Histological and immune-histological examination of brain biopsy. Microscopic examination showed nonspecific meningoencephalitis involving perivasculitis of leptomeninges (arrows) and cortical gray matter (A). The cellular infiltrate was mainly composed of CD-3-positive T-lymphocytes (B) and CD-68-positive macrophages (C) with minimal CD-20-positive B-lymphocytes (D). PAS staining showed no deposits (E). Congo-red staining revealed amyloid positive blood vessels (F); the amyloid was disclosed to be amyloid-β by immunohistochemical staining (G).