A surgically implanted nerve stimulation device, coupled with months of intensive training, has enabled two individuals with paralysis from traumatic injuries to walk independently years after losing all voluntary muscle control below the site of their spinal cord damage.
The details of this breakthrough "epidural stimulation" protocol – developed by teams from the Frazier Rehabilitation Institute and the University of Louisville Kentucky Spinal Cord Injury Research Center – were published today in the New England Journal of Medicine.
“It is incredible to be able to be in there and actually see them taking their first steps,” first author Dr Claudia Angeli told the Guardian. “It is an emotional time for the individual [themselves] because it is something that they have been told they are never going to be able to do again.”
Prior to their inclusion in the study, participants Kelly Thomas and Jeff Marquis had undergone conventional rehabilitation therapy for spinal cord injuries sustained in car and bike accidents, respectively, but remained unable to walk. Thomas had full use of her arms and Marquis had partial arm control, and both had retained slight sensation in their lower bodies.
Two other participants, also paraplegics but with no sensation below their injury sites prior to the investigation, were not able to walk without assistance after training with the device, yet they were able to stand and move their legs.
Though this treatment approach is still in its early days, these results further demonstrate that the framework of nerve connections necessary for voluntary movement is not completely destroyed by spinal cord trauma. Past research by the University of Louisville and other groups have shown that both implanted and subcutaneously applied electrodes can act as a bridge over the site of damage, connecting signals from the brain to the peripheral nerves that trigger muscles to contract. In recent human pilot studies, such devices have succeeded in restoring hand control in people with partial paralysis and leg movement in people with complete paralysis.
In the current investigation, Dr Angeli and her colleagues placed a 16-electrode array into the epidural space spanning the first lumbar vertebrae to the first or second sacral vertebrae; this was below each patient’s injury and encompassing the spinal cord regions that transmit signals to the legs. The stimulator control and battery were implanted into the abdominal wall, allowing for wireless remote control of the system.
After several weeks of testing to determine which combinations of electrodes were best suited to different leg and hip muscle movements, the grueling training regimen began. The four participants met with the researchers for two hours a day, five days a week, practicing mentally focusing on a particular movement while the corresponding stimulation pattern was active. Following 147 sessions, Thomas was able to walk on her own with a walker and stand for up to 50 minutes. Marquis, whose injury had been more severe, achieved independent walking with poles for balance after 278 sessions.
As of now, the participants’ regained movements are only possible when the electrodes are powered on. However, an earlier epidural stimulation patient under lead author Susan Harkema’s care was able to regain movement abilities without stimulation following more than 3.5 years of nervous system training.
“We must expand this research – hopefully, with improved stimulator technology – to more participants to realize the full potential of the progress we’re seeing in the lab, as the potential this provides for the 1.2 million people living with paralysis from a spinal cord injury is tremendous,” Harkema said in a statement.