Hemorrhagic transformation in ischemic posterior infarction by magnetic resonance imaging (MRI).

Purpose: To describe the incidence, time course, and clinical correlates of hemorrhagic transformation (HT) of ischemic stroke in the posterior cerebr al artery territory. Methods: Within 42 months 48 patients with 52 occipita l lobe infarctions were examined by T-1- and T-2-weighted MR imaging. The e xtent and distribution of secondary hemorrhage were analysed at different i ntervals after stroke. Volume of ischemic and hemorrhagic infarction was me asured planimetrically. Results: HT was observed in 71% of the infarcts bet ween the 5th day and up to 1 year after stroke. HT was most frequently (88% ) observed in the 2(nd) and 3(rd) month. HT was present in 55% of small inf arcts (<10 cm(3)), in 88% of medium size (10 - 50 cm(3)), and in all large (>50 cm(3)) infarcts. In 92% HT presented with petechial bleedings within t he cortex (64%) or less frequently (28%) in subcortical structures. The lat ter types of HT showed no progression and did not increase the clinical def icits. Space-occupying bleedings occurred in only two large defects. Conclu sions: In ischemic posterior infarction, HT can frequently be detected with in the first three months after stroke and is predominantly of the petechia l type and seems not to be relevant with regard to clinical deficits.