Two histological methods for recognition and study of cortical microinfarcts in thick sections

Cortical microinfarcts are the most widespread form of brain infarction but frequently remain undetected by standard neuroimaging protocols. Moreover, microinfarcts are only partially detectable in hematoxylin- eosin-stained (H&E) 4-10 μm paraffin sections at routine neuropathological examination. In this short report, we provide two staining protocols for visualizing cortical microinfarcts in 100-300 μm sections. For low-power microscopy, the first protocol combines aldehyde fuchsine staining for detection of lipofuscin granules and macrophages with Darrow red counterstaining for Nissl material. The second protocol combines collagen IV immunohistochemistry with aldehyde fuchsine/Darrow red or with erythrosin-phosphotungstic acid-aniline blue staining for detailed study of the capillary network. In the first protocol, microinfarcts are recognizable as radially- oriented funnel-like accumulations of aldehyde fuchsine-positive macrophages. The second protocol recognizes microinfarcts and alterations of the capillary network, at whose center accumulations of dead neurons and aldehyde fuchsine-positive macrophages cluster. In addition, the second protocol permits visualization of abnormalities within the capillary network associated with more recent microinfarcts. Both protocols can be useful for comparing MRI datasets with cortical microinfarcts in corresponding whole brain sections of 100-300 μm thickness.