Improved Motor Function via Non-Invasive Stimulation of the Spinal Cord

Injuries to the spinal cord are severe and can leave its victims physically impaired. In the past, these injuries have been treated through surgeries or medications. These methods are either invasive and risky or are temporary solutions that do not directly address the limited motor control resulting from the injury. However, recent studies have shown that non-invasive stimulation of the spinal cord can improve motor function in patients suffering from spinal cord injury. 

In the article “Corticospinal-motor neuronal plasticity promotes exercise-mediated recovery with humans with spinal cord injury,” Dr. Perez observed how the recovery rate when exercise is paired with non-invasive stimulation at spinal synapses compares to the rate with normal exercise in patients with spinal cord injury (SCI). Non-invasive stimulation was performed through paired corticospinal-motor neural stimulation (PCMS) in individuals with injuries to the cervical, thoracic, or lumbar regions of the spinal cord. A total of 38 individuals with SCI participated in this subject and were randomly assigned to one of three treatment groups. Exercise paired with PCMS was the treatment method for the first group, exercise paired with sham-PCMS for the second, and only PCMS for the third. Each of these groups completed ten sessions using their designated treatment method with muscle stimulation being measured through motor evoked potentials (MEP). Each muscle tested was stimulated to approximately 50% of the MEP-max amplitude, and the level of maximal voluntary contraction (MVC) was measured via EMG activity. Results showed that MEP and MVC both increased in the PCMS paired with exercise and the PCMS only groups while the sham-PCMS group did not display a change in MEP or MVC. The participants in each group were then reassessed after six months. The performance of the participants in the PCMS paired with exercise and the PCMS only groups remained the same, whereas the sham-PCMS group decreased in performance. 

In her study, Dr. Perez showed that non-invasive stimulation combined with exercise is a viable method for promoting recovery in patients with SCI. The article “Spinal direct current stimulation (tsDCS) in hereditary spastic paraplegias (HSP): A sham-controlled crossover study” by Dr. Adrolino et. al mentions a similar study in which non-invasive stimulation through transcutaneous spinal direct current stimulation (tsDCS) was used to reduce spasticity in individuals with HSP. Eleven participants with HSP were divided into two groups: one would be receiving anodal tsDCS while the other would be receiving sham-tsDCS (the control group). The researchers measured the differences in performance between the groups using MEP, H-reflex, F-waves, Ashworth scale (measures spasticity), the Five Minutes Walking Test, and the Spastic Paraplegia Rating Scale (SPRS). In both of the groups, the H-reflex, F-waves, and MEP remained constant and there was no difference observed with the Five Minutes Walking Test and SPRS. However, there was a notable decrease in the score on the Ashworth scale for the anodal tsDCS group. Therefore, it was concluded that anodal tsDCS is an effective technique in decreasing spasticity and allowing for less constricted movements in HSP patients. 

The two studies utilized different methods of non-invasive stimulation of the spinal cord to improve motor function. Dr. Perez was able to determine that PCMS was effective in increasing the recovery rate for patients with SCI based on the observations of improved motor functionality immediately after treatment and after the six months follow-up assessment. Dr. Adrolino was able to prove that tsDCS can significantly decrease spasticity in HSP patients, which can also be applied to patients with SCI or other neurodegenerative diseases that impair movement. With the findings presented in these studies and many other studies alike, non-invasive stimulation can advance and become even more successful in the treatment of motor-impaired individuals.  

Citations

Perez, Monica A., and Hang Jin Jo. “Corticospinal-Motor Neuronal Plasticity Promotes Exercise-Mediated Recovery in Humans with Spinal Cord Injury.” Brain, vol. 143, no. 5, 2020, pp. 1368–1382., doi:10.1093/brain/awaa052. 

Ardolino, Gianluca, et al. “Spinal Direct Current Stimulation (TsDCS) in Hereditary Spastic Paraplegias (HSP): A Sham-Controlled Crossover Study.” The Journal of Spinal Cord Medicine, 2018, pp. 1–8., doi:10.1080/10790268.2018.1543926.