Epidural stimulation may help people with spinal cord injury develop functional connectivity and re-establish voluntary control of previously paralyzed muscles, investigators stated in research published online ahead of print April 8 in Brain. The therapy has the potential to change the prognosis of people with paralysis, even if it is administered years after injury, according to the authors.
In the study, four individuals with chronic complete motor paralysis were able to perform voluntary tasks while receiving epidural stimulation. Three of the participants recovered voluntary movement with epidural stimulation soon after implantation, and two of the three had complete loss of both motor and sensory function at study initiation. The results show “that by neuromodulating the spinal circuitry at subthreshold motor levels with epidural stimulation, chronically complete paralyzed individuals can process conceptual, auditory, and visual input to regain specific voluntary control of paralyzed muscles,” said Claudia A. Angeli, PhD. “We have uncovered a fundamentally new intervention strategy that can dramatically affect recovery of voluntary movement in individuals with complete paralysis even years after injury.”
Investigators Trained Four Patients With Paraplegia
The current investigation continues research that Dr. Angeli, Senior Researcher in the Human Locomotion Research Center at Frazier Rehab Institute in Louisville, and her colleagues began in 2009. In that trial, a young man paralyzed below his chest had a 16-electrode array implanted on his spinal cord. He underwent daily training in standing and walking, during which he was suspended over a treadmill while the array delivered electrical pulses to his spinal cord. The man became able to bear his own weight and stand without assistance for four minutes. At seven months, the man regained some voluntary control of his legs. Other impairments caused by the injury, such as of blood pressure control, body temperature regulation, bladder control, and sexual function, also began to improve over time in the absence of stimulation.
In the current study, Dr. Angeli and her colleagues implanted an epidural spinal cord stimulation unit and a 16-electrode array over the spinal cord in three additional participants with motor complete spinal cord injury. Participants’ average age at the time of implantation, including the patient who received implantation in 2009, was 27. All four patients were male, and their injuries had occurred at least two years before implantation. All individuals were unable to stand or walk independently or voluntarily move their lower extremities after their injuries.
After implantation, the investigators tested the individuals’ ability to move voluntarily with epidural stimulation. Participants underwent testing again after receiving intense stand training using epidural stimulation and after receiving intense step training in combination with epidural stimulation.
One Patient Performed Voluntary Movements Within a Week
All four individuals became able to move their legs intentionally in response to a verbal command. The first participant had no motor activity when he attempted to move without epidural stimulation following a verbal command, and the other three individuals had no motor activity when they attempted to move without epidural stimulation following a visual cue. All four individuals, however, generated electromyogram activity and movement during ankle dorsiflexion in the presence of epidural stimulation during their first experimental session, either before or after stand training.
At the start of the current study, the second person to receive implantation was unable to move or experience any sensation below the point of injury. This patient was able to perform voluntary movements during the first week of stimulation. The other patients recovered voluntary movement nearly as quickly as the second participant.
The speed at which each subject recovered may constitute evidence of dormant connections in patients with complete motor paralysis. “Rather than there being a complete separation of the upper and lower regions relative to the injury, it’s possible that there is some contact, but that these connections are not functional,” said V. Reggie Edgerton, PhD, Director of the Neuromuscular Research Laboratory at the University of California, Los Angeles. “The spinal stimulation could be reawakening these connections.”
All participants were able to synchronize leg, ankle, and toe movements in unison with the rise and fall of a wave displayed on a computer screen. Three individuals were able to change the force at which they flexed their leg, depending on the intensity of auditory cues. “The fact that the brain is able to take advantage of the few connections that may be remaining and then process this complicated visual, auditory, and perceptual information is pretty amazing,” said Dr. Edgerton. “It tells us that the information from the brain is getting to the right place in the spinal cord, so that the person can control, with fairly impressive accuracy, the nature of the movement.”