Design of an implant for preventing incontinence after spinal cord injury.

An implanted device is being designed and tested which has the main function of suppressing hyperreflexic bladder contractions by stimulating the pudendal afferent pathway. The concept is that the contractions will be detected by recording natural nerve signals. This is challenging because the changes in neural signal are very small (sub-microvolt), and the device must run 24 h per day, which means that for convenience it must be battery-powered. The energy budget is therefore tight. Furthermore, because the patient must be able to intervene to occasionally empty the bladder, a radio link is needed to the device. Within the EU project Healthy Aims, most aspects of the design have been made and tested. This includes the battery, battery charger, neural amplifier, and the package incorporating the Medical Implant Communication System (MICS) antenna, which are briefly described here. This article is a progress report.