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Progressive Multifocal Leukoencephalopathy (PML) is caused by JC virus, occurring almost exclusively in the immunocompromised. For those affected by it, prognosis is grim with survival rate of 40% at 1 year in patients with HIV and PML. No anti-viral therapy exists for PML and as such management relies on reversal of cause of immunosuppression. Diagnostic confirmation is made through JC virus PCR testing on CSF. Imaging in the correct clinical context can be highly suggestive of PML, an example of which we present.

Case Report:

A 61-year-old female with poorly controlled HIV, untreated Hepatitis C, hypertension, and previously treated pulmonary tuberculosis presented for generalized body aches and altered mentation. On admission, she had a CT abdomen pelvis w/contrast, CT thorax for workup. CT head showed contrast enhancement (given during CT AP w/contrast) in the cerebellum, brain stem, bilateral temporo-occipital lobes. Patient subsequently had an MRI brain w/wo  showing T2/FLAIR hyperintensities in subcortical white matter predominantly in posterior cerebral hemispheres, brainstem, cerebellum. These imaging findings were consistent with “Shrimp sign”  and “Barbell sign” which in the right clinical context are each specific for PML. These lesions were associated with ill-defined minimal contrast enhancement. LP showed WBC 1, RBC 0, protein 89.7, Glc 45 (serum 50), JC virus PCR positive.

Discussion:

Shrimp sign consists of T2/FLAIR hyperintensity that involves the middle cerebellar peduncle and medial cerebellum with sparing of the dentate nucleus giving the appearance of a shrimp.

The Barbell sign consists of T2/FLAIR hyperintensity in both parieto-occipital cortices joined by a rim of hyperintensity involving the splenium. This gives the appearance of a barbell.

These two radiographic signs can clue one in towards diagnosis of PML in the correct clinical context.

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