FIG 10. Histologic section of NBS shows a totally thrombosed medium-sized venous vessel. Focal fibrinoid necrosis (arrowheads) and moderate amount of lymphocyte and plasma cell infiltration is visible in the vessel wall. At the right side of the vessel, necrotic brain tissue with some newly thrombosed small vessel and mononuclear inflammatory infiltration (mainly lymphocytes and histiocytes) is seen (arrows). On the left, there is severe astrogliosis with some gemistocytic differentiation (H and E, original magnification x100).

FIG 11. Schematic representation of the intraaxial venous system of normal parenchyma. Supratentorially, a medullary vein (1) permits bidirectional flow. In the brain stem, especially at the mesencephalic level, intraaxial veno-venous anastomosis (2) is sparse and venous flow is centrifugal, toward the pial veins (pv). ev indicates ependymal vein.