Non-invasive spatiotemporal spinal neuromodulation targeting dorsal roots improves paretic leg motor control during walking in persons with stroke.

Abstract

Individuals post-stroke demonstrate impaired motor control and muscle weakness in the paretic leg interfering their mobility. We aimed to determine whether applying spatiotemporally controlled transcutaneous spinal cord stimulation (tSCS), when combined with constraint force induced forced use (CIFU), enhances paretic leg motor control during walking in individuals post-stroke. Thirteen individuals with stroke (age: 64.2 ± 7.1 years old; time post stroke: 14.1 ± 6.1 years) were tested in a crossover design under two conditions: active vs sham tSCS during CIFU treadmill walking (tSCS+CIFU vs sham+CIFU). In both conditions, CIFU treadmill walking was performed with constraint force applied to the non-paretic leg during swing phase of gait. For the active condition, tSCS was delivered at L4 during the swing phase (80 Hz) and at S1 during the stance phase (30 Hz) of the paretic leg, filled with a carrier frequency of 9.5 kHz. Spatiotemporal gait parameters, muscle activity, and propulsive force were assessed. Participants showed greater increases in paretic step length and step height in the tSCS+CIFU condition compared to the sham+CIFU condition, while showed prolonged paretic stance time in both conditions. The tSCS+CIFU condition also showed significantly less foot path variability of the paretic leg compared to sham+CIFU. Muscle synergy analysis revealed increased muscle weightings in plantarflexion, dorsiflexion, and hip/knee extension synergies of the paretic leg in both conditions. Propulsive force of the paretic leg showed no change in both conditions. In conclusion, applying spatiotemporally controlled tSCS during CIFU treadmill walking may enhance paretic leg motor control in individuals post-stroke.