For patients affected by paralysis resulting from spinal cord injury (SCI), head injury, stroke, or other neurological disorders, functional electrical stimulation (FES) can help restore function with the use of electrical currents. As we know, injuries to the spinal cord interfere with electrical signals between the brain and the muscles, resulting in paralysis below the level of injury. Although FES is also used for treatment of pain, pressure, and soreness prevention, restoration of limb and organ function are the main applications. In this article, we will explore how it is used in rehabilitation programs.

A BRIEF BACKGROUND

From a historical perspective, FES is considered a physiatric modality, although a growing interest in it for other fields has occurred since the mid-1970s in engineering, molecular biology, neurology, neurosurgery, orthopedics, physiology, plastic surgery, and urology. Each of these specialties appears to have embraced this treatment option, resulting in marked improvement in the technology available for functional applications.

The importance of FES as a modality in rehabilitation medicine continues to expand. Implantation of electrical stimulation systems goes back to the 1960s, but its therapeutic use for the management of spasticity has been traced back to the 1870s. Also worth noting:

• Modern phrenic nerve stimulation dates to 1948.
• Electrical stimulation has been utilized as a neural orthosis since 1961. Since that time, it has been an important adjunct in the rehabilitation of patients with hemiplegia, gait, and foot drop.
• Since the 1970s, FES for gait restoration after SCI has progressed from feasibility studies to the development of a commercially available, FDA-approved ambulation system.
• During the 1970s and 1980s, studies were initiated that examined the efficacy of FES in the management of scoliosis.

REHABILITATIVE APPLICATIONS

"The most common clinical applications of FES in the SCI/stroke population include standing or walking (for individuals with paraplegia or stroke)," says Lisa Boggs, PT, Cleveland FES Center, Louis Stokes VA Medical Center (http://fescenter.case.edu). "[Also for] grasp/release (tetraplegia); improved trunk control (tetraplegia or high paraplegia); restoration of bowel and bladder control; diaphragmatic control (high-level tetraplegia); and improvement of sexual function.

"The goal of FES is to produce useful movements that allow individuals with SCI or stroke to participate in meaningful activities," Boggs explains. "[It] helps to maximize function, independence, and quality of life." It provides options for negotiating architectural barriers; completing essential transfers (such as wheelchair to bed, car, or high surfaces, and bathroom transfers); allowing for short-distance mobility outside of the wheelchair, such as maneuvering through areas inaccessible by wheelchair; accessing items on high shelves or in cupboards that cannot be reached from the wheelchair or safely managed with reachers; allowing an individual to breathe without the use of a ventilator (diaphragm pacer); providing an individual with tetraplegia the use of their hand for function; and providing trunk control for individuals with trunk weakness. In addition:

• FES can decrease the need for caregivers by allowing increased independence for individuals with disability.
• The use of FES can prevent or even reverse some of the secondary conditions common after SCI by allowing users to exercise paralyzed muscles, which increases the blood flow to the muscle groups being exercised and can prevent or reverse a decline in function. Exercise and weight bearing can improve cardiovascular fitness and reduce osteoporosis without adverse effects on the joints. Preliminary studies also indicate that such exercise and weight bearing may reduce the risk of developing pressure ulcers by improving tissue oxygenation levels, increasing muscle bulk, and altering seated pressure distribution.
• Follow-up studies of FES system users have revealed a decreased frequency of pressure sores, lower-extremity spasticity, and urinary tract infections (UTIs), as well as decreased or no muscle atrophy.
• FES systems can be used for standing. Standing can prevent or reverse many of the detrimental effects of chronic immobility. The benefits of standing include increased bone mineral density/prevention of bone mineral loss (osteoporosis) of the lower extremities; decreased spasticity in the lower extremities; prevention of joint contracture or loss of ROM; improved skin condition/decreased risk of pressure sores due to pressure relief and improvement in circulation; decreased frequency of UTIs related to improved bladder function; decreased frequency of kidney stones; improved bowel function; psychological benefits such as improvement in self-esteem, self-image, and morale; and enhanced feelings of well-being and an improvement in quality of life (based on individual perception).

