Genital nerve stimulation is tolerable and effective for bladder inhibition in sensate individuals with incomplete SCI

Background: Neurogenic detrusor overactivity after spinal cord injury (SCI) causes urinary incontinence and reduces bladder capacity. Surface electrical genital nerve stimulation (GNS) acutely inhibits reflex bladder contractions. The stimulation amplitude selected for GNS is typically twice the amplitude that is required to evoke the pudendal-anal reflex. There is concern about the ability of persons with sensation to comfortably tolerate effective levels of GNS. The objective of this work is to determine if persons with incomplete SCI are able to tolerate acute GNS for bladder inhibition.

Methods: Twenty-four subjects with neurogenic detrusor overactivity, SCI, and pelvic sensation were enrolled in this case series. The setting was the Spinal Cord Injury Service of a Veterans Affairs Medical Center. Primary outcome measures were sensation threshold and tolerable stimulation amplitude; secondary outcome measures were bladder capacity and bladder contraction inhibition.

Results: GNS was tolerable up to 30±16 mA (range 8 mA to ≥60 mA) at amplitudes greater than twice the pudendal-anal (PA) reflex threshold, which was 8±5 mA (range 4 mA to 20 mA). Twelve subjects tolerated GNS at greater than twice the PA, six tolerated 1-1.5 times the PA, and five had no identifiable PA. GNS at tolerable amplitudes inhibited reflexive bladder contractions or increased bladder capacity 135±109 mL (n=23). GNS did not cause autonomic dysreflexia or intolerable spasticity.

Conclusions: GNS is tolerable at amplitudes that effectively inhibit neurogenic detrusor overactivity in individuals with pelvic sensation. GNS therefore is a tool with potential clinical applications for persons with preserved sensation.