Severe Cerebral Palsy and Short Stature Predict Absent Baseline IONM Signals in Pediatric Neuromuscular Scoliosis Surgery

Background: Intraoperative neurophysiological monitoring (IONM) is essential for detecting potential neurological injury during scoliosis surgery, but obtaining recordable baseline signals can be challenging in neuromuscular scoliosis (NMS) patients. Absent baseline IONM signals, characterized by unattainable initial IONM responses despite technical and anesthetic optimization, present significant challenges to intraoperative neurological assessment and surgical risk stratification. This study aims to identify predictive factors for absent baseline IONM signals in pediatric NMS patients and establish a clinically applicable risk prediction model. Methods: This retrospective study initially identified 118 nonambulatory NMS patients under 18 years old who underwent spinopelvic fusion between 2013 and 2022. All patients received standardized total intravenous anesthesia (TIVA) protocol to optimize signal acquisition. After excluding 3 patients with spinal cord injuries, 115 patients were analyzed. Multimodality IONM, including somatosensory evoked potentials (SSEPs) and transcranial electrical motor evoked potentials (TcMEPs) was attempted in all cases. Clinical data and radiographic measurements were analyzed to determine predictive factors for absent baseline IONM signal. ROC curve analysis and logistic regression were used to determine optimal thresholds and predictive factors for absent baseline IONM signals. Results: Thirty-eight (33%) had absent baseline lower extremity IONM signals. Cerebral palsy (CP) was the most significant predictive factor [odds ratio (OR): 9.615, P <0.001], with 53.1% of CP patients having absent baseline IONM signals. Within the CP cohort, Gross Motor Function Classification System (GMFCS) level V (OR: 11.501, P =0.028) and body height <128.5 cm (OR: 4.097, P =0.044) were significant risk factors. Three patients developed new-onset urinary incontinence postoperatively, though the relationship to IONM status remains undetermined. Conclusion: Severe CP and shorter stature significantly increase the risk of absent baseline IONM signals in pediatric NMS patients. These findings inform preoperative risk assessment, enhance patient-specific surgical planning, and suggest the need for alternative monitoring approaches in high-risk cases. Such early identification of monitoring challenges can improve surgical preparation, consent processes, and ultimately patient care in this vulnerable population. Level of Evidence: Level III.