September 24, 2018
Regaining the ability to walk after experiencing a spinal cord injury may be possible with a combination of rehabilitation methods, new research suggests.
Even after several years of living with complete motor paralysis, two participants in the study were able to achieve the goal of independent walking following a combined regimen of intensive locomotor exercises and spinal cord stimulation. Two other participants experienced partial gains.
Recovery took commitment and time, note the investigators. One participant with a mid-cervical spine injury achieved "over ground" walking, that is, not on a treadmill, after gait training for 85 weeks and 278 sessions of programmed epidural spinal cord stimulation. The other independent walker suffered damage to their mid-thoracic spine and performed over ground walking after 15 weeks of intense standing and stepping exercises and 81 stimulation sessions.
"The take-home message is that when provided with the appropriate information, the spinal cord has the capacity to relearn the task of walking in individuals with motor complete injury, even years after injury," principal investigator Claudia A. Angeli, PhD, Frazier Rehabilitation Institute and Kentucky Spinal Cord Injury Research Center in Louisville, told Medscape Medical News.
"We trained our research participants to stand for 1 hour and step for an additional hour a day, 5 days a week. This training does not differ from those receiving multiple rehab interventions or even training to play a sport," Angeli added.
The study was published online September 24 in the New England Journal of Medicine.
Spinal Stimulation Essential
The researchers built on their previous findings (Brain. 2014;137:1394-1409), which demonstrated that simultaneous intense rehabilitation and epidural stimulation can restore some volitional movement below the level of a spinal cord injury. A previous case report in The Lancet (2011;377:1938-1947) also suggested this combination could help patients regain the ability to stand on their own.
The four participants in the current study began the protocol 2.5 to 3.3 years following their injury. They were unable to stand, walk, or move their legs voluntarily following conventional clinical rehabilitation. The investigators assessed motor function by scoring their ability to move five joints, from C5 to T1 motor segment on the arms and from L2 to S1 on their legs.
Their ability to sense a pinprick or light touch varied. The researchers again scored each participant's response to these sensations bilaterally on each arm and leg.
After the patients received intense locomotor training for 8 to 9 weeks, they still could not stand or walk independently over ground or on a treadmill. Each then received a programmed epidural stimulator, a 16-electrode array (Medtronic) implanted over spinal segments L1 to S1 or S2. They also had a spinal cord stimulator placed surgically in the anterior abdominal wall.
Over ground walking only occurred with spinal cord stimulation and the participant's intention to walk.
"This suggests that interneuronal networks in the lumbosacral spinal cord may be activated by the electrical stimulation through dorsal nerve roots and by direct stimulation of the parenchyma of the cord," the researchers note.
In addition, electromyography demonstrated activation of neurons in the spinal cord, ruling out an effect based on the frequency of the stimulation alone.
The two more successful participants required an assistive device for over ground walking.
Although the two remaining participants failed to perform over ground walking after 159 sessions and 176 sessions, respectively, they were able to stand and sit independently.
One of these participants experienced the only adverse event in the study — a spontaneous hip fracture. The fracture occurred when he was stepping on the treadmill with bodyweight support after 1 week of training. He did not fall and resumed the training 1 year later.
Persons with some degree of spared sensation below the level of injury may be more suitable candidates than those with no sensation, the researchers note. However, this hypothesis and the durability of over ground walking will require investigation in larger groups of patients with spinal cord injury, they add.
"This research was done in a small number of individuals," Angeli said. She and her colleagues are planning the next steps in their research.
"We need to be able to reproduce these results in a larger cohort. We also have a lot to learn about spinal cord plasticity and learning following spinal cord injuries," Angeli concluded.
Also asked to comment on the study, Anand Pandyan, PhD, professor of rehabilitation technology and head of the School of Health and Rehabilitation at Keele University in the United Kingdom, told Medscape Medical News, "The treatment involves the implantation of an electrode array on relevant section of the spinal cord to stimulate the muscles essential for walking, and then providing an intensive period of task-specific rehabilitation to the patients.
"What seems interesting is that a person is able to learn to drive the system automatically after this period of intensive training, and they are able to activate the appropriate muscles," he said. Given that these patients have an incomplete lesion with no measurable motor response, as measured using an insensitive clinical scale, does not mean that they have no motor drive at all, he added. Additional research is warranted to explore this further.
"For many years, scientist have attempted to use electrical stimulation to facilitate walking and cycling in patients with spinal cord injury. We have had varying levels of success, but clinical implementation has been a problem," Pandyan said. "This new method may have solved a barrier to clinical implementation, and further studies are needed."
The study was supported by the Leona M. and Harry B. Helmsley Charitable Trust. Medtronic supplied the implantable devices but had no other role in the research. Angeli had reported no relevant financial relationships.