MRI - AIDS, primary CNS lymphoma: This 32-year-old woman with advanced AIDS presented with right-sided weakness and a seizure. Examination was significant for a moderate receptive aphasia, left gaze preference, slight right hemiparesis and right-sided neglect. The T1-weighted MR image demonstrates a hypointense lesion in the left parietal region that is surrounded by an area of bright contrast enhancement. There is moderate mass effect on the surrounding structures. The corresponding MR spectroscopy image on the right shows a high choline and high lactate peak within the lesion, suggestive of lymphoma.