Sequential intraoperative protocol to improve bulbocavernosus reflex monitorability during pediatric spinal surgery

Bulbocavernosus reflex (BCR) monitoring assesses sacral S2 to S4 pathway integrity during pediatric spinal surgery; however, its intraoperative utility is limited when responses are absent or unilateral. We prospectively evaluated a sequential intraoperative protocol designed to improve the interpretation of these patterns and reduce uncertainty during sacral monitoring.

We prospectively studied 242 consecutive pediatric patients aged 0.4-12 years who underwent spinal surgery between 2023 and 2025. Bilateral external anal sphincter (EAS) recordings were obtained using subdermal-needle electrodes. Intramuscular placement was verified using tetanic stimulation. BCR responses were elicited using single-train stimulation (STS), followed by double-train stimulation (DTS). A persistent absence with failed EAS verification was classified as a pattern consistent with efferent nonacquisition, whereas a persistent absence despite preserved verification was classified as a pattern consistent with afferent nonacquisition.

Final BCR acquisition was achieved in 225 of 242 patients (93.0%; 95% CI, 89.3-95.7). STS produced bilateral responses in 61.2% of patients, whereas DTS increased bilateral acquisition to 87.2%, rescued 57.5% of initially absent responses, and converted 81.5% of unilateral responses to bilateral responses. Persistent absence was observed in 17 patients (7.0%), including nine patterns consistent with efferent nonacquisition and eight with afferent nonacquisition. Younger age was independently associated with persistent absence.

A sequential protocol that combines EAS verification with DTS improves the intraoperative interpretation of BCR findings during pediatric spinal surgery. It provides a practical framework for interpreting absent or unilateral responses and reducing uncertainty when nonacquisition persists.