<prompt> The perivascular space Virchow-Robin space in the brain is formed between the wall of small penetrating vessels and which structure?Dura materArachnoid membranePia materChoroid plexus  <response>: The perivascular space Virchow- Robin space is formed between the outer wall of small vessels penetrating into the brain and the pia mater, which lines the outer surface of the brain and is only loosely attached to the brain. It is an extension of the subarachnoid space which separates penetrating vessels from brain tissue. 