A 45 year old woman came with complaints of altered sensorium and intermittent fever since one week. She is HIV positive since ten years on is antiretroviral therapy
On the MRI of the brain, multiple T2 hyperintense lesions of variable size with moderate perilesional edema are seen in both cerebral hemispheres, basal ganglia, thalami and midbrain. These lesions show restricted diffusion.; some show the concentric 'target sign' (alternating zones of hypo/hyper isointense signal)