Intraoperative neuromonitoring and mapping during spinal cord untethering surgery; a single-centre paediatric neurosurgery unit experience.

Purpose: A review of 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 and 2022 was carried out. Cohort demographics, IONM and 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: 2-9, 61% female) underwent surgery. The most common diagnosis was thickened filum (n = 59, 48%). Urological dysfunction was the most common presenting complaint (62%). Electromyography (EMG), motor evoked potentials (MEP), somatosensory evoked potentials (SSEP), and bulbocavernosus reflexes (BCR) were successfully recorded in 100%, 99%, 90%, and 73% patients. Unsuccessful BCR monitoring only occurred in females (p < 0.001). The Triggered-EMG protocol identified nerve rootlets adhered to the filum or tethering structure in 16% of the cohort. Alert criteria breaches (> 30-50% reduction in SSEP, > 80% reduction in MEP amplitude, absent BCR) occurred in 13 patients (11%). These alert criteria breaches were reversed in 11 (85%) with no permanent neurological deficits. In 2 (15%), alerts were irreversible, and one developed a permanent neurological deficit. Signs and symptoms of tethered cord had either stabilised (≥ 64%), improved (≥ 20%), or worsened (≤ 4%) at 3-month postoperative review.

Conclusion: IONM and IONMa are useful and effective tools in monitoring and identifying neural tissue, which can guide safe cord untethering and lipoma resection. Our results validate IONM and IONMa in surgery for cord untethering.