Anatomy
Virchow-Robin spaces are gaps containing interstitial fluid that span between blood vessels and the brain matter which they penetrate. Like the blood vessels around which they form, Virchow-Robin spaces are found in both the subarachnoid space and the subpial space. VRS surrounding arteries in the cerebral cortex and the basal ganglia are separated from the subpial space by one or two layers of leptomeninges, respectively, as well as the pia mater. By virtue of the leptomeningeal cell layer, VRS belonging to the subarachnoid space are continuous with VRS of the subpial space. The direct communication between VRS of the subarachnoid space and the subpial space is unique to the brain’s arteries, as no leptomeningeal layers surround the brain’s veins. Use of the scanning electron microscope has determined that VRS surrounding blood vessels in the subarachnoid space are not continuous with the subarachnoid space because of the presence of pia mater cells joined by desmosomes.
Virchow-Robin spaces may be enlarged to a diameter of five millimeters in healthy humans and are usually harmless. When enlarged, they can disrupt the function of the brain regions into which they project. Dilation can occur on one or both sides of the brain.
Dilated Virchow-Robin spaces are categorized into three types:
- Type 1 dilated VRS are located on the lenticulostriate arteries projecting into the basal ganglia
- Type 2 dilated VRS are located in the cortex following the path of the medullary arteries
- Type 3 dilated VRS are located in the midbrain
Virchow-Robin spaces are most commonly located in the basal ganglia, thalamus, midbrain, cerebellum, hippocampus, insular cortex, the white matter of the cerebrum, and along the optic tract. The ideal method used to visualize Virchow-Robin spaces is T2-weighted MRI. The MR images of dilated Virchow-Robin spaces must be distinguished from MR images of other neurological maladies that are similar in appearance. These illnesses are specifically:
- cystic neoplasms
- lacunar infarctions
- cystic periventricular leukomalacia
- cryptococcosis
- multiple sclerosis
- mucopolysaccharidoses
- neurocysticercosis
- arachnoid cysts
- neuroepithelial cysts
Virchow-Robin spaces are distinguished on an MRI by several key features. VRS appear as distinct round or oval entities with a signal intensity visually equivalent to that of cerebrospinal fluid in the subarachnoid space. In addition, a Virchow-Robin space has no mass effect and is located along the blood vessel around which it forms.
Read more about this topic: Virchow-Robin Spaces
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