Fact-sheet: Dilated Wirchow - Robin spaces
Updated on 09/17/2021 at 12:16 PM
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Definition
The Virchow-Robin perivascular space (PVS) corresponds to an extension of
the subarachnoid space that surrounds and accompanies vessels as they
pass through the cerebral parenchyma.
These spaces form a sort of sheath filled with cerebrospinal fluid (CSF), bounded on one side by the vessel wall and on the other by the pia intima (
avascular layer of the pia mater).
Giant cystic dilatation of PVS is rare, seldom reported in the literature, and its etiology remains unclear.
The pia mater, the innermost layer of the meninges, adheres completely to the
surface of the brain. It comprises two layers:
• an inner, avascular layer, made up of elastic and
reticular fibers. It accompanies arteries as they penetrate the
cerebral parenchyma. Between it and the vessels, a perivascular space,
or Virchow-Robin space, persists
• an outer layer, formed of collagen fibers, joined to the arachnoid
by arachnoid trabeculae. Vessels course through this
layer.
The most frequently cited etiologies are:
- advanced age (cerebral atrophy),
- arterial hypertension (through spiral elongation of small intracerebral arterioles under the effect of hypertensive
surges),
- dementia,
- disorders of arterial wall permeability, responsible for "trapping" of interstitial fluid.
Classification:
- Type I: Along the internal and
external lenticulostriate arteries in the anterior perforated substance.
- Type II: Accompanying perforating medullary arteries
of the convexity and extending toward the white matter.
- Type III: At the midline, especially at the level of the
midbrain
CT
Dilated PVS are visible on CT as small, round and/or tubular cystic formations without mass effect.
Dilated PVS are hypodense relative to the surrounding parenchyma, with density identical to that of CSF.
On contrast-enhanced series, a vessel can sometimes be seen at the center of the PVS.
The surrounding parenchyma is of normal density.
MRI
Round, ovoid, or curvilinear lesion, well defined, with smooth margins:
- signal identical to cerebrospinal fluid on all sequences
- location consistent with penetrating vessels
- typically without mass effect
Classification
Classification:
- Type I: Along the internal and
external lenticulostriate arteries in the anterior perforated substance.
- Type II: Accompanying perforating medullary arteries
of the convexity and extending toward the white matter.
- Type III: At the midline, especially at the level of the
midbrain
Differential diagnosis
The main differential diagnoses to consider are:
- lacunar infarcts
- other cystic lesions: arachnoid cysts, ependymal cysts, neuroepithelial cysts
- Cryptococcosis
- Neurocysticercosis
- ventricular diverticula
- mucopolysaccharidoses
