Susceptibility-weighted imaging in parenchymal neurosyphilis: identification of a new MRI finding.

<bold>Background: </bold>General paresis (GP) is a late form of parenchymal neurosyphilis causing dementia and neuropsychiatric disorders. The diagnosis is often difficult since the clinical signs are protean. So far, neuroimaging has played a minor role as radiological findings are not specific.<bold>Methods: </bold>We studied three immunocompetent patients, admitted to hospital for cognitive impairment. The diagnosis of neurosyphilis was formulated on the basis of serological texts and cerebrospinal fluid analysis. The patients underwent a 3 T MR examination including susceptibility-weighted imaging (SWI) sequence before and after the initiation of penicillin therapy.<bold>Results: </bold>In all patients, SWI revealed cortical hypointensity, mostly distributed in frontal and temporal lobes. In drug-naive patients, the hypointensity extended over the whole cortical thickness, from the cortical/subcortical junction to the pial surface. After starting the penicillin therapy, the cortical hypointensity partially reversed, involving only the deep cortical layers.<bold>Conclusions: </bold>The MRI pattern at SWI observed in patients with GP was not reported in other infectious or inflammatory disease of the central nervous system, thus we suggest it could be a peculiar radiological finding of the disease. On the basis of previous pathological data, we hypothesise that cortical SWI hypointensity could be expression of iron deposits within activated microglia. [ABSTRACT FROM AUTHOR]