Presentation
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Fiber Length, Aphasia Severity, & Cognition
Poster E60 in Poster Session E, Thursday, October 26, 10:15 am - 12:00 pm CEST, Espace Vieux-Port
Rebecca Roth1, Natalie Busby2, Janina Wilmskoetter3, Chris Rorden2, Roger Newman-Norlund2, Julius Fridriksson2, Leonardo Bonilha1; 1Emory University, 2University of South Carolina, 3Medical University of South Carolina
Introduction: Severity of post-stroke aphasia and cognitive function is typically predicted by lesion size and location followed by age at stroke; however, there is unexplained variance when considering these factors. Previous work shows that the health of spared tissue, i.e., structural network integrity, plays a role in both aphasia severity and recovery trajectories. Specifically, fiber length has been shown as a predictor of aphasia severity (as measured by the Western Aphasia Battery) and as a mechanism of aphasia recovery (naming improvements) 1,2. There is evidence showing that long-range fibers are particularly susceptible to injury due to their metabolic load, and long-range fibers may be a particularly useful measure of structural network integrity in individuals with cerebrovascular events like stroke 3,4. Methods: In this study, we examined 88 participants with chronic aphasia (> 12 months post-stroke) following a left hemisphere stroke. Participants were tested for aphasia severity and cognition, including the following tests at baseline: Western Aphasia Battery- Revised (WAB)5, Philadelphia Naming Test (PNT)6, Pyramids and Palm Trees Test (PPTT)7, and the Matrix Reasoning subtest from the Wechsler Intelligence Test8. Participants also underwent T1, T2, and diffusion weighted imaging at baseline. This allowed us to create an individualized structural connectome for each participant, calculate Euclidean distance between each pair of ROIs in the Johns Hopkins University Atlas, and categorize fibers as short, medium, and long in length. We then computed a ratio of long to short range fibers normalized by total number of fibers in order to measure structural network integrity. Multiple linear regression were then run to examine the relationship between baseline variables and structural network integrity. Results: Structural network integrity, lesion volume, and age, explained 37.2% in WAB-AQ (F=16.56, p<.001), 32.3% in WAB Naming (F=13.27, p<.001), 31.2% in WAB Repetition (F=12.71, p<.011), 30% in WAB Comprehension (F=11.99, p<.001), 34.3% in WAB Spontaneous Speech (F=14.61, p<.001), 30.1% of correct items on the PNT (F=12.06, p<.001), 14.9% for correct items on the PPTT, and 25.5% on the Matrix reasoning subtest (F=4.89, p<.004). Discussion: Our results demonstrate that non-lesioned tissue, i.e., structural network integrity, is an important predictor of aphasia severity and cognitive function in individuals with chronic post-stroke aphasia. Our results fit with previous work indicating structural network integrity and fiber length as important predictors of aphasia severity and recovery1,2 and extend these results by examining a ratio of long to short fibers across several behavioral measures. Overall, we demonstrate the importance of white matter structural integrity in relation to aphasia severity and cognition.
Topic Areas: Disorders: Acquired,