MP8-16 CHRONIC BILATERAL PUDENDAL NERVE ELECTRICAL STIMULATION IMPROVES RECOVERY FROM SIMULATED CHILDBIRTH INJURY IN A STRESS URINARY INCONTINENCE MODEL

Abstract

INTRODUCTION AND OBJECTIVES: The mechanism of stress urinary incontinence (SUI) development likely involves incomplete regeneration of the pudendal nerve and repair of the external urethral sphincter (EUS). Electrical stimulation (e-stim) can increase brain-derived neurotrophic factor expression, activate Schwann cells, and promote neuroregeneration after nerve injury. The aim of this study was to determine if bilateral pudendal nerve e-stim would facilitate recovery from SUI in a simulated childbirth injury model. METHODS: Forty virgin Sprague-Dawley female rats (250e300g) received either sham injury or pudendal nerve crush (PNC) þ vaginal distension (VD) to establish a SUI model. Immediately after injury, electrodes were implanted at the pudendal nerve bilaterally. Each animal underwent sham e-stim, twice per week e-stim, or daily estim for 2 wk with subthreshold stimulation parameters (20Hz frequency, 0.1ms pulse duration, 0.3mA current). Two weeks after injury and treatment, each animal underwent leak point pressure (LPP) testing with EUS electromyography (EMG), and pudendal nerve sensory branch potential (PNSBP) recordings and was then euthanized for histology. RESULTS: Two wk after injury, LPP was significantly increased in both 2/wk e-stim and daily e-stim compared to sham e-stim. Daily estim significantly increased LPP compared to 2/wk e-stim. However, all stimulated groups had significantly decreased LPP compared to either sham injury with no electrode implant or sham injury with sham e-stim. EUS EMG and PNSBP were significantly decreased after injury with sham e-stim compared to either sham injury with no implant or sham injury with sham e-stim, but not with 2/wk e-stim and daily e-stim, indicating improved recovery after e-stim. Histology revealed that 2 wk after injury, density and morphology of pudendal nerve axons were significantly decreased compared to sham injury with no electrode implant, but improved after 2/wk and daily e-stim. Neuromuscular junction innervation was significantly decreased after injury, but improved after 2/wk and daily e-stim. Masson’s trichrome revealed that morphology of the EUS significantly decreased compared to sham injury, but improved with 2/wk and daily e-stim. CONCLUSIONS: This study demonstrates that chronic bilateral e-stim to the pudendal nerve is feasible and can accelerate recovery in a model of SUI. Daily e-stim provides better preservation of urethral function than twice per week e-stim.