Intraoperative spinal cord monitoring: Lesional level diagnosis.

BACKGROUND: In spinal deformity surgery, iatrogenic spinal cord injury is the most feared complication. Intraoperative monitoring (IOM) of the spinal cord assesses its functional integrity and allows significant reduction of the rate of spinal cord injury. HYPOTHESIS: In case of severe IOM alert, lesional level diagnosis constitutes supplementary and useful information. MATERIAL AND METHODS: This study was retrospective and monocentric. In our institution, 1062 pediatric spinal deformity surgeries have been monitored since 2004. We review the records of the six patients who presented a severe and prolonged IOM alert with lesional level determination. Somatosensory evoked potentials (SSEP), neurogenic mixed evoked potentials (NMEP) and D-waves were performed. In cases of IOM alert, sequentially moving an epidural electrode along the spinal cord allows lesional level determination, using this electrode either for stimulation or recording. RESULTS: Six patients, aged 12 to 17 years, characterized by severe IOM alerts during spinal deformity surgery are reported. Postoperative neurological examination was normal for five out of six cases. For patient 2, lesional level diagnosis allowed to determine a bi-laminar claw between T2 and T3 as the etiology of IOM alert. This IOM alert was delayed in time, being detectable only 30minutes after the placement of this claw. Postoperative neurological examination was normal. For patient 6, a Stagnara wake-up test demonstrated paraplegia. Lesional level was established. Following corrective surgical maneuvers, postoperative neurologic deficit was limited to a pyramidal syndrome in one lower limb. Postoperative MRI demonstrated a spinal cord lesion at the determined lesional level. CONCLUSION: During an IOM alert, lesional level determination allows localization of spinal cord dysfunction. This data, obtainable whatever the IOM device, constitutes supplementary information in order to rapidly identify the etiology of IOM alert and thus to react in the most appropriate way. LEVEL OF EVIDENCE: IV, retrospective study.