神经影像与临床PPT.ppt

imaging and clinical 8; VR spaces surround the walls of arteries, arterioles, veins, and venules as they course from the subarachnoid space through the brain parenchyma . Electron microscopy and tracer studies have given insight into the location of VR spaces and clarified that the subarachnoid space does not communicate directly with the VR spaces . Arteries in the cerebral cortex are coated by a layer of leptomeninges that is subtended from the pia mater; by this anatomic arrangement, the VR spaces of the intracortical arteries are in direct continuity with the VR spaces around arteries in the subarachnoid space . The lack of a similar coating of leptomeningeal cells around veins in the cerebral cortex suggests that VR spaces around veins are in continuity with the subpial space . In contrast to arteries in the cerebral cortex, arteries in the basal ganglia are surrounded by notone but two distinct coats of leptomeninges, separated by a VR space that is continuous with the VR space around arteries in the subarachnoid space. ; The inner layer of leptomeninges closely invests the adventitia of the vessel wall. The outer layer abuts on the glia limitans of the underlying brain and is continuous with the pia mater on the surface of the brain and the anterior perforated substance. Veins in the basal ganglia have no outer layer of leptomeninges (similar to cortical veins), which suggests that their VR spaces are continuous with the subpial space . Interstitial fluid within the brain parenchyma drains from the gray matter of the brain by diffusion through the extracellular spaces and by bulk flow along VR spaces. There is evidence from tracer studies and from pathologic analysis of the human brain that VR spaces carry solutes from the brain and are, in effect, the lymphatic drainage pathways of the brain .; Photomicrograph (original magnification, ×20; hematoxylin-eosin stain) of a coronal section through the anterior perforated substance shows two arteries (strai