Defining Hypoperfusion in Chronic Aphasia: an Individualized Thresholding Approach

EasyChair Preprint 6467

Abstract

Individuals with chronic aphasia (IWA; >1yr) exhibit variable patterns of language impairment, which may be due to underlying alterations in brain function. Prior research shows that IWA have reduced cerebral blood flow (CBF; hypoperfusion) in structurally intact brain areas. However, there is little consensus on how to best define hypoperfusion. Two issues are at play: standard CBF threshold values do not fully capture tissue functionality, and group-level analyses may overshadow important individual differences. Using an individualized metric for hypoperfusion, we investigated 1. when functionally compromised perilesional tissue returned to normal CBF levels; 2. how our metric correlated with auditory comprehension. Language assessments for 6 monolingual IWA were conducted with the BDAE-3 and WAB-R. Anatomical and rs-CBF data were co-registered and labeled and 4 LH perilesional bands were created (0-3mm, 3-6mm, 6-9mm, 9-12mm). Group- and individual-level analyses were performed on CBF patterns in LH-perilesional bands and specific regions of interest. “Normal” CBF was based on each participant’s average RH CBF (CBF_RH); “functionally compromised” tissue was anything 1.5 SDsRH. Results: 1) Both group and individual analyses showed hypoperfusion in the 0-3mm band, but only the individual-level analyses revealed differences for if and when CBF values returned to normal in the remaining 3 bands and picked up on hypoperfusion in ROIs that remained structurally intact. 2) Only individualized thresholding revealed a correlation between auditory comprehension and multiple temporal regions (as compared to using the standard CBF metrics). Results suggest that our individualized approach is better at identifying functionally compromised tissue and underscores the importance of considering both structural and functional integrity of brain regions when investigating structure-function relationships.

Keyphrases: Chronic Aphasia, Perfusion Imaging, Perilesional Tissue, Stroke, cerebral blood flow, hypoperfusion, individual differences, language behavior

@booklet{EasyChair:6467,
  author    = {Noelle Abbott and Carolyn Baker and Conan Chen and Thomas Liu and Tracy Love},
  title     = {Defining Hypoperfusion in Chronic Aphasia: an Individualized Thresholding Approach},
  howpublished = {EasyChair Preprint 6467},
  year      = {EasyChair, 2021}}