Absence of thallium-201 brain uptake in progressive multifocal leukoencephalopathy in AIDS patients

To evaluate the presence of thallium-201 brain uptake determined by thalliu m-201 brain SPECT (Tl-201 SPECT) in patients with progressive multifocal le ukoencephalopathy (PML) and AIDS. Material and methods - Six AIDS patients with stereotactic biopsy diagnosis of PML were prospectively evaluated with Tl-201 SPECT, Magnetic Resonance Imaging (MRI), and proton magnetic resona nce spectroscopy (H-1-MRS). Tl-201 SPECT results were compared with 2 patie nts with AIDS and biopsy proven primary CNS lymphoma. Results - In all pati ents with PML, Tl-201 SPECT studies showed lack of uptake while MRI demonst rated subcortical white matter focal brain lesions and H-1-MRS disclosed me tabolic abnormalities. Intense thallium uptake (uptake ratios of 3.2 and 5. 6) was demonstrated in the 2 patients with primary CNS lymphoma. Conclusion s - The present study shows that PML lesions are not detectable on Tl-201 S PECT while MRI and H-1-MRS demonstrate abnormalities, and intense thallium- 201 uptake may be detected in primary CNS lymphoma. These results suggest t hat Tl-201 SPECT is a method which, combined with other non-invasive techni ques such as MRI and H-1-MRS, may help in the diagnostic approach of PML an d to differentiate PML from other high proliferative brain lesions characte rized by positive thallium uptake.