Effect of 600-Hz Sacral Root Stimulation on Lower Urinary Tract and Bowel Function in Three Individuals With Spinal Cord Injury: A Case Series

Spinal cord injury typically leads to neurogenic bladder dysfunction, often including detrusor-sphincter dyssynergia. Sacral anterior root stimulation can empty the neurogenic bladder, but this emptying can be impeded by reflex contractions of the urethral sphincter. The sacral sensory roots are typically transected (rhizotomy) to reduce these reflex contractions, but this rhizotomy also impairs desirable reflexes (e.g., sexual function) and sacral sensation, if present. Preclinical experiments have shown that sacral nerve stimulation at 600 Hz can promote bladder emptying while reducing urethral sphincter activity. In this proof-of-concept study, we tested 600-Hz sacral nerve stimulation to limit urethral sphincter activity in individuals with spinal cord injury who were already implanted with a sacral anterior root stimulation device. Bladder pressure, urethral pressure, rectal pressure, anal pressure, and pelvic floor electromyogram were measured in response to stimulation at 20 or 600 Hz. Stimulation was feasible and well-tolerated, and frequency appeared to have an effect on lower urinary tract and bowel function. In one participant, stimulation at 600 Hz produced a significant decrease in urethral pressure compared to 20-Hz stimulation. Further work is needed to explore the potential for this approach to improve bladder emptying efficiency for individuals with spinal cord injury and detrusor-sphincter dyssynergia.