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FIG 8. Images obtained in a 35-year-old man with headache who underwent a biopsy and a third ventriculostomy procedure. Axial T1-weighted MR image (A) shows the giant perivascular space in the left midbrain. A section through the cyst wall (B) shows red-stained collagen in the leptomeninges on the outer aspect of the cyst wall coating the underlying brain tissue that forms the bulk of the cyst wall. No lining of pia matter is present on the inner aspect of the cyst. (Hematoxylin van Gieson stain, original magnification x20) There is extensive gliosis in the cyst wall as demonstrated by the numerous brown stained fibrillary processes within the brain tissue (C). (Immunocytochemistry for GFAP, original magnification x20) A high-power view (D) of the cyst wall near the pia arachnoid outer coating (top of picture). Reactive astrocytes are seen toward the bottom of the illustration. No neurons were identified. (Hematoxylin and eosin stain, original magnification x40)
