by combining body weight-supported treadmill training with other approaches, such as robotic devices (Dobkin and Havton, 2004), drugs, and surgery.

Functional Electrical Stimulation

Functional electrical stimulation (FES) is the approach most commonly used to artificially improve muscle function. FES devices have two key components: a control unit and stimulating electrodes. The control unit translates commands from voluntary movements or sensors into signals that are sent to the stimulating electrodes, which are taped onto the skin or surgically positioned near the specific nerves that innervate muscle groups (Bhadra et al., 2001). The stimulating electrodes provide mild shocks to muscle groups, causing them to contract (Barbeau et al., 2002). These contractions help maintain muscle mass and can initiate muscle movements, such as controlling movements of the hands or legs (Peckham et al., 2002). Modulating the magnitude of the stimulus parameters affects the strength of the muscle contraction and coordinated functional movements can be generated by controlling the relative stimulation strengths of collections of muscles (Dobkin and Havton, 2004).

FES is used in multiple ways to improve function, including cardiovascular conditioning, improving gait control and speed, restoring hand control and breathing, and controlling bowel and bladder function. FDA has approved neuroprostheses for the restoration of hand function, bowel and bladder control, and breathing, and clinicians at many spinal cord injury centers are trained in their use. In addition, an FDA-approved walking system uses a nonimplanted FES and an FES cycle ergometric device that allow periodic exercise of paralyzed leg muscles.

As noted earlier in the chapter, electrical stimulation for bladder function control involves a neuroprosthesis sold in the United States as Vocare. It is an FDA-approved medical device that provides the user with the ability to void upon demand as a result of the stimulation provided by the implanted device. Electrodes are placed on the sacral roots either intradurally (which is the most popular location in Europe) or extradurally (which is the location used more frequently in the United States). Voiding of the bladder is controlled by an implanted radio receiver controlled by an external device that delivers energy and control to the implant. This system allows individuals with spinal cord injuries to manage difficult bladder problems and drain many urine management devices (catheters and condoms). It also reduces the incidence of bladder infections. The device has been implanted in more than 1,500 patients around the world, and 90 percent of those with the implant reportedly used it 4 to 6 days per week. Thus, the cost of the

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