White matter microstructure in language tracts in youth with perinatal stroke.

Perinatal strokes occur more commonly in the left hemisphere and often impact language areas, yet language disability only occurs in a small proportion of cases. Functional imaging studies investigating language processing have shown that perinatal stroke in the left hemisphere may result in contralesional shifts of activity, but none have investigated the structure of white matter connections in such altered language network conditions. Diffusion tensor imaging and neurite orientation dispersion and density imaging offer robust, microstructurally-sensitive metrics which can richly characterize tracts known to support language function. In a sample of 105 participants aged 6 to 19, 73 participants with perinatal stroke and 32 typically-developing controls, we applied these techniques to evaluate differences in microstructure of the arcuate fasciculus and uncinate fasciculus, two tracts classically associated with language, following perinatal stroke while controlling for age, sex, and lesion volume. We identified widespread differences in microstructure in both hemispheres for the arcuate and uncinate fasciculi in perinatal stroke participants compared to controls. Subtypes of perinatal stroke presented differently, with arterial ischemic stroke lesions showing more structural differences than periventricular infarction lesions. Differences between perinatal stroke subtypes were observed for both tracts in both hemispheres. Overall, we demonstrate that white matter microstructure of bilateral language networks is impacted by unilateral perinatal stroke. These bilateral differences in white matter structure after unilateral injury suggest that neuroplastic mechanisms may operate in both hemispheres during development with possible functional implications that could inform customized patient-centered rehabilitation strategies.