Intraoperative neurophysiological monitoring reduces postoperative constipation in unilateral biportal endoscopic lumbar spine surgery.

INTRODUCTION: Postoperative constipation is a frequent complication following lumbar surgery under general anesthesia, potentially associated with intraoperative nerve root irritation. However, the incidence of postoperative constipation following unilateral biportal endoscopic (UBE) lumbar surgery and the potential preventive role of intraoperative neurophysiological monitoring (IONM) remain underexplored. AIM: We aimed to evaluate whether the application of IONM, anal sphincter free-running electromyography (frEMG), and the bulbocavernosus reflex (BCR) reduced the incidence of postoperative constipation in patients undergoing UBE lumbar surgery. MATERIALS AND METHODS: This retrospective cohort study included 153 patients who underwent UBE lumbar decompression between January and December 2024. The patients were divided into the IONM group (n = 50) and the non-IONM group (n = 103). Intraoperative frEMG activity and the BCR were recorded. The incidences of postoperative constipation, Visual Analog Scale scores, and perioperative outcomes were compared between the cohorts. RESULTS: Intraoperative frEMG activity and BCR amplitude reductions were observed in response to surgical manipulation. However, all BCR amplitudes returned to baseline prior to surgical closure. The incidence of postoperative constipation was 48% in the IONM group and 65.1% in the non-IONM group (P = 0.04). The rate of delayed bowel movements (within 2 days postoperatively) was 64% in the IONM group, as compared with 80.6% in the non-IONM cohort (P = 0.03). CONCLUSIONS: The use of IONM provides real-time neurophysiological feedback during UBE lumbar surgery. It facilitates minimization of aggressive nerve root manipulation, which may be associated with a reduced incidence of postoperative constipation.