Neuromotor Prosthetic to Treat Stroke-Related Paresis

Abstract

Background Functional recovery of independent arm movement typically plateaus within six months following a stroke, leaving survivors with chronic deficits. This feasibility study tested whether a wearable, powered exoskeletal orthosis, driven by a percutaneous, implanted brain-computer interface (BCI), using the ensemble activity of individual neurons in the precentral gyrus in the affected cortical hemisphere, could restore voluntary upper extremity function in a chronic hemiparetic stroke survivor. Methods One chronic hemiparetic stroke survivor with moderate-to-severe upper-limb motor impairment used a powered wearable elbow-wrist-hand orthosis that opened and closed the affected hand using cortical activity from the affected hemisphere with imagined hand movements. The system was evaluated in a home setting for 12 weeks. Motor function was evaluated before, during, and after the treatment. Results Robust single unit activity was present throughout the precentral gyrus areas implanted for the duration of the study. Although abnormal oscillations, that appeared to correlate with contralateral spasticity, were present, the participant was able to acquire voluntary control over a hand-orthosis BCI based upon ensemble single unit activity and high frequency local field potential power. The study participant (C2) was able to achieve a maximum score of 10 points on the Action Research Arm Test (ARAT) while using the BCI system as compared to 0 without any device, and 5 using only myoelectric control. Orthosis-powered hand-opening was faster with BCI-based control as compared to myoelectric control, likely due to the fact that BCI-control could be deployed without triggering abnormal spasticity inevitably reinforced by myoelectric control. Conclusions The findings demonstrate the therapeutic potential of an implantable BCI system targeting the affected hemisphere, to electrically bypass the stroke, in this n-of-1 pilot study. The ability of the participant to rapidly acquire voluntary control over otherwise paralyzed hand opening, more than 18 months after a subcortical stroke, lays the foundation for a fully implanted movement restoration system that could restore independent arm function to stroke survivors.