Perivascular spaces (PVS), also known as Virchow-Robin spaces, are fluid-filled channels surrounding small blood vessels as they travel through brain tissue. These spaces are a normal part of brain anatomy. While typically microscopic and not visible on imaging, they can appear larger or “prominent” on brain scans like MRI. A prominent perivascular space does not automatically indicate a serious medical problem; it is often an incidental finding.
The Role of Perivascular Spaces
Perivascular spaces are compartments that encircle brain blood vessels as they penetrate the tissue. These spaces contain interstitial fluid and are extensions of the subpial spaces, which are located between the brain tissue and the pia mater, a delicate membrane covering the brain. The pia mater also lines the perivascular spaces.
A primary function of these spaces is their involvement in the brain’s fluid drainage and waste clearance system, often referred to as the glymphatic system. This system facilitates the movement of cerebrospinal fluid (CSF) into the brain parenchyma, where it exchanges with interstitial fluid and helps remove metabolic waste products, such as amyloid-beta. It functions like a specialized plumbing system for the brain, flushing out cellular debris and harmful substances. This process is particularly active during sleep, contributing to overall brain health.
Factors Leading to Prominence
Perivascular spaces can appear prominent on imaging scans, such as MRI, for several reasons, with age being a common factor. As individuals age, the number and size of these spaces tend to increase, often without associated symptoms. This age-related prominence is a common finding in older populations.
Beyond normal aging, other factors are associated with increased prominence of these spaces. High blood pressure (hypertension) is one such factor, potentially leading to arterial stiffening and changes in vessel walls that contribute to their enlargement. Certain neurological conditions, including cerebral small vessel disease, have also been linked to more widespread or numerous prominent perivascular spaces. While these associations exist, the presence of prominent perivascular spaces alone does not always signify a disease.
Interpreting Prominent Perivascular Spaces
When a brain scan reveals prominent perivascular spaces, it is often a benign finding, particularly in older individuals. Radiologists commonly encounter these on MRI scans, where they appear as small, well-defined, fluid-filled structures that resemble cerebrospinal fluid (CSF) in signal intensity. They can look like small dots if viewed perpendicular to the vessel or linear structures if seen parallel to it.
In many cases, these visible spaces are a normal variation or an expected change with age, and they do not cause symptoms or require medical intervention. Normal PVS are generally less than 2 mm in diameter. Radiologists describe their location and extent, noting that such findings are often incidental and carry no immediate clinical significance.
Situations Requiring Medical Attention
While prominent perivascular spaces are often benign, situations exist where they warrant further medical evaluation. If the prominence is unusually widespread, exceptionally large, or atypical for a person’s age, a doctor might investigate further. Giant perivascular spaces, though rare, can sometimes cause symptoms if they exert pressure on surrounding brain tissue.
New or unexplained neurological symptoms appearing alongside prominent perivascular spaces should always prompt a medical consultation. These symptoms could include persistent severe headaches, cognitive changes like memory or thinking problems, focal weakness, or seizures. A healthcare provider will consider the imaging findings within the context of a patient’s overall health history and symptoms to determine if any further tests or treatments are necessary.