Perivascular spaces
Updates to Article Attributes
Peri vascularPerivascular spaces (PVS), also known as Virchow-Robin (VR) 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.
Epidemiology
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.
Pathology
They are typically less than 5 mm in diameter, but can reach much larger sizes, so called giant peri vascularperivascular space or tumefactive perivascular space, and can exert enough mass effect to be symptomatic. They tend to enlarge with age and with hypertension. When very numerous the brain can have a colander-like appearance referred to as etat crible (as opposed to numerous lacunes = etat lacunaire)
Location
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. In contrast to lacunar infarcts encountered more frequently in the upper half of the putamen, perivascular spaces are seen more often in the lower half.
Types
Perivascular spaces are divided into three main types 4:
- type 1: located in the area supplied by the lenticulostriate arteries entering the basal ganglia.
- type 2: located in the area supplied by the perforating medullary arteries as they enter the cortical gray matter.
- type 3: located in the midbrain.
Associations
They are usually idiopathic, although they are seen in greater frequency in
- mucopolysaccharidoses 1, e.g. Hunter disease, Hurler disease
- some muscular dystrophies
Radiographic features
As they are filled with fluid similar to CSF they have appearances akin to water on all imaging modalities and sequences.
CT
- well circumscribed fluid density spaces
- no enhancement
- no calcification
- CT angiography occasionally demonstrates a traversing vessel.
MRI
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.
Complications
Rarely they can cause obstructive hydrocephalus.
Differential diagnosis
For small "run of the mill" PVSs consider:
- choroid fissure cyst
-
lacunar infarcts
- rim of gliosis seen best on FLAIR
- neutral or negative mass effect
-
neurocysticercosis
- cyst with a dot sign
- enhancement
- calcification
- CNS cryptococcosis: if multiple
For giant PVS's consider:
- cystic neoplasm(s) 1
- ventricular diverticula
- cystic encephalomalacia
- non-neoplastic neuroepithelial cyst(s)
-<p><strong>Peri vascular spaces (PVS)</strong>, also known as <strong>Virchow-Robin (VR) spaces</strong>, are pial lined intersitital fluid filled spaces that surround perforating vessels <sup>1</sup>. They do not have a direct connection with the subarachnoid space and in fact the fluid within them is slightly different.</p><h4>Epidemiology</h4><p>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 <sup>2-3</sup> and their relevance is mainly in not mistaking them for pathology.</p><h4>Pathology</h4><p>They are typically less than 5 mm in diameter, but can reach much larger sizes, so called <a href="/articles/giant-peri-vascular-space">giant peri vascular space </a>or <a href="/articles/tumefactive-perivascular-spaces-1">tumefactive perivascular space</a>, and can exert enough mass effect to be symptomatic. They tend to enlarge with age and with hypertension. When very numerous the brain can have a colander-like appearance referred to as <a href="/articles/etat-crible">etat crible</a> (as opposed to numerous lacunes = <a href="/articles/etat-lacunaire">etat lacunaire</a>)</p><h5>Location</h5><p>Most commonly they are located in the lower half of the <a href="/articles/basal-ganglia">basal ganglia</a> especially along the line of the anterior commissure <sup>3</sup>. They are also found in <sup>1</sup>:</p><ul>- +<p><strong>Perivascular spaces (PVS)</strong>, also known as <strong>Virchow-Robin (VR) spaces</strong>, are pial lined intersitital fluid filled spaces that surround perforating vessels <sup>1</sup>. They do not have a direct connection with the subarachnoid space and in fact the fluid within them is slightly different.</p><h4>Epidemiology</h4><p>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 <sup>2-3</sup> and their relevance is mainly in not mistaking them for pathology.</p><h4>Pathology</h4><p>They are typically less than 5 mm in diameter, but can reach much larger sizes, so called <a href="/articles/giant-peri-vascular-space">giant perivascular space </a>or <a href="/articles/tumefactive-perivascular-spaces-1">tumefactive perivascular space</a>, and can exert enough mass effect to be symptomatic. They tend to enlarge with age and with hypertension. When very numerous the brain can have a colander-like appearance referred to as <a href="/articles/etat-crible">etat crible</a> (as opposed to numerous lacunes = <a href="/articles/etat-lacunaire">etat lacunaire</a>)</p><h5>Location</h5><p>Most commonly they are located in the lower half of the <a href="/articles/basal-ganglia">basal ganglia</a> especially along the line of the anterior commissure <sup>3</sup>. They are also found in <sup>1</sup>:</p><ul>
-</ul><h5>MRI</h5><p>They follow CSF signal on <strong>all </strong>pulse sequences.</p><p>When small the adjacent white matter is normal, thus helping to distinguish PVS from lacunar infarcts which have surrounding <a href="/articles/gliosis">gliosis</a>. 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.</p><h4>Complications</h4><p>Rarely they can cause <a href="/articles/obstructive-hydrocephalus">obstructive hydrocephalus</a>.</p><h4>Differential diagnosis</h4><p>For small "run of the mill" PVSs consider:</p><ul>- +</ul><h5>MRI</h5><p>They follow CSF signal on all pulse sequences.</p><p>When small the adjacent white matter is normal, thus helping to distinguish PVS from lacunar infarcts which have surrounding <a href="/articles/gliosis">gliosis</a>. 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.</p><h4>Complications</h4><p>Rarely they can cause <a href="/articles/obstructive-hydrocephalus">obstructive hydrocephalus</a>.</p><h4>Differential diagnosis</h4><p>For small "run of the mill" PVSs consider:</p><ul>
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