Defining Hypoperfusion in Chronic Aphasia: An Individualized Thresholding Approach.

Within the aphasia literature, it is common to link location of lesioned brain tissue to specific patterns of language impairment. This has provided valuable insight into the relationship between brain structure and function, but it does not capture important underlying alterations in function of regions that remain structurally intact. Research has demonstrated that in the chronic stage of aphasia, variable patterns of reduced cerebral blood flow (CBF; hypoperfusion) in structurally intact regions of the brain contribute to persisting language impairments. However, one consistent issue in this literature is a lack of clear consensus on how to define hypoperfusion, which may lead to over- or underestimation of tissue functionality. In the current study, we conducted an exploratory analysis in six individuals with chronic aphasia (>1 year post-onset) using perfusion imaging to (1) suggest a new, individualized metric for defining hypoperfusion; (2) identify the extent of hypoperfused tissue in perilesional bands; and (3) explore the relationship between hypoperfusion and language impairment. Results indicated that our individualized metric for defining hypoperfusion provided greater precision when identifying functionally impaired tissue and its effects on language function in chronic aphasia. These results have important implications for intervention approaches that target intact (or impaired) brain tissue.