Continence (urine storage in the bladder) and micturition (urine elimination from the bladder) are two basic functions of the lower urinary tract. Continence requires contraction of the urethral sphincter and relaxation of the urinary bladder, while micturition occurs with a bladder contraction and a simultaneous relaxation of the urethral sphincter. The coordination between the bladder and the sphincter are under the control of brain and spinal cord. However, after spinal cord injury (SCI), these coordinated actions are lost. The bladder contracts frequently during urine storage, termed detrusor hyperreflexia (DH), which results in frequent incontinence (urine leakage). Meanwhile, during micturition the urethral sphincter contracts simultaneously with the bladder, termed detrusor sphincter dyssynergia (DSD), which prevents the bladder from empting completely. Therefore, persons with SCI leak urine frequently (i.e., frequent incontinence), but they also have difficulty in emptying their bladder during voiding (i.e., large residual volume of urine). Currently, there is no medication that can treat both DH and DSD to normalize the bladder functions after SCI. Daily urethral catheterization is the most common treatment after SCI, which can result in frequent infections of the lower urinary tract. The daily life of SCI people is burdened tremendously by these urinary problems.

In the 1970s, Brindley and his team developed an implantable sacral anterior root stimulator to restore bladder functions after SCI. This stimulator is now commercially available (Finetech Medical Limited, UK) and has been implanted in over 2000 persons around the world. However, it requires sacral posterior root rhizotomy (i.e., cutting the sensory spinal roots) that is destructive and irreversible. Sacral posterior root rhizotomy also results in the loss of reflex sexual and defecation functions that are very important residual reflexes for SCI people.

The long-term goal of our project is to develop a novel neuroprosthetic device to restore the functions of the urinary bladder for SCI people without further damaging the nervous system. Advanced technologies in electrical and computer engineering will be applied to design the novel neuroprosthetic device. Based on our previous studies, we propose in this project to use pudendal nerve stimulation and blockade to restore both continence and micturition after SCI. Our strategy does not require sacral posterior root rhizotomy, preserves the spinal reflex functions of the bowel and sexual organs, and more importantly provides the opportunity for SCI people to benefit from any advance in neural regeneration and repair techniques in the future.

The SCI population in United States is almost 250,000, and the annual cost for SCI is about $8 billion. SCI has tremendous psychological effects and huge impact on the quality of life. Of the 250,000 Americans with SCI, about 42,000 are veterans eligible for medical care from the Department of Veterans Affairs (VA). The lower urinary tract dysfunctions after SCI significantly degrade the quality of life for those injured veterans, and contribute a significant amount of cost to the VA's budget each year. Our novel neuroprosthetic device will greatly improve the quality of life for thousands of people suffering from SCI. It will also significantly reduce the burden for SCI people's family members who are currently the primary caregivers in the management of the lower urinary tract problems. The success of our project will create a novel implantable nerve stimulator to restore both continence and micturition functions for SCI people. It will fundamentally change the current medical treatments for the lower urinary tract dysfunctions after SCI. Daily urethral catheterization will not be the norm for SCI. Frequent infection of the lower urinary tract will be eliminated. The quality of life will be improved greatly for both SCI people and their families.