Reversible Ischemic Lesion Hypodensity in Acute Stroke CT Following Endovascular Reperfusion

BACKGROUND AND OBJECTIVES: In acute stroke, early ischemic lesion hypodensity on CT is considered the imaging hallmark of brain infarction, representing a state of irreversible tissue damage with a continual increase of net water uptake. This dogma, however, is challenged by rare cases of apparently reversed early lesion hypodensity after complete reperfusion. The purpose of this study was to investigate the occurrence of reversible ischemic edema after endovascular treatment.

METHODS: One hundred eighty-four patients with acute ischemic anterior circulation stroke were included after consecutive screening. Ischemic brain edema was determined with quantitative lesion net water uptake (NWU) in admission CT and follow-up CT based on CT densitometry, and ΔNWU was calculated as the difference. The association of edema progression to imaging and clinical parameters was investigated. Clinical outcome was assessed with the modified Rankin Scale (mRS) scores at day 90.

RESULTS: Of 184 patients, 27 (14.7%) showed edema arrest and 3 (1.6%) exhibited significant edema reversibility. Higher degree of recanalization (odds ratio [OR] 2.96, 95% confidence interval [CI] 1.46-6.01, p < 0.01) and shorter time from imaging to recanalization (OR per hour 0.32, 95% CI 0.18-0.54, p < 0.0001) were significantly associated with edema arrest or reversibility. Clinical outcome was significantly better in patients without edema progression (median mRS score 2 vs 5, p = 0.004).

DISCUSSION: Although rare, lesion hypodensity considered to be representative of early infarct in acute stroke CT may be reversible after complete recanalization. Arrest of edema progression of acute brain infarct lesions may occur after successful rapid vessel recanalization, resulting in improved functional outcome. Future research is needed to investigate conditions in which early revascularization may halt or even reverse vasogenic edema of ischemic tissue.