Responding to Intraoperative Neuromonitoring Changes During Pediatric Coronal Spinal Deformity Surgery.

STUDY DESIGN: Retrospective case study on prospectively collected data. OBJECTIVES: The purpose of this explorative study was: 1) to determine if patterns of spinal cord injury could be detected through intra-operative neuromonitoring (IONM) changes in pediatric patients undergoing spinal deformity corrections, 2) to identify if perfusion based or direct trauma causes of IONM changes could be distinguished, 3) to observe the effects of the interventions performed in response to these events, and 4) to attempt to identify different treatment algorithms for the different causes of IONM alerts. METHODS: Prospectively collected neuromonitoring data in pre-established forms on consecutive pediatric patients undergoing coronal spinal deformity surgery at a single center was reviewed. Real-time data was collected on IONM alerts with >50% loss in signal. Patients with alerts were divided into 2 groups: unilateral changes (direct cord trauma), and bilateral MEP changes (cord perfusion deficits). RESULTS: A total of 97 pediatric patients involving 71 females and 26 males with a mean age of 14.9 (11-18) years were included in this study. There were 39 alerts in 27 patients (27.8% overall incidence). All bilateral changes responded to a combination of transfusion, increasing blood pressure, and rod removal. Unilateral changes as a result of direct trauma, mainly during laminotomies for osteotomies, improved with removal of the causative agent. Following corrective actions in response to the alerts, all cases were completed as planned. Signal returned to near baseline in 20/27 patients at closure, with no new neurological deficits in this series. CONCLUSION: A high incidence of alerts occurred in this series of cases. Dividing IONM changes into perfusion-based vs direct trauma directed treatment to the offending cause, allowing for safe corrections of the deformities. Patients did not need to recover IONM signal to baseline to have a normal neurological examination.

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

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.

Neurophysiological changes in deformity correction of adolescent idiopathic scoliosis with intraoperative skull-femoral traction.

STUDY DESIGN: Retrospective review of 36 consecutive patients undergoing coronal plane deformity correction with intraoperative skull-femoral traction between 2005 and 2008 with motor evoked potential (MEP)/somatosensory evoked potential monitoring. OBJECTIVE: To determine the prevalence and significance of neurophysiological changes with intraoperative skull-femoral traction in adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Intraoperative skeletal traction can be associated with spinal cord stretching and ischemia with resultant electrophysiological changes. The prevalence and risks of such changes and their clinical significance is unknown. METHODS: Thirty-seven procedures involving 36 patients (27 females and 9 males) with a mean age of 14.8 (12-18) years were divided into two groups on the basis of the presence (group 1, n = 18 procedures) or absence (group 2, n = 19) of significant MEP changes with surgery. They were compared with patients undergoing correction without traction (group 3). RESULTS: Significant differences among the groups were observed in mean preoperative Cobb angle (86° vs. 70° vs. 59°), mean intraoperative posttraction Cobb angle (50.0° vs. 34.6°), traction index (0.41 vs. 0.50), flexibility index (0.14 vs. 0.27 vs. 0.25), and presence of primary lumbar curves (0% vs. 32% vs. 14%). Initial onset of MEP amplitude loss (group 1) occurred at a mean of 94 (1-257) minutes from the onset of surgery, was bilateral in 13 procedures, and improved at a mean of 5.5 (1-29) minutes after decreasing or removing the traction. At closure, complete bilateral recovery to baseline was observed in 10 procedures, recovery to >50% baseline in five, and recovery to <50% baseline in three procedures. There were no neurologic deficits in this series. CONCLUSION: Intraoperative traction is associated with frequent changes in MEP monitoring. The thoracic location of the major curve, increasing Cobb angle, and rigidity of major curve are significant risk factors for changes in MEP with traction. The presence of any MEP recordings irrespective of its amplitude at closure was associated with normal neurological function. Somatosensory evoked potential monitoring did not correlate with the traction induced MEP amplitude changes.