Enlarged perivascular spaces (EPVS) are a common finding on brain imaging that can sound concerning but are often a benign feature of the aging brain. These spaces are small, fluid-filled channels that surround the blood vessels as they penetrate the brain tissue. When these channels become large enough to be seen on a magnetic resonance imaging (MRI) or computed tomography (CT) scan, they are classified as enlarged. EPVS are increasingly recognized as a potential sign of underlying changes in the brain’s small vessels, making them a focus of current neurological research.
The Anatomy of Perivascular Spaces
Perivascular spaces, also known as Virchow-Robin spaces, are extensions of the subarachnoid space that follow the penetrating arteries, arterioles, and venules deep into the brain parenchyma. These spaces are typically microscopic and are not visible on standard imaging in a healthy young person. The fluid within them is similar to cerebrospinal fluid, and they appear as small, distinct oval or linear structures on an MRI.
These channels function as part of the glymphatic system, the brain’s waste clearance pathway. The glymphatic system uses the perivascular spaces as conduits to flush metabolic byproducts and proteins, such as beta-amyloid, out of the brain tissue. This process is important for maintaining overall brain health and is implicated in neurodegenerative diseases. The spaces are also involved in the transport of various substances and immune surveillance within the central nervous system.
Common Factors Associated with Enlargement
The primary factor driving the enlargement of perivascular spaces is the natural process of aging, also known as senescence. The prevalence and severity of EPVS are observed to increase with age in the general population. This age-related increase parallels the rise in vascular risk factors over a lifespan.
Chronic vascular health factors are strongly associated with the physical expansion of these spaces. Hypertension, or high blood pressure, is considered the most prominent risk factor, particularly for EPVS located in the basal ganglia. Sustained high blood pressure can lead to arterial stiffening and higher pulse waves, which damage the walls of the small perforating arteries. This chronic vascular stress is hypothesized to impair the vessels’ ability to effectively pump fluid and clear waste, causing the spaces to dilate.
Other conditions that affect the small blood vessels, such as diabetes and hyperlipidemia (high cholesterol), are also implicated. These conditions contribute to cerebral small vessel disease, a broader pathology for which EPVS are considered a marker. Chronic smoking and poor sleep efficiency have also been independently linked to a higher burden of EPVS.
Clinical Significance and Interpretation
For most people, a small number of scattered EPVS are an incidental finding on an MRI and are considered benign, causing no symptoms. They are classified as enlarged when their diameter exceeds 2 millimeters, though they can sometimes reach up to 10 to 20 millimeters. Clinical significance depends on the number and location of the spaces, leading clinicians to use grading concepts to assess the burden.
A low number of EPVS (Grade 1) is frequently seen in healthy individuals and does not suggest a pathological condition. However, a high burden, such as finding more than 20 spaces on a single slice (Grade 2 or 3), or an appearance described as état criblé (sieve-like state), is concerning. These numerous findings serve as an imaging marker for underlying cerebral small vessel disease.
When EPVS are numerous, especially in the basal ganglia or deep white matter, they are associated with a greater risk of adverse neurological outcomes. A high burden of EPVS is linked to an increased risk of stroke, particularly lacunar ischemic stroke, cognitive decline, and vascular dementia. The location also matters: basal ganglia EPVS are often linked to hypertensive damage. Those in the centrum semiovale (white matter) may be related to cerebral amyloid angiopathy, a condition involving protein aggregation in vessel walls. In rare instances, exceptionally large EPVS can cause symptoms like headache, vertigo, or gait issues due to mass effect on surrounding brain tissue.
Management and Monitoring Strategies
Since enlarged perivascular spaces are a structural finding and not a disease, management focuses on addressing the underlying vascular conditions that may have caused them to enlarge. The most impactful step for patients is the strict control of blood pressure. Managing hypertension through medication and lifestyle changes is necessary for reducing the risk of further small vessel damage.
Controlling other vascular risk factors, such as maintaining healthy cholesterol levels and managing blood sugar in individuals with diabetes, is also a core part of the strategy. Lifestyle modifications, including regular physical activity, a balanced diet, and cessation of smoking, contribute significantly to vascular health and may help stabilize or slow the progression of EPVS.
For patients with a high burden of EPVS, clinicians may recommend follow-up brain imaging, typically an MRI, to monitor for any progression in the number or size of the spaces. This monitoring helps to assess the effectiveness of the vascular risk factor management over time. A waiting strategy is often employed for asymptomatic patients, but for those with symptoms or extremely large spaces, a specialized neurological assessment is warranted.