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Enlarged Perivascular Spaces


KEY FACTS

Terminology

  • Perivascular spaces (PVSs)

    • Also known as Virchow-Robin spaces

  • Pial-lined interstitial fluid-filled structures

    • Accompany penetrating arteries

    • Do not communicate with subarachnoid space

Imaging

  • Clusters of variably sized, well-delineated nonenhancing cysts

  • PVSs occur in all locations, at all ages; easily seen in most patients on 3T imaging

  • Most common site for normal PVSs = basal ganglia (clustered around anterior commissure)

    • Midbrain, thalami

    • Deep white matter (including corpus callosum, subinsular cortex, extreme capsule)

    • Almost never involve cortex (PVSs expand within subcortical white matter)

  • PVSs usually 5 mm or less

    • Occasionally expand, attain large size

    • Most common location for expanded (“giant” or “tumefactive”) PVSs = midbrain

    • May cause mass effect, obstructive hydrocephalus

  • Isodense/isointense with cerebrospinal fluid

Top Differential Diagnoses

  • Lacunar infarcts

  • Cystic neoplasm (e.g., dysembryoplastic neuroepithelial tumor, cystic astrocytoma)

  • Infectious/inflammatory cysts

Clinical Issues

  • Should not be mistaken for serious disease

  • Usually remain stable in size over years

Diagnostic Checklist

  • Prominent, but normal, PVSs are identified in nearly all patients, in virtually every location at 3T imaging

Coronal graphic shows normal perivascular spaces as they accompany penetrating arteries into the basal ganglia
and subcortical white matter
. Normal perivascular spaces cluster around the anterior commissure but occur in all areas.

Axial T2WI 3T MR with thin sections shows multiple small perivascular spaces
clustered around the anterior commissure
in the inferior 1/3 of the basal ganglia. These are normal findings.

Axial T2WI in an 88-year-old woman with mild cognitive decline shows innumerable tiny cerebrospinal fluid-like cysts in both basal ganglia
.

Axial FLAIR in the same patient shows that almost all the basal ganglia cysts
suppress, indicating they are filled with fluid similar to cerebrospinal fluid. The symmetry of the cysts and absence of FLAIR hyperintensity indicate these are enlarged perivascular spaces, sometimes called “état criblé” (cribriform state), and not lacunar infarcts.

TERMINOLOGY

Abbreviations

  • Perivascular spaces (PVSs)

Synonyms

  • Virchow-Robin spaces

Definitions

  • Pial-lined interstitial fluid (ISF) -filled structures that accompany penetrating arteries but do not communicate directly with subarachnoid space

IMAGING

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