The benefit of neurogenic mixed evoked potentials for intraoperative spinal cord monitoring during correction of severe scoliosis: a case study.

Study Design: A case report is presented.

Objective: To present a case in which surgical correction of a severe scoliotic curve caused unilateral loss of neurogenic mixed evoked potential data despite unchanged somatosensory data.

Summary Of Background Data: Surgical correction of large scoliotic curves presents a risk to the function of the spinal cord. Multimodality intraoperative neurophysiologic monitoring of the spinal cord is recommended during such procedures.

Methods: A 13-year-old girl with severe double major scoliosis underwent a staged operative procedure for correction of her spine deformity. Intraoperative neurophysiologic monitoring using somatosensory-evoked potentials and neurogenic mixed evoked potentials was performed for each stage.

Results: During the final stage (a T4-L5 posterior instrumentation and fusion) left neurogenic mixed evoked potential data were lost approximately 45 minutes after placement of the left-side, correcting rod. The surgeon was warned of the data change. Set bolts were loosened at all fixation points, and the data quickly returned to within normal limits of baseline. Somatosensory data never approached warning criteria at any point during surgery. The patient awakened with no neurologic deficit.

Conclusions: Neurophysiologic monitoring using both somatosensory-evoked potentials and neurogenic mixed evoked potentials is recommended when surgery is performed to correct spine deformity. The Stagnara wake-up test, somatosensory-evoked potentials, and neurogenic mixed evoked potentials are important components of spinal cord monitoring during surgery, and should be used together for optimal protection of neurologic function.