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Skilled Reach Performance Correlates With Corpus Callosum Structural Integrity in Individuals With Mild Motor Impairment After Stroke: A Preliminary Investigation

Background. Recovery of arm function after stroke is often incomplete. An improved understanding of brain structure–motor behavior relationships is needed for the development of novel and targeted rehabilitation interventions. Objective. To examine the relationship between skilled reach performance and the integrity of two putative white matter motor pathways, corticospinal tract and corpus callosum, after stroke. Methods. Eleven individuals with chronic stroke (poststroke duration, mean 62.5 ± 42.4 months) and mild motor impairment (upper extremity Fugl-Meyer score, mean 54.2 ± 7.6) reached to six targets presented at three distances and two directions. Fractional anisotropy (FA) obtained from diffusion tensor imaging was used to determine the structural integrity of the corticospinal tract and the corpus callosum. Results. Overall reach performance was decreased in the paretic arm compared with the nonparetic arm. While FA was decreased in the ipsilesional corticospinal tract, FA in the corticospinal tract did not correlate with variability in reach performance between individuals. Instead, FA in the premotor section of the corpus callosum correlated with reach performance; individuals with higher FA in premotor corpus callosum tended to reach faster with both the paretic and nonparetic arms. Conclusions. The structural connections between the two premotor and supplemental cortices that traverse the premotor corpus callosum may play an important role in supporting motor control and could become a target for interventions aimed at improved arm function in this population.