Responding to neuromonitoring changes in 3-column posterior spinal osteotomies for rigid pediatric spinal deformities

Abstract

Study design: Retrospective review of prospectively collected data on the neuromonitoring changes recorded during a consecutive series of cord level 3-column posterior spinal osteotomies for the correction of rigid pediatric spinal deformities in children between 2005 and 2012.

Objective: To review the neuromonitoring changes observed during the performance of these procedures, to highlight the high-risk steps, and to describe actions taken to avert major neurological injury.

Summary of background data: Significant motor evoked potentials (MEP) changes are common during the performance of spinal osteotomies in children. The real-time intraoperative information provided by MEPs can provide the necessary information to direct key surgical decisions.

Methods: The neuromonitoring changes occurring during the performance of 37 3-column, cord level, posterior spinal osteotomies in 28 patients were recorded. The procedures were divided, for comparative purposes, into 2 groups based on the presence or absence of alerts. A decrease in somatosensory evoked potentials and transcranial MEPs greater than 50% of baseline was considered an alert. Alerts were classified chronologically as type I: prior to decompression, type II: occurring during decompression and bone resection, type III: occurring after osteotomy closure.

Results: Somatosensory evoked potential alerts occurred in 3 patients, all of whom had significant MEP alerts. There were 2 type I, 15 type II, and 6 type III MEP alerts. Increasing blood pressure improved MEPs in all with the exception of 8 type II and 4 type III. The unresponsive 8 type II alerts were treated with osteotomy closure with the expectation that spinal shortening would decompress the spinal cord and improve spinal cord perfusion. The unresponsive 4 type III alerts all responded to reopening, manipulation, and subsequent reclosure of the osteotomy either with a cage or less correction. There were 5 immediate postoperative motor deficits. No patient had a permanent deficit.

Conclusion: Changes unresponsive to increasing blood pressure occurring during decompression and bone resection (type II) responded well to osteotomy closure. Unresponsive changes during osteotomy closure (type III) were treated successfully with opening the osteotomy, cage adjustment, and less correction.