Female, 22 years old, with HIV infection and CT findings concerning for JC virus infection. Numerous scattered foci of subcortical T2 hyperintensity are seen within the bilateral cerebral hemispheres. These lesions are most notable in the parietal lobes, but are present to a lesser degree in the frontal lobes as well, and are distributed fairly symmetrically. The temporal lobes, basal ganglia and posterior fossa are spared.The lesions do not exert significant mass effect and there is no associated restricted diffusion or susceptibility. The lesions appear not to involve the subcortical U fibers. While there may be some mild increased vascularity in the affected parenchyma, the lesions themselves do not enhance.The overall morphology of the brain is unremarkable. No evidence of intracranial hemorrhage or any abnormal extra-axial fluid collection is seen. The ventricular system is within normal limits.
Numerous symmetrically scattered foci of white matter signal abnormality are detected, predominantly in the parietal lobes but also affecting the frontal lobes to a lesser degree. There is no evidence of significant mass effect and the lesions themselves do not enhance although there may be mild increased vascularity in the affected regions.The differential diagnosis for these findings would include encephalitis in general, and HIV encephalitis in particular. Although not excluded, JC virus/PML is considered less likely as PML typically presents with asymmetric involvement of the hemispheres and involvement of the subcortical U fibers. Additional considerations would include PRES, ADEM, vasculitis.