Intraoperative neuromonitoring alerts during surgery for congenital spinal deformity: prevalence, risk factors, and outcomes in a prospective study of 100 patients

BACKGROUND: Surgical goals for congenital spinal deformity (CSD) include correction of deformity and prevention of progression without affecting neurological function. CSD has a higher incidence of intraoperative neuromonitoring (IONM) alerts than other scoliosis types and a potential for risk of postoperative neurological deficit. This study investigates incidence, risk factors, and outcomes associated with IONM alerts in surgically treated CSD. METHODS: A prospectively collected pediatric database was queried for surgically managed patients with CSD. Demographic, surgical, and IONM details were analyzed and neurological outcomes were tracked. RESULTS: One hundred patients were included. Diagnoses were scoliosis, kyphosis, and kyphoscoliosis. Mean dominant-plane curvature was 64°. Hemivertebrae were present in 51 patients. IONM alerts occurred in 19% of cases: 11 transcranial motor-evoked potential (TcMEP) alone and 8 both TcMEP and somatosensory-evoked potential (SSEP). Fifteen alerts occurred in patients undergoing 3-column osteotomy (3CO) and 4 posterior spinal fusion (PSF) alone. Significant risk factors for IONM alerts included curve magnitude, sagittal-deformity angular ratio (DAR), total-DAR, % blood loss (%BL), and number of levels fused. The 40% alert likelihood values were 98° (curve magnitude), 17 (S-DAR), 27.1 (T-DAR), and 52% (%BL). 3CO was not statistically correlated with a higher IONM alert rate (p = 0.145); however, higher alerts were seen in patients with osteotomy (23% vs 11%). Twenty-six alerts occurred in 19 patients; 5 had more than one alert. Most occurred during hemivertebrae excision/vertebral column resection and rod/correction maneuvers. Intraoperative mitigation measures included increasing mean arterial pressure and reducing correction. Signals returned to baseline in 58% of alerts. Four of 19 cases had a postoperative neurological deficit-all with combined TcMEP and SSEP loss-but all recovered by 4-6 weeks. CONCLUSION: This is the first, large, contemporary, multicenter prospective study to highlight a 19% incidence of IONM alerts and favorable outcomes of initial neurologic deficit in CSD. Large curve magnitude, sagittal-DAR, total-DAR, more levels fused, and %BL have significant risk associations, and 3CO cases were attributed the highest risk. Measures adopted by spine surgeons intraoperatively are described. Though most alerts can revert to baseline and do not culminate in clinical deficit, the combined loss of TcMEP and SSEP should be considered especially threatening. LEVEL OF EVIDENCE: Level III.