The brain sends that decision to the bladder, causing the bladder muscles to relax and tightening the bladder neck muscles and the sphincter. When the person is ready to urinate, the brain again sends a signal. The bladder muscles tighten and the sphincter relaxes, letting urine flow out. The InterStim system sends these messages for the patient, ensuring the brain and the nerve communicate correctly. It uses mild electrical pulses to stimulate the sacral nerve, located just above the tailbone.
Patients usually stay in the hospital only one night for observation.
Though side effects are rare, they can include pain or skin irritation at the implant site, a change in the menstrual cycle, or an adverse change in bowel function or infection. Also, the device can move inside the body. There have been no reports of serious or permanent injury associated with the InterStim. The InterStim is adjusted electronically later in life from outside the body with radio signals. The system already has helped dozens of North Carolinians such as Shelley Higgins of Leicester, who has fought infection her whole life because she was born with an underdeveloped bladder.