Abstract
Knowledge of spatiotemporal patterns of language network changes may help in predicting outcome in aphasic stroke patients. Here we assessed language function and performed functional MRI four times during one year to measure language network activation and cerebrovascular reactivity (with breath-holding) in twelve left-hemispheric stroke patients, of whom two dropped out before the final measurement, and eight age-matched controls. Language outcome was related to increase of activation in left and right posterior inferior temporal gyrus over the first year, while activation increase in right inferior frontal gyrus was inversely correlated to language recovery. Outcome prediction improved by addition of early language-induced activation of the left posterior inferior temporal gyrus to a regression model with baseline language performance as first predictor. Variations in language-induced activation in right inferior frontal gyrus were primarily related to differences in vascular reactivity. Furthermore, several language-activation changes could not be linked to alterations in language proficiency nor vascular reactivity, and were assumed to be caused by unspecified intersession variability. In conclusion, early functional neuroimaging improves outcome prediction of aphasia after stroke. Controlling for cerebrovascular reactivity and unspecified intersession variability may result in more accurate assessment of the relationship between activation pattern shifts and function after stroke.
Highlights
Each year, around 15 million people are affected by stroke worldwide[1]
Language (i.e. picture word matching (PWM))-related activation in the left and right posterior inferior temporal gyrus is related to improved language function, whereas activation in the right inferior frontal gyrus pars triangularis/ opercularis is inversely correlated to language recovery
In an earlier study we have shown that interpretation of the Functional MRI (fMRI) signal in the chronic phase after stroke is not confounded by altered vascular reactivity as measured through a breath hold paradigm[9], this may not hold for peri-lesional areas[38]
Summary
Around 15 million people are affected by stroke worldwide[1]. After dementia, it is the second leading cause of disability. We aimed to predict language outcome at one year in a group of aphasic stroke patients by applying fMRI in the subacute phase and assessing the contribution of different parts of the brain to language performance in the subacute to chronic phase after stroke. We hypothesized that (i) the extent of activity in left hemispheric language areas around two weeks after stroke as a predictor variable improves prediction of outcome at one year; (ii) the amount of language-induced activation in the left hemisphere is positively related to language performance, while activation of language areas in the right hemisphere is inversely related to language skill; and (iii) cerebrovascular reactivity and intersession variation of undetermined origin can confound the interpretation of changes of the fMRI signal over time
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