Peri vascular spaces (PVS), also known as Virchow-Robin spaces, are pial lined intersitital fluid filled spaces that surround perforating vessels 1. They do not have a direct connection with the subarachnoid space and in fact the fluid within them is slightly different.
Overall PVS's are very common, and increasingly seen with better MRI image quality. Depending on your definition, they are seen in 50-100% of patients 2-3 and their relevance is mainly in not mistaking them for pathology.
They are typically less than 5 mm in diameter, but can reach much larger sizes, so called giant peri vascular space or tumefactive perivascular space, and can exert enough mass effect to be symptomatic. When very numerous the brain can have a colander-like appearance referred to as etat crible (as opposed to numerous lacunes = etat lacunaire)
Most commonly they are located in the lower half of the basal ganglia especially along the line of the anterior commissure 3. They are also found in 1:
- substantia nigra
- dentate nucleus
- subinsular region - "subinsular bright spots"
- corpus callosum and cingulate gyrus
The cortical regions are spared
As they are filled with fluid similar to CSF they have appearances akin to water on all imaging modalities and sequences.
- well circumscribed fluid density spaces
- no enhancement
- no calcification
- CT angiography occasionally demonstrates a traversing vessel.
They follow CSF signal on all pulse sequences
When small the adjacent white matter is normal, thus helping to distinguish PVS from lacunar infarcts which have surrounding gliosis. In a minority of cases, especially when they are large thin increased T2 halo may be seen. Usually will have positive mass effect. On T2 sequences a traversing vessel is sometimes seen.
Rarely they can cause obstructive hydrocephalus.
For small "run of the mill" PVSs consider
- choroid fissure cyst
- rim of gliosis seen best on FLAIR
- neutral or negative mass effect
- cyst with a dot sign
- CNS cryptococcosis : if multiple
For giant PVS's consider
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- 1. Salzman KL, Osborn AG, House P et-al. Giant tumefactive perivascular spaces. AJNR Am J Neuroradiol. 2005;26 (2): 298-305. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 2. Song CJ, Kim JH, Kier EL et-al. MR imaging and histologic features of subinsular bright spots on T2-weighted MR images: Virchow-Robin spaces of the extreme capsule and insular cortex. Radiology. 2000;214 (3): 671-7. Radiology (full text) - Pubmed citation
- 3. Jungreis CA, Kanal E, Hirsch WL et-al. Normal perivascular spaces mimicking lacunar infarction: MR imaging. Radiology. 1988;169 (1): 101-4. Radiology (abstract) - Pubmed citation
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Virchow Robin spaces||✓|
|Peri vascular spaces||✗|
|Virchow Robin spaces (VRS)||✗|