A case of mistaken identity: intracranial foreign body reaction after AVM embolisation mimicking a glioma.

Intracranial foreign body granulomas are exceedingly rare. We present the case of an intracranial foreign body granuloma found in a 72-year-old male 10 years after he underwent a successful catheter embolisation of a cerebral arteriovenous malformation (AVM). The patient presented to our unit after a fall. He had symptoms of confusion, change in mental status and expressive dysphasia. On initial inquiry, the patient had no past medical history of note. Plain brain CT showed a space-occupying lesion in the left frontal lobe with calcifications suggesting an oligodendroglioma. MRI of the brain revealed a heterogeneously enhancing lesion with cystic-solid areas. The patient underwent a craniotomy and excision of the tumour. A pathological examination of the specimen confirmed that it was a foreign body granuloma. Upon further probing into the patient's past medical history, his family recalled prior treatment many years ago at another institution. The old records revealed that the patient had undergone catheter embolisation of a frontal lobe AVM 10 years previously. A MEDLINE literature search (1980-2005) revealed a handful of case reports describing intracranial foreign body granulomas secondary to previous intracranial procedures. Although rare, foreign body granulomas should be included in the differential diagnosis of patients who have undergone prior neurosurgical procedures and then present with a space-occupying lesion on imaging.