Coordinated Microstimulation of Sacral Afferent Pathways to Control Continence and Micturition Reflexes

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Abstract The loss of normal bladder control that occurs after a spinal cord injury can lead to severe health consequences. In fact, the most common reason for hospitalization in people with spinal cord injuries is urinary tract complications that arise from deficiencies in the current clinical methods to manage bladder function. In addition, social issues surrounding regular bladder care can lead to a decrease in quality of life and surveys indicate that people with spinal cord injury desire improvements in bladder care above many other functions. Several promising approaches to improve bladder function using neurotechnologies have been proposed, however all but a few techniques have failed to reach clinical use. A fundamental limitation with previous approaches is that they have not been able to selectively or simultaneously stimulate the distributed reflex pathways known to contribute to normal function. For example, stimulation of different sensory pathways in the pudendal nerve can elicit both continence and micturition reflexes, however, these reflexes are modulated by sensory activity in the pelvic nerve. Accessing all these pathways in the peripheral nervous systems is extremely challenging. The goal of this proposal is to achieve selective activation of afferent pathways from the bladder, urethra and genitalia by implanting multielectrode arrays into the sacral dorsal root ganglia (DRG). At this interface location, we believe that sensory afferents from both the pudendal and pelvic nerves can be stimulated selectively without activating motor pathways. Using this approach, we plan to independently modulate activity in multiple reflex pathways to the spinal cord and will assess the effect on control of continence and micturition. Specifically, these experiments propose to 1) determine the patterns of afferent recruitment in response to sacral DRG microstimulation, 2) test the effects of single-channel and coordinated multichannel microstimulation of sacral DRG afferents on recruitment of storage and voiding reflexes, and 3) determine the impact of supraspinal reflex pathways on coordinated multichannel microstimulation. Success in these aims will demonstrate that the sacral DRG can be used to enable access to the distributed peripheral pathways of the lower urinary tract. This access could be useful for both fundamental investigations into the neural control of the bladder as well as for development of neuroprosthetic technologies. Ultimately, our long-term goal is to develop a device that leverages knowledge of the spinal control of continence and micturition reflexes to restore functionally normal control of the bladder to people living with injured spinal cords.