Cerebral abscess due to foreign bodies

Case contributed by Frank Gaillard

Presentation

Psychiatric patient. Has scalp ulcer. Now left-arm weakness.

Patient Data

Age: 40 years
Gender: Male

Right-sided cerebral edema surrounding gas and fluid-containing cavity within which are two linear low attenuating regions suggestive of foreign bodies. A skull defect is seen overlying the abnormality.

There are two foreign bodies (~5 cm in length each) extending from the midline vertex at the scalp and lying in an encapsulated fluid collection that contains small volume gas and demonstrates central diffusion restriction with a ring-enhancing wall consistent with abscess formation. Several foci of susceptibility within the cavity suggest small volume hemorrhage This is associated with significant right frontoparietal vasogenic edema, right convexity moderate sulcal effacement and distortion/compression of the occipital horn and trigone of the right lateral ventricle. There is mild leftward shift of the midline structures by 3 mm. The basal cisterns are patent and the foramen magnum is capacious.

Conclusion: Right frontoparietal intraparenchymal abscess formation surrounding the two foreign bodies.

Intraoperative findings

Photo

Intraoperatively two long plastic 'straws' were extracted along with a smaller fragment. The thick abscess cavity was also resected. 

Histology

Sections show a fragment of tissue which has organizing fibrous scar tissue with chronic active inflammation.  The inflammatory cell infiltrate consists predominantly of lymphocytes, macrophages and eosinophils with focal neutrophils.  No evidence of granulomas or malignancy seen.  

Final diagnosis:

Organizing fibrous tissue with moderate chronic active inflammation.  No evidence of malignancy.  

Microbiology

  • + Staphylococcus aureus 
  • + Streptococcus agalactiae (Group B) 
  • + mixed anaerobes
  • no fungal elements

Case Discussion

This unfortunate individual was a chronic schizophrenic. Presumably, what began as a scalp scab became deeper and eventually resulted in osteomyelitis through which we was able to insert these foreign bodies. I am not aware of what specific delusions or co-morbidities they had. 

The critical learning point, in this case, is that foreign bodies can be tricky to identify if you are not open to the possibility of their presence. The initial CT, performed elsewhere, was reported as "surgical tracks" and "locules of gas" only, with no mention of foreign bodies as there was no plausible history for this. 

Had these foreign bodies been left in situ they would have acted as a reservoir for repeated infection. 

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