Adjusting the body’s motor reflexes could improve mobility in patients with incomplete spinal cord injuries

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According to a study published in the Journal of Neuroscience, patients with incomplete spinal cord injuries who underwent a training programme that taught them how to adjust their motor reflexes (reflex control) saw improvements in walking

During training, the participants were instructed to suppress a knee jerk-like reflex elicited by a small shock to the leg. Those who were able to calm hyperactive reflexes—a common effect of spinal cord injuries— saw improvements in their walking.


The study was led by Aiko Thompson and Jonathan Wolpaw, both of whom hold appointments at the New York state Department of Health and the State University of New York in Albany, and at Columbia University in New York City. It took place at Helen Hayes Hospital in West Haverstraw, N. Y. It was funded in part by NIH’s National Institute of Neurological Disorders and Stroke (NINDS).

“People tend to think of reflexes as fixed, but in reality, normal movement requires constant fine-tuning of reflexes by the brain. Loss of that fine-tuning is an important part of the disability that comes with a spinal cord injury,” said Wolpaw, a research physician and professor at the Wadsworth Center, the state health department’s public health laboratory.

The study involved 13 people who were still able to walk after incomplete spinal cord injuries that had occurred from eight months to 50 years prior to the study. All had spasticity and an impaired ability to walk. The goal was to determine if these individuals could gain mobility by learning to suppress a spinal H-reflex, which is elicited by electrical stimulation rather than by a tendon stretch. H-reflexes are routinely measured for diagnosing nerve disorders and injuries, but this is the first study to examine whether consciously modifying an H-reflex can help people with spinal cord injuries.

Participants in the study received electrical stimulation to the soleus (calf muscle) of their weaker leg while standing with support. The first two weeks of the study involved baseline measurements of the resulting reflex. During the next 10 weeks, nine participants underwent three training sessions per week, during which they viewed the size of their reflexes on a monitor and were encouraged to suppress it. A control group of four participants received the stimulation but no feedback about their reflexes. Before and after these sessions, the researchers measured the participants’ walking speed over a distance of 10 meters, and monitored their gait symmetry with electronic shoe implants.

Six of the nine participants in the training group were able to suppress their reflexes. Their walking speed increased by 59 percent on average, and their gait became more symmetrical. These improvements in speed and symmetry were not seen in three participants who were unable to suppress their reflexes, or in the control group. Many participants also spontaneously told the researchers they were noticing improvements in daily living activities. About 85% of these comments came from people who were able to control their reflexes after several weeks of training.

Because this was a small study, a larger multicentre trial would be necessary to assess the clinical benefits of the therapy.

In addition to grants from NINDS (NS069551, NS022189 and NS061823), this study was funded by the NYS Spinal Cord Injury Research Trust (C023685) and the Helen Hayes Hospital Foundation.

 

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