We were excited to read the research reports about the four men who took part in a study looking at the effects of epidural stimulation on voluntary movement following a spinal cord injury. Voluntary movement requires a message from the brain to travel down long pathways of the spinal cord to communicate with nerves at different levels in the spinal cord. The spinal cord nerves, following stimulation from the nerves in the long pathways, innervate muscles to cause a voluntary contraction.
A spinal cord injury interrupts the long pathways from the brain to the spinal cord, limiting or preventing messages from the brain from reaching the nerves in the spinal cord. If the nerves in the spinal cord are not receiving the messages from the brain, they will not voluntarily innervate the muscles to cause a contraction. The nerves in the spinal cord below the level of the injury are intact, yet they are not receiving information from the brain and can almost become de-sensitized to information.
Epidural stimulation is being used to increased excitability, or sensitivity, of the spinal cord nerves to make them more sensitive, and receptive, to any input that may still be attempting to travel along the pathways from the brain. A spinal cord stimulator is implanted in the abdomen and electrodes are implanted in the epidural space of the lower thoracic and upper lumbar regions of the spinal cord. A remote control is used to turn on and off the stimulator. The electrodes do not cause muscle contractions but excite the nerves in the spinal cord, making them more receptive to messages from the brain. With time, the stimulation may cause changes in the activity of the spinal cord nerves, making them receptive to input not only while the stimulator is turned on, but also when it is off.
The recent study, published in the journal Brain, reports findings demonstrating the recovery of some voluntary movement in the lower extremities of four men with complete spinal cord injuries following the implantation and use of epidural stimulation. The specific changes that occurred as a result of the epidural stimulation have not yet been identified, but researchers are working on several neurophysiological and neuroanatomical theories.
Although this is a small study, it clearly demonstrates that the spinal cord has the ability to regain some function following an injury. Epidural stimulation for voluntary muscle contraction is still in the experimental stage, yet is a promising strategy, when used in conjunction with other rehabilitative techniques, that is worth paying attention to!