[Value of the study of somatosensory evoked potentials during surgical correction of scoliosis associated with syringomyelia. Apropos of 4 cases].

PURPOSE OF THE STUDY

The presence of a syringomyelia cavity increases the rate of neurological complications on the course of surgical treatment of scoliosis. We have evaluated the results of monitoring of somatosensory evoked potentials (SEP) in these situations.

MATERIAL AND METHODS

Four patients presenting a scoliosis associated with syringomyelia have been operated through a posterior-approach with CD instrumentation. SEP monitoring was performed pre and intraoperatively. We studied the latency and the amplitude of P40.

RESULTS

Preoperative SEP showed in all cases posterior spinal cord involvement (even without clinical manifestations). During monitoring, we noted in one case no variation. In one case a flattening of the response with normalisation within 5 minutes. In two cases a persistent flattening with normalisation within 10 and 15 minutes following modification of the instrumentation. In all cases, postoperative neurological status was identical to preoperative one.

DISCUSSION

Preoperative SEP can make the diagnosis of posterior 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 anesthetic protocol and the same technique used when operating idiopathic scoliosis. The results seem reliable. When alteration occur as for idiopathic scoliosis alteration of the amplitude appears earlier than alteration of the P40 latency. Restoration of normal responses appears later than in idiopathic scoliosis.

CONCLUSION

SEP monitoring should diminish the risk for neurological complications in the course of surgical treatment of scoliosis associated with syringomyelia.