High Frequency SARS for Neurogenic Bladder and Bowel Emptying

Overview

The purpose of this study is to determine if bladder emptying can be achieved using stimulation of the sacral roots at certain frequencies. Neurogenic bladder dysfunction occurs after spinal cord injury (SCI). It is a problem that often includes detrusor-sphincter-dyssynergia (DSD), which results in difficulty emptying the bladder due to reflex urethral sphincter contractions during bladder emptying. Individuals with DSD typically require a catheter to empty their bladder. Some people have received an implanted device that stimulates the spinal nerves that connect to the bladder to empty the bladder without a catheter. However, this procedure usually also includes cutting nerves to stop unwanted reflexes. For this study, the investigators are testing a new stimulation pattern to determine if it can help achieve bladder emptying without having to cut nerves. Individuals with SCI who have received an implanted sacral root stimulation device are being asked to participate in this research to test the effectiveness of electrical stimulation to relax the urethral sphincter and promote bladder emptying.

Background: Spinal cord injury (SCI) leads to neurogenic bladder dysfunctions, and often includes difficulty with emptying the bladder due to detrusor-sphincter dyssynergia (DSD). Current bladder management strategies include catheterization, pharmaceuticals, and/or surgery, but these interventions insufficiently meet individuals' needs. The neurogenic bladder can be emptied using sacral anterior root stimulation (SARS) with electrodes implanted on the sacral nerves to produce bladder contractions. However, 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. Experiments in animals have shown that sacral root stimulation at 600 Hz can inhibit urethral sphincter activity, which has the potential. This approach could be used in lieu of the rhizotomy to improve bladder emptying efficiency. Objective: The objective of this study is to test the feasibility and potential effectiveness of 600 Hz sacral root stimulation to limit urethral sphincter activity in individuals with neurogenic bladder dysfunction. The investigators hypothesize that sacral root stimulation at 600 Hz will result in lower urethral sphincter pressures compared to pressures in response to stimulation at the lower frequencies that are typically used for SARS. Study Design: In this feasibility study, the investigators will enroll 8 participants, male or female, who have SCI and who already use implanted sacral root anterior stimulation to manage their bladder. Participants will act as their own controls. Stimulus waveforms for urethral sphincter inhibition will be tested in the clinical laboratory in a single session. The investigators will not need to conduct new surgeries or implant procedures. The primary outcome measure is urethral sphincter pressure, and additional outcome measures include bladder pressure, rectal pressure, and bladder volume as measured in clinically standard urodynamics examination. Clinical Impact: This approach could help restore bladder function by reducing urethral sphincter activity that impedes bladder emptying for individuals with SCI. The investigators could improve approaches for promoting bladder emptying by eliminating the need for sacral posterior rhizotomy.