Dual Simulated Childbirth Injuries Result in Slowed Recovery of Pudendal Nerve and Urethral Function

Abstract

Pelvic floor muscle trauma and pudendal nerve injury have been implicated in stress urinary incontinence (SUI) development after childbirth. In this study, we investigated how combinations of these injuries affect recovery. Sixty-seven female Sprague-Dawley rats underwent vaginal distension (VD), pudendal nerve crush (PNC), PNC and VD (PNC + VD), pudendal nerve transection (PNT), or served as unmanipulated controls. Four days, 3 weeks, or 6 weeks after injury, we simultaneously recorded pudendal nerve motor branch potentials (PNMBP), external urethral sphincter electromyography (EUS EMG), and transurethral bladder pressure under urethane anesthesia. The presence of a guarding reflex (increased frequency and amplitude of PNMBP or EUS EMG activity) during leak point pressure (LPP) testing was determined. Controls consistently demonstrated a guarding reflex. Four days after VD, EUS EMG activity was eliminated, but PNMBP activity reflected the guarding reflex; EUS EMG activity recovered after 3 weeks. Four days after PNC, both EUS EMG and PNMBP activity were eliminated, but demonstrated significant recovery at 3 weeks. Four days after PNC + VD both EUS EMG and nerve activity were eliminated, and little recovery was observed after 3 weeks with significant recovery of the guarding reflex 6 weeks after injury. Little recovery was observed at all time points after PNT. LPP results mirrored the reduction in EUS EMG activity. Functional recovery occurs more slowly after PNC + VD than after either PNC or VD alone. Future work will be aimed at testing methods to facilitate neuroregeneration and recovery after this clinically relevant dual injury.