AUTHOR=Brunfeldt Alexander T. , Bregman Barbara S. , Lum Peter S. 

TITLE=Responsiveness to exoskeleton loading during bimanual reaching is associated with corticospinal tract integrity in stroke

JOURNAL=Frontiers in Neuroscience

VOLUME=18

YEAR=2024

URL=https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2024.1348103

DOI=10.3389/fnins.2024.1348103

ISSN=1662-453X

ABSTRACT=<sec id="sec1"><title>Background</title><p>Device-based rehabilitation of upper extremity impairment following stroke often employs one-sized-fits-all approaches that do not account for individual differences in patient characteristics.</p></sec><sec id="sec2"><title>Objective</title><p>Determine if corticospinal tract lesion load could explain individual differences in the responsiveness to exoskeleton loading of the arms in chronic stroke participants.</p></sec><sec id="sec3"><title>Methods</title><p>Fourteen stroke participants performed a bimanual shared cursor reaching task in virtual reality while exoskeletons decreased the effective weight of the more-impaired arm and increased the effective weight of the less-impaired arm. We calculated the change in relative displacement between the arms (RC) and the change in relative muscle activity (MC) between the arms from the biceps and deltoids. We calculated corticospinal tract lesion load (wCSTLL) in a subset of 10 participants.</p></sec><sec id="sec4"><title>Results</title><p>Exoskeleton loading did not change RC (<italic>p</italic> = 0.07) or MC (<italic>p</italic> = 0.47) at the group level, but significant individual differences emerged. Participants with little overlap between the lesion and corticospinal tract responded to loading by decreasing muscle activity in the more-impaired arm relative to the less-impaired arm. The change in deltoid MC was associated with smaller wCSTLL (<italic>R</italic><sup>2</sup> = 0.43, <italic>p</italic> = 0.039); there was no such relationship for biceps MC (<italic>R</italic><sup>2</sup> &lt; 0.001, <italic>p</italic> = 0.98).</p></sec><sec id="sec5"><title>Conclusion</title><p>Here we provide evidence that corticospinal tract integrity is a critical feature that determines one’s ability to respond to upper extremity exoskeleton loading. Our work contributes to the development of personalized device-based interventions that would allow clinicians and researchers to titrate constraint levels during bimanual activities.</p></sec>