Individuals with neurologic disease or injury such as spinal cord injury often develop dyssynergic lower urinary tract reflexes, which can prevent bladder-voiding and compromise their health. Permanent and destructive neurotomies can allow bladder-voiding, but eliminate residual sacral sensation and disrupt reflexes governing defecation and sexual function, severely affecting quality of life. High frequency electrical (HF) stimulation can immediately and reversibly block nerve impulse conduction, effectively providing a reversible neurotomy.
This dissertation demonstrated effective bladder voiding in an acute feline model using HF stimulation. Complete bladder voiding was achieved using sacral root stimulation to activate the bladder and either PN or sacral root HF block to prevent activation of the external urethral sphincter (EUS). Effective bilateral HF PN EUS block was achieved, allowing complete bladder-voiding equivalent to voiding following pudendal neurotomy and reducing maximum bladder pressure during voiding. PN HF block for voiding extended previous research demonstrating unilateral HF PN EUS block. Sacral HF EUS block allowed bladder voiding comparable to voiding in the absence of EUS activation. Complete bladder voiding could be achieved through successive HF block trials or by extending the HF block trial duration. Development of bladder-voiding neuroprostheses utilizing sacral HF block may require only modification of existing technology. Both sacral and PN HF block bladder-voiding neuroprostheses significantly improve upon existing approaches by preserving sacral reflexes and sensation. Thus HF based bladder-voiding neuroprostheses expand the population of patients willing to consider bladder-voiding neuroprostheses, potentially improving patient quality of life and decreasing the cost of patient care.
HF block of small (1 -3 µm) myelinated parasympathetic bladder efferents at the sacral root level was also demonstrated. Small fiber block characteristics were dependent on stimulation frequency and amplitude and HF block was localized to the region near the blocking electrode. Complete, rapid nerve block and the minimization of HF evoked bladder responses could be achieved with the appropriate choice of stimulation parameters. The demonstration of small fiber HF block supports research into HF block neuroprostheses for chronic pain or autonomic disorders. Such neuroprostheses could benefit an extremely large patient population currently lacking many treatment options.