[Pathology of perivascular spaces in the central nervous system].

The perivascular spaces of the central nervous system are involved in various pathological situations. The aim of this paper is to focus on the histopathological lesions of the perivascular spaces which commonly occur in the infectious (bacterial, viral, parasitic), tumoral (carcinoma, lymphoma, leukemia), demyelinating (multiple sclerosis, allergic encephalomyelitis) and vascular diseases of the brain. According to their apparent function in each of these situations an attempt was made to classify the main physiopathological processes involving the perivascular spaces into 3 distinct groups. The perivascular spaces may be considered as follows: (1) double way route between the parenchyma and the leptomeningeal space (extension to the brain of a meningeal pathological process, drainage of parenchymal wastes); (2) elective location of the inflammatory reaction partly as a result of the presence of connective tissue; (3) site of particular lesions such as dilatation, the pathogenesis of which remains unclear.