title: Nocardia brain abscess mimicking high-grade necrotic tumor on perfusion MRI.
abstract: Differentiating a pyogenic cerebral abscess from a cystic brain tumor can be a challenge when using morphological and functional imaging techniques. Several studies on MRI perfusion-weighted imaging (PWI) have demonstrated that enhancing abscess capsules have lower cerebral blood volume ratios (rCBV) than the enhancing rims of necrotic tumors. We report a 67-year-old male with a Nocardia cerebral abscess showing restricted diffusion in the necrotic center, but high values for rCBV in the enhancing capsule on PWI, therefore mimicking a high-grade necrotic tumor. Differential diagnosis between cerebral abscesses and necrotic tumors is greatly improved by the adjunct of diffusion-weighted imaging (DWI) and PWI to the morphological magnetic resonance findings; yet there is still overlap. That an abscess may show increased rCBV along the capsule, therefore mimicking a hypervascular brain tumor on PWI, should be considered when attempting a radiological diagnosis of a ring-enhancing brain lesion.
authors.affiliation: Institute of Radiology, Catholic University School of Medicine, Rome, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Cianfoni
authors.forename: Rosalinda
authors.initials: R
authors.lastname: Calandrelli
authors.forename: Pasquale
authors.initials: P
authors.lastname: De Bonis
authors.forename: Angelo
authors.initials: A
authors.lastname: Pompucci
authors.forename: Libero
authors.initials: L
authors.lastname: Lauriola
authors.forename: Cesare
authors.initials: C
authors.lastname: Colosimo
mesh_terms: D000368:Aged; D001922:Brain Abscess / Q000175:diagnosis*; D001932:Brain Neoplasms / Q000175:diagnosis*; D003937:Diagnosis, Differential; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009336:Necrosis / Q000175:diagnosis / Q000473:pathology; D009615:Nocardia; D009617:Nocardia Infections / Q000175:diagnosis*; D010296:Parietal Lobe / Q000382:microbiology* / Q000473:pathology