Chronic post-stroke aphasia severity is determined by fragmentation of residual white matter networks

Many stroke survivors with aphasia in the acute period experience spontaneous recovery within the first six months after the stroke. However, approximately 30–40% sustain permanent aphasia and the factors determining incomplete recovery are unclear. Suboptimal recovery may be influenced by disruptio...

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Bibliographic Details
Published in:Scientific reports 2017-08, Vol.7 (1), p.8188-13, Article 8188
Main Authors: Marebwa, Barbara K., Fridriksson, Julius, Yourganov, Grigori, Feenaughty, Lynda, Rorden, Chris, Bonilha, Leonardo
Format: Article
Language:English
Subjects:
631/378/116/1925
631/378/2649/1594
692/617/375/534
Aphasia
Attention deficit hyperactivity disorder
Brain architecture
Community structure
Hemispheric laterality
Humanities and Social Sciences
multidisciplinary
Neural networks
Science
Science (multidisciplinary)
Spontaneous recovery
Stroke
Substantia alba
Temporal lobe
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Summary:Many stroke survivors with aphasia in the acute period experience spontaneous recovery within the first six months after the stroke. However, approximately 30–40% sustain permanent aphasia and the factors determining incomplete recovery are unclear. Suboptimal recovery may be influenced by disruption of areas seemingly spared by the stroke due to loss of white matter connectivity and network integrity. We reconstructed individual anatomical whole-brain connectomes from 90 left hemisphere stroke survivors using diffusion MR images. We measured the modularity of the residual white matter network organization, the probability of brain regions clustering together, and the degree of fragmentation of left hemisphere networks. Greater post-stroke left hemisphere network fragmentation and higher modularity index were associated with more severe chronic aphasia, controlling for the size of the stroke lesion. Even when the left hemisphere was relatively spared, subjects with disorganized community structure had significantly worse aphasia, particularly when key temporal lobe regions were isolated into segregated modules. These results suggest that white matter integrity and disorganization of neuronal networks could be important determinants of chronic aphasia severity. Connectome white matter organization measured through modularity and other topological features could be used as a personalized variable for clinical staging and aphasia treatment planning.
ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-017-07607-9