Opportunistic infections (AIDS)

Toxoplasmosis - Most common, multiple rim enhancing lesions in basal ganglia, may be hemorrhagic, eccentric nodule, surrounding edema, decreased on DWI

Cryptococcus - multiple gelatinous pseudocysts in basal ganglia, dilated perivascular spaces

Progressive multifocal leukoencephalopathy (PML) - JC virus, asymmeteric subcortical white matter T2 bright without much mass effect, does not have to be multifocal

TB - meningitis or tuberculoma

Viral Encephalitis - CMV (ependimitis), Herpes (temporal lobe, restricted diffusion), HIV (symmetric bilater periventricular white matter, CD4<100)

Cysticercosis - most common parasitic infection of CNS, from uncooked pork, multiple cystic lesions containing scolex (central dot), calcifications from healded lesions

Lymphoma - can be difficult to differentiate from Toxoplasmosis, but Lymphoma is hyperdense on CT (unlike toxo), demonstrates increased uptake on Thallium imaging (unlike toxo), eccentric target favors toxo