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FIG 4. A, Postmortem coronal T2-weighted image of the right frontal lobe 22 months after the onset in case 3, showing diffuse hyperintensities in the cerebral white matter. B, Myelin-stained section corresponding to panel A, demonstrating diffuse pallor of the cerebral white matter. C, Histologic specimen of the area of highly increased signal intensity (A and B, squares), revealing a severe loss of myelin and axons, tissue rarefaction, foamy macrophages (arrowhead), and proliferation of gemistocytic astrocytes (arrow). D, Area of moderately increased signal intensity (A and B, circles), showing mild tissue rarefaction. There are also foamy macrophages (arrowhead) and gemistocytic astrocytes (arrow). Because tissue rarefaction and gemistocytic astrocytosis are exceptional features in secondary degeneration, these histologic features indicate primary involvement of the white matter.
