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FIG 1. Images in a 60-year-old woman with viral encephalitis. MR images in A–E were obtained at the subacute stage (13 days after symptom onset).
A, Axial T2-weighted image shows asymmetric confluent low intensity in the left frontoparietal lobe.
B, FLAIR image also shows subcortical low intensity with diffuse cortical high intensity in the affected hemisphere.
C, Axial contrast-enhanced T1-weighted image shows mild leptomeningeal enhancement in the left hemisphere.
D, DW image shows mild hypointensity in the subcortical white matter in the left hemisphere.
E, ADC map also shows mild hypointensity of the subcortical low-intensity lesions. Mean ADC value of the subcortical lesions was 0.65. Hypointensity of the subcortical low-intensity lesion on the DW image in spite of low ADC may be explained by the low-intensity T2 shine-through effect.
F, Follow-up FLAIR image obtained 14 days after the initial MR examination shows that the subcortical low intensity is no longer demonstrated but has changed to intermediate to slightly high signal intensity. Localized edema is seen at the biopsy site in the left parietal lobe. Leptomeningeal enhancement was not demonstrated on the follow-up contrast-enhanced T1-weighted image (not shown).
G, Photomicrograph of the surgical specimen obtained 4 days after the initial MR examination shows no structural abnormality in the subcortical white matter except for focal myelin pallor (Luxol fast blue stain, original magnification x40). Inset shows perivascular mononuclear cell infiltration (arrow) in the white matter (immunohistochemical stain, original magnification x200). The cells are reactive for CD3, a marker for T lymphocyte.
H, Photomicrograph from histochemical study of iron stain reveals no evidence of accumulated iron in the cortex and subcortical white matter (Perls stain, original magnification x40).
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