Abstract Number: Esoc2026a1045 Temporal Dynamics of Dwi Lesion Volume in Acute Stroke and Its Clinical Relevance

Abstract Background and aims While infarcts are known to expand after stroke onset, the clinical relevance of quantitative DWI lesion volume dynamics in a large ischemic stroke cohort remains under-investigated. Methods We analyzed 8,576 consecutive patients from a prospective registry with paired DWI scans (baseline 24h; follow-up 24–168h). Lesion volumes were automatically quantified. Predictors of lesion change were evaluated using robust linear and quantile regression. Associations between lesion change and 3-month modified Rankin Scale (mRS) were assessed via ordinal logistic models. We utilized counterfactual mediation analyses to quantify the mechanistic role of volume dynamics and estimated the volume change corresponding to the minimal clinically important difference (MCID) for 3-month mRS. Results Median DWI volume increased from 0.74mL to 1.51mL (median absolute increase 0.38mL; relative +49.2%). Predictors of greater growth included higher baseline NIHSS (ß±SE, 0.36±0.02), early neurological deterioration (1.12±0.09), endovascular treatment (1.43±0.22), and larger baseline DWI volume (0.36±0.02). Larger volume increases were independently associated with worse 3-month outcomes (cOR and 95% CI, 0.39 0.32–0.46 for the fifth versus second quintile). However, mediation analyses through volume dynamics were statistically detectable but quantitatively limited. MCID analyses indicated that DWI volume change required to achieve clinically meaningful outcome shifts (2.18mL 2.5th–97.5th percentile interval, 1.07–4.46 for a 5% probability increase) was substantially larger than changes observed in routine care. Conclusions Although DWI lesion growth is common and associated with worse outcomes, mediation and MCID analyses suggest that lesion volume changes have limited utility as standalone surrogate biomarkers for clinical endpoints. Conflict of interest All authors have nothing to disclose. Figure 1 - belongs to Results Table 1 - belongs to Results