Postmortem MR imaging of lobar cerebral infarction with pathologic and in vivo correlation.

Postmortem magnetic resonance (MR) imaging features of different types of lobar cerebral infarction are correlated with the findings in gross and histologic specimens. The postmortem findings are also correlated with in vivo findings in similar cases selected from teaching files. In acute infarction, white matter vasogenic edema leads to high signal intensity on T2-weighted images and blurring of the gray-white matter junction. Petechial hemorrhage in the cortex results in inhomogeneous signal intensity on T2-weighted images. In laminar necrosis, the hyperintense cortex on T1-weighted images is due not to hemorrhage but possibly to necrosis and the presence of lipid-laden macrophages. In subacute infarction, cortical edema and necrosis may cause the gyral pattern of enhancement. Meningeal inflammation and early fibrosis are probably responsible for meningeal enhancement. In chronic infarction, gliosis and cystic malacia are responsible for the increased signal intensity of white matter on T2-weighted images. Knowledge of the pathologic features of cerebral infarction helps in understanding the MR imaging findings.