Neuro_MR_Brain: 45 M, progressive cognitive difficulties for 3 months.

1.  Multifocal T2/FLAIR hyperintense lesions which asymmetrically involve the left greater than right cerebral subcortical white matter with particular involvement of the U-fibers and with evidence of hyperperfusion on ASL sequence. Additional lesions are seen in the left greater than right cerebellum, left greater than right middle cerebellar peduncle, right thalamus, corpus callosum and pons. The lesion involving the left forceps major may be more recent because there is associated diffusion hyperintensity which is not clearly consistent with T2 shine through. Overall appearance is most concerning for progressive multifocal leukoencephalopathy (PML), which can be seen in the setting of immunosuppression such as HIV/AIDS, multiple sclerosis patient on Natalizumab, cancer patient on chemotherapy or transplant patient on immunosuppression. Per report 

patient has no history of the prior, but does have history of drug abuse, thus recommend testing for HIV as potential cause and CSF sampling and testing for JC virus. Additional etiologies for these lesions would include other infectious or inflammatory causes such as HIV encephalitis or acute disseminated encephalomyelitis (ADEM). Repeat exam with contrast would be helpful as this exam was terminated prematurely before these could be obtained.