Spinal Cord Injury Research: Epidural Stimulation Research Progressing

Source: Christopher & Dana Reeve Foundation

By Sam Maddox

We reported last summer that several more young men with spinal cord injuries have been surgically implanted with electrical stimulator units. The devices, off-the-shelf products made for pain relief, are placed over the lower part of the spinal cord, in the lumbar area. The concept is this: the spinal cord contains an intricate weave of nerve fibers that, when properly activated, are able to control certain motor functions. This control occurs without any input from the brain; this means the spinal cord itself is, to a degree, able to remember and to execute. The cord is “smart.” In recent years research scientists have been able to exploit this smartness, using aggressive exercise protocols and, more recently, electrical impulses, to activate the lumbar circuitry.

Support the weight of an infant with his or her feet on the ground and the baby will begin taking alternating steps, left-right-left. How is this done? Not fully by brain input; that system has not fully formed. The stepping motions are organized in the spinal cord by way of what scientists call a central pattern generator (CPG). If the spinal cord receives the right information from the sensory system – e.g. weight bearing or perhaps in the form of weight bearing on a treadmill, or Locomotor Training (LT) – the CPG responds by initiating step patterns by itself.

Many animal experiments, and more recently, a limited number of human trials, have shown that activating the CPG can have important benefits. Some people have regained walking function; almost all participants in the LT program of the Reeve Foundation NeuroRecovery Network (NRN), have gained meaningful health benefits.

Two years ago an international team of researchers funded mainly by the Reeve Foundation raised the ante in boosting CPG response. A small electrical array was implanted over the dura of the lumbar cord. The first patient with the epidural stimulator had no motor function below his chest-level injury. When the lumbar cord was stimulated, however, he could stand on his own and take steps. To the surprise of the research team, the young man regained voluntary motor function when the stim was on. What was even more surprising, he regained bladder control and sexual function, even when the stim was off. Not only was the CPG reawakened, it seemed to remain awake. We’re talking, of course of Rob Summers, who is no stranger to readers of this website.

This epidural stimulation work – overseen at Frazier Rehab Institute in Kentucky by Susan Harkema, Ph.D., director of the NRN, and based to a large degree on the research of Reggie Edgerton, Ph.D., at UCLA – has continued. So far, four patients have been fitted with epidural stimulators. While the data have not yet been published, all four have shown similar patterns of recovery: they can step when the stim is on. They all gained muscle mass, improved cardiovascular function and were able stand with no assistance with the stimulator on.

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