Regional lesion burden and chronic post-stroke aphasia severity: Incremental value beyond total lesion volume

We examined whether regional lesion burden adds information beyond clinical variables and total lesion volume regarding chronic aphasia severity. This secondary analysis of the Aphasia Recovery Cohort included 195 participants with left-hemisphere stroke, Western Aphasia Battery Aphasia Quotient (AQ) ≤93.8, and assessment ≥180 days after stroke. Lesion burden was quantified in five atlas-defined groups. Partial Spearman correlations were adjusted for age at stroke, sex, time to assessment, and lesion volume, and four ridge-regression models were compared using 30 repetitions of five-fold cross-validation. A sensitivity analysis included participants whose imaging and Western Aphasia Battery assessments were ≤90 days apart (n = 128). Dorsal white-matter burden remained associated with lower AQ after adjustment (partial ρ = -0.261; false-discovery-rate q = 0.002). Adding regional burdens to the clinical-plus-volume model increased mean cross-validated R² from 0.306 to 0.384 (ΔR² = 0.078) and reduced mean absolute error from 18.76 to 17.31 AQ points. In the time-restricted sample, R² increased from 0.312 to 0.442 (ΔR² = 0.130), with the dorsal association persisting (partial ρ = -0.307). Regional lesion burden adds information beyond lesion volume and supports anatomical characterization of chronic aphasia severity.