There has been another epidural stimulation breakthrough. This time, a study shows three incomplete quads are now able to walk, and two of them can use a walker in their community. All three have regained some functional improvements — even with the stimulator turned off. The Switzerland-based study, published on Oct. 31 in Nature, comes on the heels of two other studies — one from the University of Louisville and one from the Mayo Clinic — demonstrating the power of epistim to restore some walking abilities.
The major advancement of the Switzeland study, led by Swiss Federal Institute of Technology’s Grégoire Courtine, is the method used to apply electrical stimulation to participants’ spinal cords. Previous studies used a continuous stream of stimulation, which Courtine’s team found may block some signals traveling from the legs to the brain, interfering with users’ ability to know where their limbs are in space without looking at them. Called proprioception, this ability is a key component of functional movement.
To address this possible signal blocking, the Swiss researchers mapped when and where in the spinal cord signals are sent to tell the legs to walk. The team then programed the stimulators to mimic these patterns and more closely resemble the natural firing of the spinal cord. Their findings indicate that this method may promote functional recovery of previously paralyzed muscles in a way that continuous stimulation does not.
The U.S. trials featured months of preparatory loco-motor training to prime the participants’ muscles and nervous systems before the stimulators were implanted. The Swiss study did away with the preparatory rehab. But once implanted, their stimulators still produced near immediate results. Within a week of beginning the patterned stimulation all three participants were able to walk with some of their body weight supported.
As shown in the above gif, the walking achieved by the trial participants is not a fluid gait like you would see in a nondisabled person. It requires effort and concentration. Also, the post-trial outcome is linked to the level of a participant’s residual pre-stimulation function. However, like in the U.S. studies, after the stimulators were implanted, the Swiss participants continued to make functional improvements through months of intense physical therapy and gait training with the stimulators activated.
According to an editorial that accompanied the Nature paper, the patterned stimulation protocol, “also enabled the individuals to regain control over previously paralyzed muscles when electrical stimulation was turned off. This indicates that the brain and spinal cord had re-established functional connections, revealing an unexpected degree of plasticity.”
The caveat of this study is that the participants all had motor-incomplete injuries. More research is needed to determine how this patterned stimulation will affect those with motor-complete SCI and those with varying levels of sensation. Furthermore, the patterned stimulation has only been used to facilitate the muscular functions associated with walking.
But given the procedure’s initial success, it will be exciting to see how this advancement could be used to treat other complications of SCI, including cardiovascular, bowel and bladder, sexual and upper-extremity function, all of which epidural stimulation has already been shown to improve.
Lead photo courtesy of: EPFL / Jean-Baptiste Mignardot