Abstract W P166: Asymmetrical Fractional Anisotropy Correlates with Verbal Fluency Task Performance at Different Stages Post-stroke
Objective: Diffusion tensor imaging (DTI) can be used to quantify integrity of the white matter (WM) tracts by calculating the fractional anisotropy (FA) within a region of interest. Following stroke, unilateral reductions in integrity of tracts involving language function give rise to interhemispheric asymmetries in FA values. Here, we explored the relationships between asymmetrical FA measures and their ability to predict performance in verbal fluency tasks at different post-stroke stages.
Methods: DTI data were acquired axially from 21 stroke patients at acute stage, 19 at sub-acute stage and 12 at chronic stage in a GE 3T MRI scanner. FOV = 25.6 cm х 25.6 cm, acquisition matrix = 256 х 256, slice thickness = 2 mm, number of slices = 75, number of diffusion directions = 56. Data were processed using FSL. FA values of language tracts were calculated-superior longitudinal fasciculus (SLF), sagittal stratum (SS, including inferior longitudinal fasciculus and inferior fronto-occipital fasciculus) and Uncinate fasciculus (UF). Asymmetrical FA (aFA) was computed for the affected and unaffected SLF, SS and UF in order to measure the asymmetry of WM integrity: aFA= (FAunaff - FAaff)/( FAunaff + FAaff), which yields a value between -1.0 and +1.0, where positive values indicate reduced FA in the affected WM tracts, and a value of 0 indicates symmetricial FA in the tracts. aFA was correlated with patient behavior in language task-verbal fluency (VF) with subject outliers outside of the 95% confidence interval removed.
Results: At acute stage, higher values of aFA in SLF (R2 = 0.606, p = 0.008) and SS (R2 = 0.624, p = 0.004) were significantly correlated with poor VF performance. At sub-acute stage, higher values of aFA in SS (R2 = 0.431, p = 0.028) were inversely correlated with poor VF performance. At chronic stage, higher values of aFA in SLF were inversely correlated with poor VF performance (R2 = 0.517, p = 0.008).
Conclusion: Results show that asymmetries in white matter tract integrity (i.e., SLF, SS and UF), generally considered as language-function tracts, are significantly correlated with verbal fluency performance at different stages post-stroke, implying changes in WM integrity in these tracts over time may lead to changes in behavioral performance.
Author Disclosures: J. Song: None. V.A. Nair: None. C. La: None. J.A. Sattin: None. V. Prabhakaran: None.
This research has received full or partial funding support from the American Heart Association, Midwest Affiliate – Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, South Dakota, Wisconsin.
- © 2014 by American Heart Association, Inc.