Pudendal nerve stimulation recruits the urethra during awake human cystometry

This study aimed to characterize the activation of lower urinary tract (LUT) targets in response to pudendal nerve stimulation (PNS) in awake human participants.

In this single center study, recruited participants had an implanted pudendal neurostimulator for treatment of their symptoms including overactive bladder, incontinence, urinary retention, and/or pelvic pain. Participants came in for a modified urodynamic study where a multichannel manometry catheter was placed in the lower urinary tract alongside a dual sensor urodynamics catheter. The bladder was filled and after each participant expressed a strong desire to void, PNS was applied and LUT pressures were measured. Participants attempted voids with the catheters in place to characterize LUT behavior and voiding efficiency with and without stimulation.

The study consisted of 15 sessions with 2 male participants and 11 female participants, with 2 female participants completing two sessions. PNS-driven urethra pressure changes were observed in 50% (31/62) of high frequency (30-33 Hz) trials and 34% (24/71) of low frequency (2-3.1 Hz) trials. There was a significantly higher maximum tolerable stimulation amplitude for low frequency stimulation when compared to high frequency stimulation (p = 0.015). During high frequency stimulation, the maximum observed pressure change occurred significantly more often at the proximal urethra than the distal urethra (p = 0.007). In one participant there were four instances of stimulation driven bladder contractions with an average pressure change of 24.3 cmH ₂ O (standard deviation = 10.5). There was not a significant difference in voiding efficiency or maximum flow rate with and without stimulation (p = 0.76 and p = 0.45, respectively).

PNS can affect LUT pressures at tolerable stimulation amplitudes. The absence of an effect of PNS on voiding characteristics suggests a similar mechanism of action as sacral neuromodulation.