Spinal Cord Injuries : Muscle Stimulators, Drug Treatment

by Food and Drug Administration (FDA)

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Muscle Stimulators

Muscle stimulators using electrical currents that stimulate muscles to contract, especially FES systems (functional electrical stimulation), have been the focus of much media attention. Some FES systems under development are enabling paralyzed people to walk again. Such systems operate as a kind of complex prosthetic device, meaning that although the stimulation can cause muscles to contract and legs to move, it is a kind of "artificial" walking, since no actual movement has been regained by the patient and there is no sensation of movement.

Other FES systems stimulate nerves to give hand movement so quadriplegic individuals without hand function can feed themselves. But FES systems are not without drawbacks: They aren't for everyone, they're costly and still largely experimental, and surgery to implant electrodes is required, which can pose possible complications.

Stimulators aren't just for walking or movement. For example, FDA-approved phrenic nerve stimulators allow people with high-level spinal cord injuries to breathe without respirators. (The phrenic nerve goes from the spinal cord to the diaphragm, and activating it causes the diaphragm to contract). But again, there are use limitations; the phrenic nerve has to be healthy. Robert F. Munzner, Ph.D., chief of FDA's neurological devices branch, estimates that only a few hundred people nationwide can use the device.

According to Marie A. Schroeder, a physical therapist and chief of FDA's restorative devices branch, many muscle stimulators have been cleared for marketing, but not specifically for functional purposes.

"For example, if some muscles are not totally paralyzed and doctors want to see how much improvement in movement or feeling someone will get, they may use a stimulator to maintain range of motion to help provide muscle reeducation, until they see how much voluntary control the patient gains," she explains. "But using stimulators for functional purposes gets into the investigational area. The only functional use of a muscle stimulator that has been cleared are those stimulators that might be used for a patient with a localized nerve injury- -for example, a patient who can't lift his foot up. However, we consider the stimulation of muscles needed for the purpose of walking to be investigational."

Physicians surveyed say electrical stimulation is not being widely used on a routine basis because the technology is not yet "user-friendly." William O. McKinley, M.D., director of spinal cord injury and rehabilitative medical services at The Medical College of Virginia, notes that devices that assist paralyzed patients in coming to a standing position, for example, are "very expensive, very time-consuming to learn, and usefulness has to be determined on a patient-by-patient basis."

Many other uses of stimulators are not common or remain investigational. For example, although stimulators that offer pain prevention and electro-ejaculation to collect sperm to enable paralyzed men to become fathers are used clinically, their use is not widespread.

F. Terry Hambrecht, M.D., head of the neural prosthesis program at the National Institutes of Health's National Institute of Neurological Disorders and Stroke, says such systems are still technologically limited, but he is optimistic about the future.

"The problem now is that we're in the Model-T stage. We don't yet have the sophistication and reliability we need," he admits. "But there's no doubt in my mind that eventually functional stimulation devices will be developed for spinal cord-injured patients. We're funding quite a few projects for people who are paralyzed."

Hambrecht says one current project involves electrode implantation to restore bladder and sexual function to paralyzed men and women. He anticipates the first implants will be done within five years.

Drug Treatment

Muscle stimulators have provided drama, but the steroid methylprednisolone, experts say, has actually changed the face of clinical treatment for people with spinal cord injuries. A recent report of a 1985 to 1989 study of 487 patients, funded by the National Institute of Neurological Disorders and Stroke, showed that patients given high doses of this cortisone-like drug within eight hours of injury regained an average of 20 percent of lost motor and sensory function. Experts cite the study as the first evidence that a medication can improve the outcome of spinal cord injury, and today the drug is widely used for acute spinal cord injury.

Surgeons use the potent drug, which was approved some years ago by FDA as an anti-inflammatory agent and is also approved to treat swelling around the brain, to manage acute attacks of multiple sclerosis and for a variety of allergic conditions.

Wise Young, M.D., Ph.D., part of the methylprednisolone study team, is a professor of neurosurgery, physiology and biophysics and director of the neurosurgery research lab at New York University Medical Center. Young points out that the drug does not enable patients to immediately "leap out of bed." Beneficial effects are usually not apparent until at least six weeks after the drug is administered. Yet he believes the use of the drug is a landmark development.

"It has changed the attitude of doctors toward spinal cord injury. They no longer see it as a hopeless condition, and patients are rushed to hospitals earlier," he explains. "It also has tremendous implications for chronic spinal cord injury, since the finding that you only need a few axons to get function back means you don't have to regenerate as many axons."

"Currently there are over two dozen drugs reported to be neural-protective in animals," Young says. "The leap that was made in 1990 was between absolutely no hope to some hope. There is a real sense of optimism now; it's not a matter of if, but when, a drug will be available to aid regeneration of the spinal cord."

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.