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Perivascular spaces

Perivascular spaces, also known as Virchow–Robin spaces, are pial-lined, fluid-filled compartments that surround small penetrating arteries and arterioles as they enter the brain parenchyma from the subarachnoid space. They form part of the brain’s interstitial fluid drainage and immune surveillance system and are a normal anatomic structure.

Although usually microscopic, perivascular spaces may become prominent or dilated and are frequently encountered on neuroimaging, where correct recognition is essential to avoid misdiagnosis.

Synonyms

  • Virchow–Robin spaces

  • Perivascular spaces

  • Pial periarterial spaces

Location

  • Surround penetrating arteries and arterioles entering the brain

  • Extend from the subarachnoid space into the brain parenchyma

  • Commonly seen in characteristic locations:

    • Basal ganglia (along lenticulostriate arteries)

    • Centrum semiovale (along medullary arteries)

    • Midbrain and pons

    • Thalamus

  • Lie between the vascular adventitia and the glial limiting membrane

Anatomical characteristics

  • Pial-lined spaces: Continuous with subarachnoid space

  • Contain interstitial fluid similar to cerebrospinal fluid (CSF)

  • Do not contain neural tissue

  • Typically follow the course of penetrating vessels

  • Valveless and non-enhancing under normal conditions

Relations

Centrally:

  • Penetrating arteries or arterioles

Peripherally:

  • Glial limitans of the brain parenchyma

Proximally:

  • Subarachnoid space

Distally:

  • Terminate within brain parenchyma

Function

  • Interstitial fluid drainage: Facilitates movement of fluid and solutes from brain parenchyma

  • Glymphatic system contribution: Participates in waste clearance, including amyloid-beta

  • Immune surveillance: Allows immune cell trafficking

  • Pressure buffering: Accommodates vascular pulsations

Clinical significance

  • Normal finding: Common incidental observation, especially with aging

  • Dilated perivascular spaces: Associated with small vessel disease, hypertension, and aging

  • Neurodegenerative disorders: Increased burden seen in Alzheimer disease and Parkinson disease

  • Inflammatory conditions: Prominent in vasculitis and demyelinating disease

  • Infection: May be involved in cryptococcosis (gelatinous pseudocysts)

  • Imaging pitfall: Can mimic lacunar infarcts or cystic lesions if misinterpreted

MRI appearance

T1-weighted images:

  • Normal: Hypointense, similar to CSF

  • Dilated spaces: Well-defined, round or linear hypointense structures

T2-weighted images:

  • Normal: Hyperintense, following CSF signal

FLAIR:

  • Normal: Signal suppressed (dark), similar to CSF

Diffusion-weighted imaging (DWI):

  • Normal: No diffusion restriction

Post-contrast T1-weighted images:

  • Normal: No enhancement

CT appearance

Non-contrast CT:

  • Normal: Usually inapparent or small hypodense foci

Post-contrast CT:

  • Normal: No enhancement

MRI images

MRI Perivascular spaces (Virchow–Robin spaces) axial anatomy image -img-00000-00000

MRI images

MRI Perivascular spaces (Virchow–Robin spaces) sagittal anatomy image -img-00000-00000