One of their patients, a C4 tetraplegic who had a system implanted to improve his trunk control, is now able to use the system when he is sitting in his wheelchair to give him a more upright seated posture. "We also were able to program a pattern that he can activate by elevating his shoulder using EMG that will sit him up if he were to have a loss of balance and be stuck in a forward-flexed position." In the past, he had been stuck in this position for several hours because no one was home to help sit him back upright. The system had allowed him to be able to do this independently. "We have several subjects who use the system to aid them when they are driving to help them maintain upright posture, especially when they would make a sharp turn," Boggs states. One woman uses the trunk system for recreation when she is sailing.

For standing they have several subjects who are using the system in their daily lives and in their work settings. One subject is an automobile mechanic, and the system has allowed him to be able to stand and work on cars again. Another woman uses the system to stand when she gives lectures for her business. "We have several subjects who have systems that allow them to ambulate with a reciprocal pattern," Boggs says. "Prior to getting the FES-implanted system, these individuals were unable to ambulate without using compensatory strategies. Now they are household and limited community ambulators."

Additionally, there are several subjects who have been able to benefit from the use of a grasp system. This allows them to be able to use their UE for function that would not be possible without FES. "The diaphragmatic control allows an individual to breathe without being on a ventilator. This will allow increased mobility options for these individuals," Boggs says.

FES has evolved very slowly in physical therapy programs, according to Boggs. "I haven't seen a lot of use of FES in PT departments due to time constraints and/or lack of equipment/training."

What's unique about the Cleveland FES program for patients is that there's really no other program like it that exists in this country. Having the system fully implanted is very unique. "The subjects get trained to use an implanted system that they can then continue to use on their own at home in order to increase their participation in family, work, or community activities," Boggs concludes.

TECHNICAL ASPECTS

Cleveland's FES Center has its own technology called the Implanted Stimulator Telemeter (IST) with a 10-, 12-, or 16-channel capability. "The circuit for that technology was developed around 1995," says John Uhlir, manager, Technical Development Laboratory. The technology is more than 20 years old now, and you couldn't buy one of these systems off-the-shelf back then. The PhD investigator at the time envisioned this system to help people with disabilities and wrote a grant to a funding agency to get the money to pursue the idea. "He's the one who developed it internally, and since then, some of the bigger companies have come up with their own multichannel implanted device," he says. A lot of those were developed after the early to mid-'80s, but the FES Center's first implant was placed in 1986.

The first application was a hand system to restore some function. Now they have taken that application and technology and used the lessons learned in implementing this into the lower extremities for a standing system. "You use the same implanted technology with eight electrodes on target muscles to get someone to close and open a hand, stand and sit from a wheelchair or from their car, van, or toilet," Uhlir says. "We position the arm in space so the hand is more useful, and we do that by implementing muscles in the shoulder," he explains. "It has gone from hand to leg to shoulder, and that's essentially where it is."

Uhlir started out on the clinical side where he took the hardware that was developed and built and put it into people that stood. He was on the standing team for a while, and after 15 patients—almost 5 years involved—it was ready to be commercialized. He came in to manage the group but is currently on the hardware delivery side to the PIs who put them into the patients. It's a new electrode technology that enables them to use a single electrode implanted on a nerve to get many different muscle activations, where in the past, it was a one-to-one match. "An electrode on one muscle, you get one muscle movement," he says. "To get another muscle movement means you need another electrode." They're doing more with each electrode, and that manifests itself on the front end in terms of current manipulation from the stimulator and information processing for commanding control. "In other words, there's a movement now in our community to get the entry in a more natural way. Rather than push a button to close your hand, you may activate a muscle in which you have voluntary control over and generate an EMG signal from within the body so it's transparent to the outside people." You move a muscle over which you have voluntary control. That signal is interpreted by the computer outside the body, and in real time the computer sends the implant and the appropriate signals to execute the next command. Let's say, "Elevate your shoulder slightly," and your hand will open. If you elevate it again, your hand will close, and it's because they've implemented EMG electrobiographic recording electrodes on the target muscle for that patient.

Theoretically, you could do this in the case of walking, Uhlir says. You could sense with an electrode what's happening on the bottom surface of the foot and use that as an input in the computer that could tell which muscles to fire or stimulate to get the right motion. "We're not there yet, but they are ideas we're talking about right now.

