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Nocardia brain abscess mimicking high-grade necrotic tumor on perfusion MRI
Alessandro Cianfoni1, Rosalinda Calandrelli, Pasquale De Bonis
1Institute of Radiology, Catholic University School of Medicine, Rome, Italy.
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.
Insights
Differentiating brain abscesses from tumors can be difficult. A Nocardia abscess mimicked a tumor on perfusion-weighted imaging (PWI) with high rCBV, highlighting the need for diffusion-weighted imaging (DWI) in diagnosis.
Area of Science:
- Neuroradiology
- Neuroimaging
- Infectious Diseases
Background:
- Distinguishing pyogenic cerebral abscesses from cystic brain tumors using imaging is challenging.
- Perfusion-weighted imaging (PWI) typically shows lower cerebral blood volume ratios (rCBV) in abscess capsules compared to necrotic tumors.
- Morphological and functional MRI techniques are crucial for differential diagnosis.
Observation:
- A case of Nocardia cerebral abscess presented with restricted diffusion in the necrotic center.
- The abscess capsule showed high rCBV values on PWI, mimicking a high-grade necrotic tumor.
- This finding contrasts with typical PWI characteristics of cerebral abscesses.
Findings:
- Diffusion-weighted imaging (DWI) and PWI, when adjunct to morphological MRI, improve differential diagnosis between abscesses and tumors.
- However, overlap in imaging findings can still occur.
- Cerebral abscesses can exhibit increased rCBV in the capsule, potentially mimicking hypervascular brain tumors on PWI.
Implications:
- Radiologists must consider the possibility of increased rCBV in abscess capsules when diagnosing ring-enhancing brain lesions.
- This case underscores the importance of integrating DWI and PWI findings for accurate radiological diagnosis.
- Awareness of atypical PWI findings in cerebral abscesses is critical for appropriate patient management.
