Interhemispheric Pathways Are Important for Motor Outcome in Individuals with Chronic and Severe Upper Limb Impairment Post Stroke

Background: Severity of arm impairment alone does not explain motor outcomes in people with severe impairment post stroke. Objective: Define the contribution of brain biomarkers to upper limb motor outcomes in people with severe arm impairment post stroke. Methods: Paretic arm impairment (Fugl-Meyer upper limb, FM-UL) and function (Wolf Motor Function Test rate, WMFT-rate) were measured in 15 individuals with severe (FM-UL ≤ 30/66) and 14 with mild-moderate (FM-UL > 40/66) impairment. Transcranial magnetic stimulation and diffusion weight imaging indexed structure and function of the corticospinal tract and corpus callosum. Separate models of the relationship between possible biomarkers and motor outcomes at a single chronic (≥6 months) time point post stroke were performed. Results: Age (ΔR20.365, p = 0.017) and ipsilesional-transcallosal inhibition (ΔR20.182, p = 0.048) explained a 54.7% (p = 0.009) variance in paretic WMFT-rate. Prefrontal corpus callous fractional anisotropy (PF-CC FA) alone explained 49.3% (p = 0.007) variance in FM-UL outcome. The same models did not explain significant variance in mild-moderate stroke. In the severe group, k-means cluster analysis of PF-CC FA distinguished two subgroups, separated by a clinically meaningful and significant difference in motor impairment (p = 0.049) and function (p = 0.006) outcomes. Conclusion: Corpus callosum function and structure were identified as possible biomarkers of motor outcome in people with chronic and severe arm impairment

Spontaneous and Therapeutic-Induced Mechanisms of Functional Recovery After Stroke

With increasing rates of survival throughout the past several years, stroke remains one of the leading causes of adult disability. Following the onset of stroke, spontaneous mechanisms of recovery at the cellular, molecular, and systems levels ensue. The degree of spontaneous recovery is generally incomplete and variable among individuals. Typically, the best recovery outcomes entail the restitution of function in injured but surviving neural matter. An assortment of restorative therapies exists or is under development with the goal of potentiating restitution of function in damaged areas or in nearby ipsilesional regions by fostering neuroplastic changes, which often rely on mechanisms similar to those observed during spontaneous recovery. Advancements in stroke rehabilitation depend on the elucidation of both spontaneous and therapeutic-driven mechanisms of recovery. Further, the implementation of neural biomarkers in research and clinical settings will enable a multimodal approach to probing brain state and predicting the extent of post-stroke functional recovery. This review will discuss spontaneous and therapeutic-induced mechanisms driving post-stroke functional recovery while underscoring several potential restorative therapies and biomarkers