Cerebral abscess

Case contributed by A.Prof Frank Gaillard

Presentation

Headache.

Patient Data

Age: 25
Gender: Male
Modality: CT

A peripherally enhancing lesion is present in the left frontal lobe with central non-enhancement and peripheral oedema. 

Modality: MRI

Within the superior left frontal lobe there is a 4.5 x 3.4 x 3.0 cm ( AP, trans, CC ) rim enhancing lesion. The lesion demonstrates central T1 hypointensity and T2 hyperintensity which does not completely restrict on FLAIR. There is marked diffusion restriction within this central T1 hypointense region. On susceptibility imaging there is a complete hypointense rim identified. The region demonstrates reduced rCBV with mild elevated MTT.

Spectroscopy (not shown) demonstrates elevated lactate peaks within the central T1 hypointense region and no choline elevation in the surrounding T2 hyperintense white matter.

Surrounding the lesion, there is T2 hyperintensity in keeping with vasogenic oedema. This extends inferiorly to the left corona radiata with resultant mass-effect within the left cerebral hemisphere. There is effacement of the frontal and superior parietal sulci. No hydrocephalus. No subfalcine herniation.

No other lesion identified.

No evidence of sinusitis or mastoiditis.

Conclusion:

Rim enhancing lesion within the left superior frontal lobe is most in keeping with a pyogenic abscess. The differential of a GBM/metastasis is less likely given marked central diffusion restriction, and findings on MRS.

Case Discussion

The patient went on to have a craniotomy and aspiration of the fluid centre (pus) and partial debridement of the thick capsule which was adherent to the dura. 

Histology

MICROSCOPIC DESCRIPTION: The sections show fragments of necrotic inflammatory debris consistent with the contents of an abscess. This is delimited by acutely inflamed vascular granulation tissue and more peripheral oedematous and gliotic brain parenchyma. Colonies of Gram positive cocci are identified in the necrotic debris. The features are of bacterial abscess. No evidence of tumour is seen.

FINAL DIAGNOSIS: Bacterial abscess; Gram positive cocci identified.

Microbiology

Calcofluor White Stain: No fungal elements detected

GRAM STAIN

  • Leucocytes +++
  • Gram positive cocci +++
  • Gram negative bacilli +

CULTURE: Streptococcus anginosus group (milleri group) +++

SENSITIVITIES

  • Ceftriaxone S
  • Penicillin S
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Case Information

rID: 29451
Case created: 25th May 2014
Last edited: 28th Oct 2015
Inclusion in quiz mode: Included

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