be intact for the therapy to be effective.
The study is the continuation of a groundbreaking pilot trial initiated in 2009 to determine whether spinal stimulation, in conjunction with daily training on a treadmill, could help patients with paralysis regain some ability to move. In that trial, Rob Summers, a young man paralyzed below his chest, had a 16-electrode array implanted on his spinal cord. He then underwent daily training in which he was 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.
According to the researchers, the goal of the stimulation was to increase the sensitivity of local circuits within the spinal cord that carry out basic motor functions without input from the brain—such as the knee jerk that occurs after stepping on a tack, or even more complex patterned movements like stepping. While not strong enough to directly induce muscle activation by itself, the researchers believed the stimulation could lead to movement when combined with sensory input from stepping on a treadmill.
With his stimulator active, Summers was able to gradually bear his own weight and could eventually stand without assistance from physical therapists for up to four minutes. Surprisingly, seven months into the trial, Summers also discovered that he had regained some voluntary control of his legs. The researchers were amazed by this latter outcome, as intentional movement requires information to travel from the brain down to the lower spinal cord, a path that had been rendered nonfunctional by his injury. Other impairments caused by Summers’ injury also began to improve over time, in the absence of stimulation, such as blood pressure control, body temperature regulation, bladder control, and sexual function.
Now, in this follow-up study, Claudia Angeli, Ph.D., assistant professor at the University of Louisville’s Kentucky Spinal Cord Injury Research Center and her research colleagues report that three additional patients with paralysis have recovered voluntary muscle control following electrical stimulation of the spine. Their report, which also includes results from new tests conducted on Summers, was published in the April 8 online issue of Brain.
The three patients in the new study include two with complete motor and sensory paralysis, and one, similar to Summers, with complete motor paralysis but some ability to experience sensation below his injury. Within just a few days of the start of stimulation, all three patients regained some voluntary control of previously paralyzed muscles.
The first person they implanted after Summers was unable to move or experience any sensation below his injury and was initially meant to be their baseline patient. “What was astounding about him was that not only was there voluntary movement, but we saw it in the first week of stimulation. We then saw it in the next two patients as well,” said Susan Harkema, Ph.D., the director of rehabilitation research at the Kentucky Spinal Cord Injury Research Center at the University of Louisville, and a researcher in the study.
The researchers point to the speed at which each subject recovered voluntary movement as evidence that there may be dormant connections that exist 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, Ph.D., a UCLA distinguished professor of integrative biology and physiology, and the researcher responsible for developing the novel approach to rehabilitation. “The spinal stimulation could be reawakening these connections.”
An important aspect of the new study involved assessing the ability of each patient to modulate his movements in response to auditory and visual cues. "We hoped to determine if they could voluntarily move in the presence of stimulation, and als