Non-invasive zaps to the spinal cord can treat paralysis—but no one knows why

With a zap of electricity from well-placed electrodes on the back of the neck, patients with tetraplegia can regain some modest yet potentially “life-changing” functioning of their hands and arms, according to data from a small clinical trial published Monday in Nature Medicine.

The relatively simple stimulation method—which requires no surgery—offers an accessible, more affordable, non-invasive means for those living with paralysis to regain some meaningful function, the researchers behind the trial say. However, the therapy’s further potential remains limited given that scientists have yet to fully understand exactly why it works.

For the trial, 60 patients with tetraplegia underwent the stimulation therapy over at least 24 sessions during a two-month period. At the end, 72 percent (43 patients) saw clinically meaningful improvements in both strength and functional performance. Further, 90 percent (54 patients) saw improvement from at least one strength or functional outcome. There were no serious adverse events reported.

“The most exciting thing for us is that we’re seeing effects that improve quality of life,” Chet Moritz, a co-author of the study and co-director for the Center for Neurotechnology at the University of Washington, said in a press briefing. “And also, we believe that the stimulation may be causing neuroplasticity or, in a sense, healing part of the damage to the spinal cord injury, such that the benefits persist beyond stimulation.”

The trial, which took place at 14 clinical sites across the US, Canada, and Europe, was a prospective study—not the gold-standard design of a randomized, double-blind placebo control trial. Moritz and his colleagues explained that there were a number of reasons for this. For one, they weren’t sure if they could use a sham electrical stimulation for a placebo group. Patients can feel the real electrical stimulation, described as an internal “buzz,” and efforts to re-create the feeling, but not the effects of a sham treatment, were uncertain. Also, there were ethical concerns about having people with tetraplegia repeatedly travel to clinical sites and be subjected to potentially uncomfortable treatments with no expected benefit.

Still, the researchers behind the study are confident that the gains they saw were not simply placebo effects. For one thing, all the trial participants spent two months in standard rehabilitation therapy before they underwent the stimulation therapy. And their progress in that first phase of the trial was compared to their progress in the second half, in which they received the therapy. The differences were “very dramatic for many of the measures,” Edelle Field-Fote, a co-author and Director of Spinal Cord Injury Research at Shepherd Center in Georgia, said in the briefing.