The effect of high frequency sacral nerve stimulation on lower urinary tract function in awake, healthy animals

Many individuals with neurological disorders rely on using catheters to empty their bladder. However, catheters are associated with urethral trauma and urinary tract infections. Peripheral nerve stimulation at frequencies of 500 - 10,000 Hz is associated with reduction of muscle contraction without causing fatigue. We hypothesized that high frequency sacral nerve stimulation would be associated with reduced pelvic muscle activity without reduced bladder pressures. We implanted five healthy cats with pulse generators connected to nerve cuff electrodes on sacral nerves S1 and S2. We applied stimulation at frequencies of 20 Hz, 500 Hz, or 10 kHz. We measured bladder pressure using our custom-designed wireless, catheter-free bladder sensor, and measured pelvic floor electromyogram (EMG) as a proxy for urethral sphincter activity. Stimulation at 10 kHz was associated with a lack of increase in peak-to-peak pelvic floor EMG amplitude compared to stimulation at 20 and 500 Hz, which suggested blockade of the nerves that control the pelvic floor muscles. All three stimulation frequencies yielded bladder contractions. High frequency sacral nerve stimulation may reduce pelvic floor activity without decreasing bladder pressure. This approach may enable catheter-free bladder emptying for individuals with neurologically driven urethral sphincter overactivity.