The perivascular space (VRS), also referred to as the perivascular lymphatic space, is a normal anatomical structure within the nervous system.MRI is able to show this anatomical and histological structure in vivo and has found a close relationship between increased and enlarged VRS and a variety of neurological disorders.Increased and enlarged VRS is seen in aged brain, hypertension, diabetes, dementia, cerebral white matter lesions, hydrocephalus, multiple sclerosis, central nervous cryptococcal infections, and developmental brain diseases in children. In the past, it has been thought that the VRS is an extension of the subarachnoid space accompanied by a penetrating vessel into the brain parenchyma, which is connected to the subarachnoid space. Currently, it is believed that the VRS is a continuation of the submural space, which is the continuation of the soft meninges with the penetrating arteries and outflow veins into and out of the brain parenchyma. The VRS is divided into three types: ① with the doublestriatal artery entering the basal ganglia area through the anterior penetrating stroma, here called the basal ganglia type; ② with the medullary artery entering the gray matter of the cerebral hemisphere and extending to the white matter, called the cerebral hemisphere type. (iii) With the penetrating artery from the posterior cerebral artery into the midbrain of the VRS, called the midbrain type. The cerebral hemispheric type of VRS is clearly age-related and is a feature of brain aging; no age-related association has been found for the basal ganglia type of VRS. The VRS is often small, about 1-2 mm in diameter, and the penetrating artery within the VRS is <0.4 mm in diameter with a very narrow gap around the vessel, about 0.3 mm, and is therefore not visible on MRI. Only when the VRS is enlarged to a certain extent (diameter >0.66 mm) can MRI reveal it. The VRS with a diameter of <2 mm is generally considered to be a normal anatomical structure and is seen in healthy individuals of all ages; VRS is commonly found in the basal ganglia region and relatively rarely in the hemianopia. VRS >2 mm in diameter is considered to be an enlarged VRS. The enlarged VRS is characterized by smooth and clear borders, is round or linear, is consistent with the lineage of the penetrating artery, and is identical to the cerebrospinal fluid signal on MRI T1WI, T2WI, and FLAIR sequences. There is no contrast enhancement effect and no occupancy effect. FLAIR is useful to distinguish between VRS and ischemic foci, which appear as areas of high signal, and VRS, which have the same signal as CSF and show low signal changes. Large VRS is often first seen around the penetrating artery in the anterior penetrating mass and can be seen in MRI cross-sections around the anterior commissure, even in young adults. Another typical site is the center of the hemianopia.