Control of Bladder Function by Electrical Stimulation of Pudendal Afferents

Abstract

<p>Spinal cord injury (SCI) and other neurological diseases and disorders can cause urinary dysfunction that can cause serious health problems and reduce an individual's quality of life. Current methods for treating urinary dysfunction have major limitations or provide inadequate improvement in urinary symptoms. Pudendal nerve stimulation is a potential means of restoring control of bladder function in persons with neurological disease or spinal cord injury. Bladder contraction and relaxation can be evoked by pudendal afferent stimulation, and peripheral pudendal afferent branches may be ideal targets for a bladder control neural prosthesis. This dissertation investigates control of bladder function by selective activation of pudendal afferents.</p> <p>This study investigated the ability to improve both urinary continence and micturition by both direct and minimally-invasive electrical stimulation of selected pudendal afferents in &#945;-chloralose anesthetized male cats. Direct stimulation of the pudendal afferents in the dorsal nerve of the penis (DNP), percutaneous DNP stimulation, and intraurethral stimulation were used to investigate the bladder response to selective activation of pudendal afferents. Finite element modeling of the cat lower urinary tract was used to investigate the impact of intraurethral stimulation location and intraurethral electrode configuration on activation of pudendal afferents. Also, the impact of pharmacological and surgical block of sympathetic activity to the bladder on the bladder reflexes evoked by DNP stimulation was investigated to determine the role of the sympathetic bladder innervation on the mechanism of bladder activation by pudendal afferent stimulation.</p> <p>The DNP is an ideal target for restoring urinary function because stimulation at low frequencies (5-10 Hz) improves urinary continence, while stimulation at high frequencies (33-40 Hz) improves urinary voiding. Intraurethral stimulation is a valid method for clinical investigation of the ability to evoke bladder inhibition and activation via selective activation of the DNP or cranial sensory branch (CSN) of the pudendal nerve. In the cat, intraurethral stimulation can activate the bladder via two distinct neural pathways, a supraspinal pathway reflex activated by the CSN and a spinal reflex activated by the DNP. Finite element modeling revealed the importance of urethral location for selective pudendal afferent activation by intraurethral stimulation. Finally, the sympathetic bladder pathway does not play a significant role in the mechanism mediating bladder activation by DNP stimulation. These findings imply that selective pudendal afferent stimulation is a promising approach for restoring control of bladder function to individuals with SCI or other neurological disorders.</p>