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

Alexander T Brunfeldt; Barbara S Bregman; Peter S Lum

doi:10.3389/fnins.2024.1348103

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

Front Neurosci. 2024 Mar 4:18:1348103. doi: 10.3389/fnins.2024.1348103. eCollection 2024.

Authors

Alexander T Brunfeldt^{1

2

3}, Barbara S Bregman^{1

2}, Peter S Lum³

Affiliations

¹ Department of Rehabilitation Medicine, Georgetown University Medical Center, Washington, DC, United States.
² MedStar National Rehabilitation Network, Washington, DC, United States.
³ Department of Biomedical Engineering, The Catholic University of America, Washington, DC, United States.

Abstract

Background: 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.

Objective: Determine if corticospinal tract lesion load could explain individual differences in the responsiveness to exoskeleton loading of the arms in chronic stroke participants.

Methods: 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.

Results: Exoskeleton loading did not change RC (p = 0.07) or MC (p = 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 (R² = 0.43, p = 0.039); there was no such relationship for biceps MC (R² < 0.001, p = 0.98).

Conclusion: 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.

Keywords: electromyography; magnetic resonance imaging; neurorehabilitation; stroke; upper extremity.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. Research reported in this publication was supported by the National Center for Advancing Translational Sciences of the National Institutes of Health under Award Numbers UL1-TR001409, KL2-TR001432 & TL1-TR001431. This research also received funding from the National Institute of Child Health and Human Award Number 1F32HD108983 and National Institute on Disability, Independent Living, and Rehabilitation Research Award Number 90REGE0004. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.