MAGNETIC-RESONANCE-IMAGING, TL-201 SPET SCANNING, AND LABORATORY ANALYSES FOR DISCRIMINATION OF CEREBRAL LYMPHOMA AND TOXOPLASMOSIS IN AIDS

Objectives: To compare the results of magnetic resonance imaging (MRI) and thallium-201 (Tl-201) SPET scanning with laboratory analyses incl uding CSF DNA detection, brain biopsy, and necropsy in the discriminat ion of cerebral lymphoma and toxoplasmosis in patients with AIDS. Meth ods: A retrospective study of 32 patients infected with HIV who had fo cal CNS lesions on MRI, as a result of either lymphoma or toxoplasmosi s. Results: 18 patients had lymphoma, 12 had toxoplasmosis, and two ha d both. Toxoplasma IgG antibodies were detected in only seven patients -four with toxoplasmosis, two with lymphoma, and one with both diagnos es. Epstein-Barr virus DNA was detected in CSF of all six patients wit h lymphoma and none of two with toxoplasmosis. MRI showed multiple les ions in 23 patients, appearances did not discriminate between lymphoma and toxoplasmosis; nine patients had single lesions, of these eight h ad lymphoma (p=0.044, two tailed Fisher's exact test) Tl-201 SPET show ed accumulation in 17 with lymphoma and six with toxoplasmosis (p = 0. 034, two tailed Fisher's exact test). Of nine patients with single les ions on MRI and Tl-201 SPET with focal accumulation eight had lymphoma . Tl-201 SPET uptake ratios of greater than or equal to 2.9 were only seen with lymphoma. Conclusion: Knowledge of patients' toxoplasma sero status does not aid discrimination between lymphoma and toxoplasmosis. Single lesions on MRI with focal accumulation of Tl-201 strongly sugg est lymphoma. Multiple lesions on MRI with Tl-201 SPET uptake ratios g reater than or equal to 2.9 also suggest lymphoma; uptake ratios less than 2.1 do not aid discrimination. Detection of Epstein-Barr virus DN A in CSF is highly sensitive and specific for cerebral lymphoma.