| Glioblastoma | > 65 years old, primary brain tumor | Irregular, thick-walled enhancement; central necrosis; significant vasogenic edema | Single lesion (usually); cerebral hemispheres; crosses corpus callosum (“butterfly”) | Crosses midline; irregular “serpentine” enhancement; arises de novo in brain parenchyma |
| Toxoplasmosis | HIV/AIDS (CD4 < 100); immunocompromised | Ring-enhancing lesions; target-like appearance | Multiple (< 2 cm); Basal ganglia & gray-white junction | Multiple lesions in the basal ganglia in an AIDS patient; improves with empiric therapy |
| Primary CNS Lymphoma | HIV/AIDS (CD4 < 50); immunocompromised; EBV association | Homogeneous, intense enhancement; periventricular | Single (usually); Periventricular; may touch ependymal surface | Single, periventricular, solid enhancement (less often ring-enhancing); EBV+ in CSF |
| Metastasis | Known primary cancer (lung, breast, melanoma, renal) | Well-circumscribed lesions with significant edema | Multiple (usually); Gray-white matter junction | History of primary cancer; lesions are typically spherical and located at the gray-white junction |
| Pyogenic Abscess | Bacteremia, sinusitis, otitis, dental infection | Smooth, thin-walled ring enhancement; central restricted diffusion (DWI) | Can be single or multiple | Bright signal on DWI is highly specific for abscess (water is restricted); often has a smooth, thin capsule |
| Neurocysticercosis | History of travel/living in endemic area (e.g., Latin America) | Cysts in various stages: non-enhancing → ring-enhancing → calcified lesions (“brain stones”) | Multiple, in different stages | History of exposure + presence of calcified lesions and/or scolex (“dot-in-a-box”) |
| Aspergillus | Severely immunocompromised (neutropenia, transplant) | Angioinvasion leading to hemorrhage/infarct; T2-hypointense rim | Often multiple | Angioinvasive nature (hemorrhage/infarct); associated with severe immunosuppression |
| Nocardiosis | Immunocompromised (chronic steroids, transplant); pulmonary nocardiosis | Ring-enhancing lesions, may be multiloculated or “bilobed” | Multiple | Concomitant pulmonary infection; diagnosis via culture (gram-positive, branching filaments) |
| Multiple Sclerosis | Young female (20-40 years); relapsing-remitting neuro deficits | ”Tumefactive” MS can mimic tumor; incomplete “open-ring” enhancement | Multiple, disseminated in time & space | ”Open-ring” enhancement (points away from ventricle); other classic MS lesions (Dawson’s fingers) |