"In my opinion, one thing that seems to make sense," he continues, "is it has kind of exploded with the miniaturization of the electronics and with the computing power of the microprocessors. The more muscles you have to stimulate, the more coordination you're required to have." The timing becomes more critical, and if you're going to get many channels inside the body, you're going to need a small package. "With the concurrent development of smaller electronics and more powerful microprocessors, it has helped FES make significant jumps in the last 20, certainly 30 years," Uhlir notes.

PRODUCTS FOR UPPER EXTREMITIES

Bioness Inc (www.bioness.com), Ventura, Calif, has designed an advanced therapy system that uses mild electrical stimulation to improve the way a patient's arm works, helping an individual to get the most out of therapy and reduce complications, including muscle spasms. The NESS H200 Hand Rehabilitation System also may make it easier for a person to drink from a glass, reach for things, write, and use two hands again. It trains the hand so it may eventually work on its own.

Able to be put on and taken off with just one hand, the NESS H200 is for patients who have problems using a hand or arm due to stroke (hemiplegic), traumatic brain injury, SCI (C5 and C6), and other neurological disorders of the central nervous system such as Parkinson's disease and other upper motor neuron injuries. It is not, however, for patients with lower motor neuron disease or injury, those with arm dislocation or fracture, or pacemaker wearers.

The H200 has two main parts: the orthosis and the control unit. The orthosis attaches to the forearm and wrist and connects to the control unit. Inside the orthosis, electrodes deliver mild stimulation that helps the hand move. Large buttons and a rechargeable battery make it easy and convenient to use. The orthosis can be custom fit along with individualized setup of the control unit and then incorporated into a patient's therapy program. An initial fitting is required by the clinician.

FOR FOOT DROP

The NESS L300 is an advanced foot drop system that uses mild stimulation to lift a foot and help a patient walk more safely and easily on flat ground, up and down stairs, or on uneven surfaces. It is lightweight and fits just below the knee. It also can be put on and taken off with one hand and may eliminate the need for someone to wear a rigid, heavy orthosis.

Patients suffering from foot drop due to medical conditions resulting from stroke, traumatic brain injury, multiple sclerosis, cerebral palsy, incomplete SCI, and other neurological disorders of the central nervous system such as Parkinson's disease may benefit from using the L300. It is not for patients with peripheral nerve disease or injury such as Guillan-Barré Syndrome. Additionally, it should not be used by patients with certain types of pacemakers or implants, or those with fractures, dislocations, or cancer in the leg.

The L300 has three main parts that use wireless communication to "talk" to one another. The leg cuff is a small, lightweight device that fits just below the knee and contains electrodes that can be put where a patient needs it most for stimulation. The gait sensor attaches to the shoe and lets the leg cuff know if the heel is on the ground or in the air. The handheld remote control allows personal adjustment of stimulation. Again, an initial fitting is required by the clinician.

In addition to the above-mentioned products, Innovative Neurotronics (www.walkaide.com), Austin, Tex, offers the WalkAide, which can effectively counteract foot drop by producing dorsiflexion of the ankle during the swing phase of the gait. The small device attaches to the leg, just below the knee, near the head of the fibula. During a gait cycle, the WalkAide stimulates the common peroneal nerve, which innervates the tibialis anterior and other muscles that produce dorsiflexion of the ankle. It is appropriate for patients who have lost the ability to voluntarily lift their foot, often as a result of damage to the central nervous system from stroke, incomplete SCI, traumatic brain injury, cerebral palsy, and multiple sclerosis. This type of stimulation will not work for patients who have damage to the lower motor neurons/peripheral nerves.

The WalkAide is a battery-operated, single-channel electrical stimulator. It utilizes a tilt sensor to control stimulation during normal gait. A hand switch on the WalkLink is used by the clinician during setup to trigger stimulation while the heel sensor collects additional data. The clinician uses the WalkAnalyst software on a laptop computer to program the tilt sensor in the WalkAide. Use of the tilt sensor to trigger stimulation eliminates the need for external wires or a remote heel sensor during regular use.

Nina Silberstein is a contributing writer for Physical Therapy Products. For more information, contact .