Promising Movement After Severe
Spinal Cord Injury
(continued from the front page)
This exciting news could mean that patients may not have to rely solely on the regrowth of nerves in order to regain function. Most promising is the fact that the results were observed in all four patients, suggesting a real phenomenon is at play here. The participants were all able to voluntarily flex toes, ankles and knees while the stimulator was active, and the movements were enhanced over time when combined with daily physical therapy. The researchers are optimistic that the new therapy has the potential to change the prognosis of people with paralysis even years after injury.
As noted, another impressive finding of the study is that two of the patients who benefited from the spinal stimulation had complete motor and sensory paralysis. In these patients, the pathway that sends information about sensation from the legs to the brain is disrupted, in addition to the pathway that sends information from the brain to the legs in order to control movement. Until now assumptions were that at least some of the sensory pathway needed to be intact for the therapy to be effective.
The researchers write: “Previously, we reported that one individual who had a motor complete, but sensory incomplete spinal cord injury regained voluntary movement after 7 months of epidural stimulation and stand training. We presumed that the residual sensory pathways were critical in this recovery. However, we now report in three more individuals voluntary movement occurred with epidural stimulation immediately after implant even in two who were diagnosed with a motor and sensory complete lesion.” They deem this new effort “a fundamentally new intervention strategy” that can dramatically affect recovery of voluntary movement.
In 2009 a related pilot trial attempted to determine whether spinal stimulation, in conjunction with daily training on a treadmill, could help patients with paralysis regain some ability to move. During the intervention, a patent paralyzed from the chest down had a 16-electrode array implanted on his spinal cord. He then underwent daily training suspended in a harness over a treadmill while a team of researchers supported his legs, helping him to either stand or walk. At the same time, the array delivered electrical pulses to his spinal cord just below his injury.
The group was trying to increase the sensitivity of local circuits within the spinal cord that carry out basic motor functions without input from the brain—hence the external electrical stimulation. The team never thought the stimulation would be strong enough on its own to initiate muscle activation, but reasoned that combined with sensory input from stepping on a treadmill, the electrode array could lead to movement. Seven months into the trial, the patient discovered that he had regained some voluntary control of his legs. Interestingly, in the absence of continued stimulation, the injury began to improve over time. The present follow-up study finds the three additional patients with paralysis recovering voluntary muscle control following the electrical stimulation of the spine.
All participants can now synchronize leg, ankle and toe movements in unison with the rise and fall of a wave displayed on a computer screen, and three out of the four were able to change the force at which they flexed their leg. The researchers report in their results, “We demonstrate that neuromodulating the spinal circuitry with epidural stimulation, enables completely paralysed individuals to process conceptual, auditory and visual input to regain relatively fine voluntary control of paralysed muscles.”
After several months of spinal stimulation, patients carried out home-based training, which consisted of hour-long stimulation while practicing intentional movements lying down. At the end of the training, some subjects were able to execute voluntary movements with greater force (and with reduced stimulation), while others experienced enhanced movement accuracy. The ability to develop “functional connectivity” across the lesion of their injuries leads to important questions regarding when and if someone should be diagnosed as clinically motor complete. It certainly appears that locomotor training is vital to the rehabilitation process, and speaks volumes about the plasticity of the human body, even in the face of once seemingly insurmountable adversity.