Perivascular Spaces: Neuroimaging, Microanatomy, Homeostasis, and Pathophysiologic Mechanisms of Disease

Perivascular spaces in the brain are microscopic pial-lined structures that surround small blood vessels and form the basis of the glymphatic system, which has a crucial role in fluid homeostasis and clearance of cellular waste byproducts. While often seen on MR imaging, enlarged perivascular spaces have been associated with multiple pathologies, such as neurodegenerative disorders, cerebral amyloid angiopathy, infectious or inflammatory diseases, and congenital conditions such as mucopolysaccharidoses. In addition, neoplasia can involve and spread via perivascular spaces, such as neurocutaneous melanosis. Lastly, congenital giant perivascular spaces are sometimes tumefactive and can be confused with neoplasia, leading to misdiagnosis. The morphologic characteristics, anatomic location, and burden of perivascular spaces may aid in differentiating the underlying etiology. Understanding the role of perivascular spaces in the brain and pathophysiologic mechanisms of disease that result in characteristic manifestations is essential for diagnostic interpretation.

Learning Objective: To describe the normal anatomy and variable appearance of perivascular spaces and their role in the glymphatic system and to understand pathologic manifestations of perivascular spaces in various disease processes associated with glymphatic dysfunction, and their possible underlying mechanisms