A Giant Tumefactive Perivascular Space: A Rare Cause of Obstructive Hydrocephalus and Monoparesis.

Cerebral perivascular spaces (PVSs), otherwise known as Virchow-Robin spaces, are interstitial fluid-filled channels, <2 mm in diameter that form around arterial perforators as they course from the cortex into the brain parenchyma. In contrast, a giant tumefactive PVS is a rare entity comprising of clusters of such channels larger than 15mm resembling a neoplastic process as the name suggests. We report a 55-year-old male who presented with unsteady gait, cognitive decline, and left lower limb weakness for 6 months.