MRI Shrimp Sign and Parietooccipital Lesion in Progressive Multifocal Leukoencephalopathy.

Recognizing the MRI characteristics of progressive multifocal leukoencephalopathy is essential for early diagnosis. This report describes the oldest known case of an 83-year-old man with rapidly progressive dementia and HIV-associated classic PML. Brain MRI revealed hallmark findings, including asymmetric, continuous, non-enhancing subcortical lesions in the parietooccipital regions and the "shrimp sign" in the cerebellar white matter.