Intraoperative neuromonitoring and mapping during spinal cord untethering surgery. Preliminary findings from a single-centre paediatric neurosurgery unit.

Objective To review intraoperative neuromonitoring (IONM) and mapping (IONMa) utility during paediatric tethered cord surgery with particular attention to feasibility, measures to prevent injury, and postoperative outcome. Methods A retrospective analysis of spinal cord untethering surgery between 2015-2022. Cohort demographics, clinical and imaging characteristics of tethered cord, IONM/IONMa data and procedural details were summarised and associations between variables explored. Clinical outcome was assessed 3-months post procedure via review of medical records. Results One hundred and twenty-two patients (Median age: 3 years old: IQR: 2-7, 61% Female) underwent surgery with IONM/IONMa, most with a Morota 4 lipoma (n=35, 29%) or fatty/thickened filum (n=26, 21%). Urological dysfunction was the most common presenting complaint (n=76, 62%). EMG, MEP, SSEP, BCR were successfully recorded in 100%, 99%, 90%, and 73% of patients respectively. Unsuccessful BCR monitoring was associated with gender (p<0.001) and Morota lipoma category (p=0.039). Our Tr-EMG protocol identified rootlets adhered to the filum in 16% of filum disconnection surgeries. Alert criteria breaches (>50% SSEP amplitude reduction, >80% MEP amplitude reduction, absent BCR) were associated with Morota lipoma category (p=0.037) and occurred in 13 patients (11%). These were reversed in 11 (85%) with no permanent neurological deficit. In 2 (15%), alerts were irreversible, and one developed a permanent neurological deficit. Signs/symptoms of tethered cord had stabilised (≥64%), improved (≥20%), or worsened (≤4%) at 3-month postoperative review. Conclusion IONM/IONMa is a useful and effective tool in monitoring and identifying neural tissue, which can guide safe cord untethering and lipoma resection. Our results validate IONM/IONMa in surgery for cord untethering.