= ENLARGED / ATYPICAL VIRCHOW-ROBIN SPACES

= small invaginations of subarachnoid space following pia mater along perforating nutrient end vessels into brain substance

Location: inferior basal ganglia (lenticulostriate arteries); inferior third of putamen = état criblé (cribriform / sievelike); midbrain + deep white matter (perforating medullary arteries); subinsular cortex; thalamus, dentate nucleus; corpus callosum; cingulate gyrus; usually bilateral

• no restricted diffusion
• no enhancement
• normal signal intensity of surrounding parenchyma
• occasionally central high SI on T1WI ← inflow effect
• small 1–2-mm round lesions isointense to CSF
• moderate 2-5 mm round lesions isointense to CSF
• clusters of variably sized bizarre cystic spaces bordering ventricles / subarachnoid space

Cx: hydrocephalus

DDx: multiple lacunar infarcts (adjacent parenchymal hyperintensity), cystic neoplasm (SI not like CSF), infectious / parasitic cysts (enhancing cyst wall); neuroepithelial cyst; mucopolysaccharidosis