Search

Background/Purpose Few studies have investigated the feasibility of using pudendal neuromodulation to regulate bladder function in spinal cord-injured (SCI) animals. The present study aimed to determine the effects of electrical activation of the pudendal sensory branch on improving voiding functions in rats 6 weeks after a spinal cord injury and to explore the underlying neuromodulatory mechanisms. Methods Two urodynamic measurements were used to assess the effects of electrical stimulation (ES) on bladder and urethral functions: simultaneous recordings of the intravesical pressure (IVP) during continuous isotonic transvesical infusion (i.e., isotonic IVP) and external urethral sphincter (EUS) electromyography (EUS-EMG), and simultaneous recordings of transvesical pressure under isovolumetric conditions (i.e., isovolumetric IVP) and urethral perfusion pressure (UPP). Results Six weeks after the SCI, the rats showed voiding dysfunction, as indicated by abnormal cystometric measurements (e.g., increased volume threshold, increased contraction amplitude, and increased residual volume, and decreased voided volume). The voiding efficiency (VE) decreased to 13% after the SCI, but increased to 22–34% after applying pudendal afferent stimulation. In addition, pudendal stimulation significantly increased the EUS burst period and increased the difference between the UPP and the high-frequency oscillation (HFO) baselines, and changed the time offset between bladder and EUS activities. These findings suggest that pudendal afferent stimulation improved the VE by prolonging the micturition interval, decreased the urethral resistance, and recovered detrusor-sphincter dyssynergia during the voiding phase. Conclusion This study demonstrates the feasibility of using pudendal neuromodulation in chronic SCI rats. These results could aid in developing an advanced neural prosthesis to restore bladder function in clinical settings.

Block of the external urethral sphincter contractions by using high frequency electrical stimulation of the pudendal nerves is a potential method for inhibiting detrusor sphincter dyssynergia. Most researchers use high frequency electrical stimulation at frequencies between 2kHz to 20kHz, but the parameters and mechanism of this block are not well understood. This paper demonstrated the use of radio frequency electrical stimulation (500kHz) as a method to block the external urethral sphincter contractions and improved voiding efficiency by electrical stimulation of unilateral pudendal nerve efferent axons. The most efficient waveform for conduction was 500kHz (with 0.2 to 1mA) constant-current biphasic sinusoidal, voiding efficiency increased from 53 to 71-92%. These results raise the possibility that using radio frequency electrical stimulation to block external urethral sphincter contraction may provide a new approach for improving voiding in spinal cord injured patients.