Robotic therapy for chronic stroke: general recovery of impairment or improved task-specific skill?

Abstract

There is a great need to develop new approaches for rehabilitation of the upper limb after stroke. Robotic therapy is a promising form of neurorehabilitation that can be delivered in higher doses than conventional therapy. Here we sought to determine whether the reported effects of robotic therapy, which have been based on clinical measures of impairment and function, are accompanied by improved motor control. Patients with chronic hemiparesis were trained for 3 wk, 3 days a week, with titrated assistive robotic therapy in two and three dimensions. Motor control improvements (i.e., skill) in both arms were assessed with a separate untrained visually guided reaching task. We devised a novel PCA-based analysis of arm trajectories that is sensitive to changes in the quality of entire movement trajectories without needing to prespecify particular kinematic features. Robotic therapy led to skill improvements in the contralesional arm. These changes were not accompanied by changes in clinical measures of impairment or function. There are two possible interpretations of these results. One is that robotic therapy only leads to small task-specific improvements in motor control via normal skill-learning mechanisms. The other is that kinematic assays are more sensitive than clinical measures to a small general improvement in motor control.

A Short and Distinct Time Window for Recovery of Arm Motor Control Early After Stroke Revealed With a Global Measure of Trajectory Kinematics

“…34 Furthermore, we have recently shown that our global kinematic measure can detect changes after robotic therapy in chronic stroke that were undetectable with either FMA-UE or ARAT. 22 Thus continuous 2-D kinematic data are in fact more sensitive to small differences in motor behavior than standard clinical measures. 22,33 Moreover, it is also highly unlikely that the AMD 2 improved in parallel with the clinical measures but went undetected.…”

“…22 Thus continuous 2-D kinematic data are in fact more sensitive to small differences in motor behavior than standard clinical measures. 22,33 Moreover, it is also highly unlikely that the AMD 2 improved in parallel with the clinical measures but went undetected. Analyses indicate >99% power to detect a change in AMD 2 of the same percent magnitude as was seen for the clinical measures beyond week 5.…”

“…Movement-start was defined as the time, before peak speed, when speed surpassed 2 cm/s. Movement-end was defined as the time, after peak speed, when speed remained below 2 cm/s for more than 0.1 s. As we have done previously 21,22,33 , in order to decrease contamination from target guesses, incomplete movements due to late reaction to target appearance, and involuntary movements due to failure to fully stabilize the arm in the starting position, we applied the following exclusion criteria: direction at peak speed ≥ 90° away from target direction, or ending ≤30% of target distance. However, for sake of completeness, we still conducted all analyses with the full dataset.…”

“…Details of this analysis have been reported previously and are provided in Supplemental Materials. 22,33 …”

Closed-Loop Task Difficulty Adaptation during Virtual Reality Reach-to-Grasp Training Assisted with an Exoskeleton for Stroke Rehabilitation

“…In severely affected patients, performance-dependent, neuromuscular electrical stimulation of individual upper limb muscles integrated in the exoskeleton may increase the range of motion even further (Grimm and Gharabaghi, 2016; Grimm et al, 2016b). These approaches focus on the improvement of motor control, which is defined as the ability to make accurate and precise goal-directed movements without reducing movement speed (Reis et al, 2009; Shmuelof et al, 2012), or using compensatory movements (Kitago et al, 2013, 2015). Functional gains in hemiparetic patients, however, are often achieved by movements that aim to compensate the diminished range of motion of the affected limb (Cirstea and Levin, 2000; Grimm et al, 2016a).…”