Dementia With Extensive Giant Perivascular Spaces as a Mimicker of Alzheimer Disease: A Case Report.

Giant perivascular spaces (PVS) are usually incidental magnetic resonance imaging findings, but rarely may present with progressive cognitive decline. We report the case of a 70-year-old woman with a 3-year history of gradually progressive amnestic-predominant dementia associated with impairment in instrumental activities of daily living and multidomain deficits on formal cognitive testing. Magnetic resonance imaging of the brain demonstrated extensive bilateral giant cystic spaces in the subcortical, deep, and periventricular white matter following cerebrospinal fluid signal on all sequences with complete FLAIR suppression, consistent with giant PVS. The evaluation for reversible causes was unrevealing, and the plasma p-tau217/Aβ1-42 ratio was negative, arguing against typical Alzheimer-type amyloid pathology. This case highlights giant PVS as an important radiological mimic of Alzheimer disease and supports the consideration of a severe PVS burden as a potential contributor to progressive late-life cognitive impairment.