Since the spinal cord is critical in signaling voluntary movements from the brain, spinal cord injuries often result in paralysis. Although previous studies have shown that repetitive stimulation over a course of two weeks can improve voluntary movements of people with spinal cord injuries, Health Day reported an early study recently found that a non-invasive technique improved movement after a single session and could help patients regain use of their hands in the future.
Monica Perez, assistant professor of physical medicine and rehabilitation at the University of Pittsburgh School of Medicine, along with her colleague, Karen Bunday, conducted a study to see if they could improve movement control in patients with injuries. The pair used two forms of non-invasive nerve stimulation for the study.
First, study subjects received electrical stimulation of the ulnar nerve in the wrist. In the second form of stimulation, an electromagnetic coil was placed near the scalp and created electric currents to stimulate the nerves connected to hand function. Using this transcranial magnetic stimulation (TMS), the researchers were able to target the corticospinal tract, which plays “a major role in the recovery of motor function in spinal cord injury,” according to Perez.
Nineteen people with spinal cord injuries that had partially damaged their ability to move and feel their arms and hands were selected for the study. They also tested the effects on 14 healthy people. Participants received 100 paired electrical pulses over 20 minutes.
Researchers found that the timing of the stimulation was crucial. Electrical pulses from the brain needed to be precisely timed to arrive at the spinal cord one or two milliseconds before pulses from the wrist nerve. Effects lasted up to 80 minutes, and Bunday notes that after 17 minutes of stimulation, they saw an increase in muscle activity and force of between 20 and 40 percent.
Although the timing factor needs to be individualized for each patient, the study is the first to show that a single session of the non-invasive technique could help improve movement. The results of the study are promising for patients with spinal cord injury and could eventually lead to the development of portable devices that people could use at home to stimulate nerves and improve muscle function. Perez, however, notes that more research needs to be done to assess the long-term effects: “We’re trying to understand the mechanisms of this plasticity, and how we can make these changes more permanent.”