Intraoperative Neurophysiological Monitoring in Spina Bifida and Tethered Cord Surgeries: A Systematic Review of Clinical Outcomes

Abstract

Spina bifida and tethered cord syndrome (TCS) are forms of spinal dysraphism requiring surgical intervention to prevent progressive neurological decline. Intraoperative neurophysiological monitoring (IONM) provides real-time feedback, allowing surgeons to minimize intraoperative injury during these procedures. This systematic review analyzed 19 primary studies published between 2015 and 2025 examining the role of IONM techniques, including somatosensory evoked potentials (SSEP), motor evoked potentials (MEP), electromyography (EMG), and bulbocavernosus reflex (BCR), in spina bifida and tethered cord surgeries. Methodological quality and risk of bias were formally appraised using the Methodological Index for Non-Randomized Studies (MINORS) criteria. Multimodal IONM use was associated with favorable postoperative motor outcomes. Conversely, bladder and sphincter outcomes were more variable, particularly in complex or reoperative cases. The included literature demonstrated an overall moderate risk of bias, driven primarily by retrospective designs and lack of blinded outcome assessments. Longer-term comparative data suggested that differences between monitored and unmonitored cohorts may become more apparent over time, although this pattern remains hypothesis-generating. In lower-risk surgeries such as isolated filum terminale release, patients achieved favorable outcomes regardless of monitoring status, indicating limited added value of IONM in this subgroup. These findings support the selective, risk-adapted use of IONM while highlighting a moderate baseline risk of bias in the current literature. This underscores the need for standardized protocols and high-quality prospective studies with extended follow-up.