Abstract T P30: Logarithmic Growth of Ischemic Lesions in Major Anterior Circulation Ischemic Strokes

Abstract

Purpose: To analyze the dynamics of diffusion lesion volumes within the first 48 hours after stroke onset in patients with major anterior circulation occlusions (ACOs). Methods: Diffusion ischemic lesion volumes were serially measured in 50 patients that had MRI performed at baseline (~4 hours post ictus) and 2 or 3 additional MRI exams (~12, ~24, ~48 hours post ictus). Thirty eight of these patients had documented major ACOs (terminal internal carotid or proximal middle cerebral artery). Average rate of lesion growth was calculated at each time interval. Functional outcomes (3-month modified Rankin Scale) were correlated to admission NIHSS, DWI volumes and initial lesion growth rates. Results: DWI lesion growth in ACOs was nonlinear over 48 hours and exhibited a logarithmic pattern. The lesion growth rates were highest during earliest period (11.4 ml/hr) and declined during at the 5-12 (0.8 ml/hr ), 12-24 (1.9 ml/hr) and 24-48 hour (0.9 ml/hr) periods. In 23/38 patients there was little or no growth during 5-12 hours period despite continued presence of occlusion in over half of these patients. However, 12/38 experienced >30% growth of lesion during this period, with nearly all patients having persistent occlusions. Functional outcomes correlated with baseline NIHSS and DWI lesion size, as well as initial average growth rate, but only the latter was an independent predictor Conclusions: The growth of ischemic DWI lesions caused by occlusion of major anterior circulation arteries is nonlinear and typically logarithmic. The rate of growth at the earliest time period is a strong predictor of functional outcomes. There is high variability in growth rates due to site of occlusion and most likely the quality of collateral flow. Our results have implications for "Time is Brain."