Predominantly periventricular necrotizing encephalitis due to toxoplasmosis: two unusual cases and review of literature.

Ventriculitis or periventriculitis as a predominant pattern of tissue involvement in cerebral toxoplasmosis was always a rare event, even at the height of the acquired immunodeficiency syndrome (AIDS) era. Ventriculitis on premortem neuroimaging or at autopsy in AIDS patients chiefly led to differential diagnoses of primary central nervous system lymphoma (PCNSL) or cytomegalovirus ventriculitis, not toxoplasmosis. Usually cerebral toxoplasmosis manifests as multifocal, necrotizing, hemorrhagic foci of cerebritis or abscesses. We report two non-AIDS patients with cerebral toxoplasmosis that presented with predominant ventriculitis/periventriculitis, with diagnosis in both cases made only at postmortem examination. A 90-year-old woman, with autoimmune hemolytic anemia and large granular lymphocytic leukemia diagnosed 2 1/2 years prior, presented with altered mental status. Neuroimaging revealed a necrotic 5.4 x 4.6 x 3.5 cm mass extending across corpus callosum and involving both periventricular frontal horn regions, diagnosed as "butterfly" glioblastoma or possible PCNSL. No consideration of infection was raised, care was withdrawn. A 44-year-old woman with systemic lupus erythematous (SLE) treated with prednisone presented with fever and generalized malaise with rapid progression to agitation and confusion. Infection was suspected, but never confirnied on extensive premortem workup. Brain autopsy in both patients revealed severe necrotizing toxoplasmosis virtually confined to periventricular regions. In the first case, necrosis extended across the corpus callosum. Large numbers of organisms were found microscopically, reflecting their immunocompromised, and untreated, status. Cerebral toxoplasmosis should be included in the differential diagnosis when encountering patients with necrotizing ventriculitis, even in the non-AIDS immunosuppressed population.