NEURO IMAGING OF CNS LESIONS IN AIDS

Background: The aim of this study was to review and characterize the pattern of CNS lesions in patients suffering from AIDS and to correlate these patterns with clinical disorders. Method: The MR scan, medical records and laboratory findings of 58 AIDS patients were reviewed retrospectively during April 1994 to November 1997 at the Olive view/UCLA and Shiraz Medical Centers, and the patterns of CNS involvement by secondary pathologic processes were divided into three types: 1- Focal parenchymal lesions with enhancement and mass effect that could be solid or ring shaped. 2- Focal parenchymal lesions without mass effect and enhancement. 3- Leptomeningeal enhancement with or without adjacent cortical involvement. Focal parenchymal enhancing lesions appeared to be caused by toxoplasmosis and primary lymphoma. Multiple ring enhancing lesions were most common with toxoplasmosis. Focal parenchymal lesions without mass effect and enhancement were detected specifically in PML and all were deep within the white matter structure. Leptomeninges with or without adjacent cortical enhancement were seen in CNS infectious diseases such as TB, cryptococcosis/coccidioidomycosis and herpes zoster as well as in secondary CNS lymphoma. Granulomatous meningo-encephalitis mostly presented as basal leptomeningitis while herpes meningo-encephalitis was typically located in the temporal lobe. Secondary lymphoma showed high vertex leptomeningeal involvement. The medical history/clinical presentation/CSF findings/stereotaxic biopsy, therapeutic response and postmortem pathologic results were used to distinguish the different etiologic agents. Results: Of a total of 58 HIV seropositive patients, 12 (20%) appeared to be infected by toxoplasmosis, 7 ( 12%) by TB, 8 (14%) cryptococcosis, 5 (9%) coccidioidomycosis, 2 (3%) herpes zoster and 3(5%) cases were diagnosed as PML (progressive multifocal leuko-encephalopathy) according to high serum titer for papova virus group B. Sixteen cases revealed evidence of CNS lymphoma of whom 9 were diagnosed as primary and 7 as secondary CNS lymphoma. In 5 cases HIV infection itself was suspected to be the etiology of the abnormal MRI finding. Conclusion: In spite of newly developing MR spectroscopy techniques for differentiation of CNS lesions in AIDS, categorization of different MRl patterns of CNS diseases in HIV seropositive patients is still helpful in differentiating various types of common CNS lesions in AIDS.