From Paralysis to Recovery

Spinal electrical neuromodulation alone has been shown to produce positive results in UL motor recovery in individuals with cervical SCI or stroke. However, the combination of TSS and hand grip training and its potential effects on sensorimotor functions has not been investigated thoroughly. Sayenko hypothesized that combining these two in cervical SCI or stroke populations would enhance hand function beyond what is seen in participants receiving TSS alone or hand grip training alone. “This study presents preliminary evidence from individuals with spinal cord injury and stroke that continuous TSS delivered over the cervical spinal cord, in combination with task-specific hand grip training, resulted in notable improvements in maximum hand grip strength in the trained upper limb,” said Sayenko. “The results of our case series showed that individual interventions, either TSS or hand grip training, exhibited limited effectiveness in improving grip strength. Furthermore, to our knowledge, this is the first demonstration of TSS modulating the cervical spinal networks to specifically improve impaired grip strength after stroke.” Study participants included four individuals with cervical SCI and two individuals with cerebral stroke. The SCI participants had a chronic injury with the neurological level of injury at or between C4-C7. The stroke participants had either ischemic or hemorrhagic stroke. This subject-blinded, cross-over design study included two four-week interventions with sessions performed thrice a week. Sessions entailed repetitive proximal and distal task-specific movements with or without subsequent hand grip training. Sayenko and his team evaluated hand grip force using a handgrip dynamometer and visual feedback from electromyography.

For this study, Sayenko used neurophysiological stimulators conventionally utilized in research. Self-adhesive electrodes connected to a constant-current stimulator from Digitimer Ltd, UK were placed on the skin to deliver TSS. Wireless surface electromyography electrodes from Trigno Avanti (Delsys, USA) were used to record signals from four UL muscles (flexor carpi radialis, extensor carpi radialis, first dorsal interosseous and abductor pollicis brevis). Participants were verbally encouraged to apply maximum grip force during testing of the maximum voluntary contraction. Sayenko added, “TSS has the potential to improve hand control, hand grip force production and dexterity in individuals with SCI. TSS combined with task-specific hand grip training may involve different and perhaps synergistic processes leading to more effective reorganization of neural circuits. Further research is needed to determine the optimal stimulation parameters to target specific motor pools and to engage movements in specific upper limb joints of interest throughout the training process.” Currently, Sayenko and his team are engaged in several clinical trials to test the efficacy of TSS in regaining various UL movements after paralysis. Further investigations along the lines of the findings in this study, with a larger sample size, would enhance our understanding of SCI pathophysiology and effective therapies that promote neuronal recovery and patient outcomes.