I saw the "shrimp sign": Cerebellar progressive multifocal leukoencephalopathy.

The shrimp sign is characterized by a well-defined lesion in the deep cerebellar white matter, with hyperintense signal on T2- and hypointense signal on T1-weighted imaging, abutting and outlining the dentate nucleus, unilaterally or bilaterally. This sign has high sensitivity and specificity for cerebellar progressive multifocal leukoencephalopathy (PML) within the correct clinical scenario. In this article, we present a case of cerebellar PML in a woman living with human immunodeficiency virus, who was not using antiretroviral therapy, and presented the shrimp sign on brain MRI.