Perivascular Space

Perivascular space elegantly demonstrating that the space is indeed around a vessel.
Perivascular spaces, also known as Virchow-Robin spaces, are pia-lined fluid-filled spaces surrounding perforating vessels. They do not have a direct connection to the subarachnoid space, and indeed the fluid within them is slightly different. They typically are less than 5mm in diameter, but can reach much larger sizes, the so-called giant perivascular 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).
Read more on VR spaces and see other examples at Radiopaedia.org here
Credit: Dr Frank Gaillard
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