TREATMENT OF SCOLIOSIS ASSOCIATED WITH SYRINGOMYELIA - REPORT ON 4 CASES

Purpose of the study The presence of a syringomyelia cavity increases the rate of neurological complications on the course of surgical treat ment of scoliosis. We have evaluated the results of monitoring of soma tosensory evoked potentials (SEP) in these situations. Material and Me thods Four patients presenting a scoliosis associated with syringomyel ia have been operated through a posterior-approach with CD instrumenta tion. SEP monitoring was performed pre and intraoperatively, We studie d the latency and the amplitude of P40. Results Preoperative SEP showe d in all cases posterior spinal cord involvement (even without clinica l manifestations). During monitoring, we noted in one case no variatio n. In one case a flattening of the response with normalisation within 5 minutes. In two cases a persistent flattening with normalisation wit hin 10 and 15 minutes following modification of the instrumentation. I n all cases, postoperative neurological status was identical to preope rative one. Discussion Preoperative SEP can make the diagnosis of post erior spinal cord involvement even when clinical status is normal. The extent of the preoperative SEP abnormalities may preclude the risk of intraoperative neurological complications. Intraoperative SEP can be performed with the same anesthesic protocol and the same technique use d when operating idiopathic scoliosis. The results seem reliable. When alteration occur as for idiopathic scoliosis alteration of the amplit ude appears earlier than alteration of the P40 latency. Restauration o f normal responses appears later than in idiopathic scoliosis. Conclus ion SEP monitoring should diminish the risk for neurological complicat ions in the course of surgical treatment of scoliosis associated with syringomyelia.