Normal functions of the lower urinary tract are storage and timely elimination of urine voiding. These functions are abnormal after spinal cord injury (SCI). Detrusor and urethral sphincter contract simultaneously during voiding (detrusor sphincter dyssynergia, DSD) and the detrusor also contracts frequently during storage (detrusor hyperreflexia, DH). DSD prevents complete elimination of urine, generates high bladder pressure and requires daily urethral catheterization. High bladder pressure causes vesicoureteral reflux and renal failure in the long-term. Residual urine in the bladder and urethral catheterization, cause cystitis and infection. In addition, DH causes a low bladder storage capacity and transient high intravesical pressures resulting in incontinence, risk for kidney damage and bladder hypertrophy. The problems of the lower urinary tract result in large medical cost and tremendous social and psychological impacts on the patients and their families. The goal of this project is to find new methods to treat both DSD and DH. Although electrical stimulation of sacral anterior roots has been successful to restore bladder control after SCI, it requires transection of sacral posterior roots (dorsal rhizotomy) to prevent DSD and DH. Dorsal rhizotomy is destructive and irreversible, and results in the loss of reflex sexual function and reflex defecation. Our new approach will utilize the remaining and newly emerged spinal reflexes after SCI to restore the lost functions, rather than further damaging the neural pathways by dorsal rhizotomy. During urine storage, we will electrically stimulate pudendal nerve afferent pathways to abolish the hyperreflexic bladder contractions and treat DH. When voiding is attempted, we will suppress pudendal nerve conduction with axonal blocking stimulation to relax the external urethral sphincter and thereby treat DSD. With this approach, a large bladder capacity and low pressure voiding with a minimal residual volume of urine will be expected. Our approach preserves the spinal reflex functions for bowel and sexual organ, and more importantly provides SCI patients the opportunity to benefit from advances in neural regeneration and repair techniques in the future.
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