Brain-Hand Function Relationships Based on Level of Grasp Function in Chronic Left-Hemisphere Stroke.
Elizabeth Rizor, Julius Fridriksson, Denise M Peters and 5 others
PMID 39162287WHAT IT FOUND
Hand function relates to different brain networks depending on severity.
In severe grasp impairment, contralesional connectivity matters most. In moderate impairment, corticospinal tract integrity predicts function. In mild impairment, neither motor connectivity nor tract integrity correlated with hand function.
Key findings
01In the Low grasp function group, contralesional resting-state functional connectivity was a significant predictor of hand function, whereas interhemispheric connectivity was not.
02Across the whole sample and in the Moderate group, corticospinal tract fractional anisotropy ratio was the primary predictor of hand function, not functional connectivity.
03In the High grasp function group, no measure of motor system functional connectivity or structural integrity significantly correlated with hand function.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
Cross-sectional design; cannot determine if brain measures cause functional differences or result from them. Small sample size in the Low group (N=12) limits statistical power for subgroup analyses. Data collected on two different MRI scanners without harmonization, which may have introduced variance. No age-matched control group, so it is unclear if findings in the High group reflect stroke-specific changes or normal variation. Results may not generalize to right-hemisphere stroke or acute/subacute recovery phases.
Declared interests
The authors declared no potential conflicts of interest. Funding was provided by the National Institutes of Health and the American Heart Association.
The easy way to misread this
Do not interpret the lack of correlation in the High group as evidence that brain function is irrelevant to mild hand deficits. This finding may reflect the insensitivity of the specific motor network measures used to capture subtle functional impairments in near-normal range performance.