A clinical trial to study changes in neural activity and motor recovery following brain-machine interface enabled robot-assisted stroke rehabilitation

Abstract

Abstract Background Brain-machine interfaces (BMI) based on scalp electroencephalography (EEG) have the potential to promote cortical plasticity following stroke, which has been shown to improve motor recovery outcomes. However, clinical efficacy of BMI-enabled robotic rehabilitation in chronic stroke population is confounded by the spectrum of motor impairments caused by stroke. Objective To evaluate the efficacy of neurorehabilitation therapy on upper-limb motor recovery, by quantifying changes in clinical, BMI-based, and kinematics-based metrics. Further, to identify neural correlates or biomarkers that can predict the extent of motor recovery. Methods Chronic stroke survivors (n = 10, age 55 ± 9.2y, chronicity 3.1 ± 2.8y) were recruited to participate in a 4-6 weeks long clinical study. Participants completed 12 therapy sessions that involved a BMI enabled powered exoskeleton (MAHI Exo-II) for training, which targeted elbow flexion and extension. Clinical assessments including Fugl-Meyer Upper Extremity (FMA-UE) and Action Research Arm Test (ARAT) were measured up to 2-months after therapy. BMI performance, kinematic performance, and change in movement related cortical potentials (MRCP) were also determined. Results On average, 132 ± 22 repetitions were performed per participant, per session. BMI accuracy across all sessions and subjects was 79 ± 18%, with a small number of false positives (23 ± 20%). FMA-UE and ARAT scores improved significantly over baseline after therapy and were retained at follow-ups (ΔFMA-UE = 3.92 ± 3.73 and ΔARAT = 5.35 ± 4.62, p < 0.05). 80% participants (7 with moderate-mild impairment and 1 with severe-moderate impairment) reached minimal clinically important difference (MCID: FMA-UE > 5.2 or ARAT > 5.7) during the course of the study. Kinematic measures indicate that, on average, participants’ movements became faster and smoother. Quantification of changes in MRCP amplitude showed significant correlation with ARAT scores (ρ = 0.72, p < 0.05) and marginally significant correlation with FMA-UE (ρ = 0.63, p = 0.051), suggesting higher activation of ipsi-lesional hemisphere post-intervention. The study did not have any adverse events. Conclusion This study presents evidence that BMI enabled robotic rehabilitation can promote motor recovery in individuals with chronic stroke, several years after injury and irrespective of their impairment level, or location of the lesion (cortical/subcortical) at baseline. Further, the extent of motor recovery was correlated with changes in movement related potentials, occurring contralateral to the impaired arm. Support NIH National Robotics Initiative Grant R01NS081854 and a grant from Mission Connect, a project of TIRR Foundation.