Intracranial Blastomycosis Presenting as an Enhancing Cerebellopontine Mass

Isolated Blastomyces dermatitidis infection of the central nervous system is an uncommonly encountered entity. If left untreated it can be fatal; thus accurate diagnosis in a timely manner is critical. A 37-year-old white male presented with a severe headache. An MRI scan revealed a right-sided enhancing cerebellopontine angle mass with extension into the internal acoustic canal and diffuse basilar enhancement. After thorough assessment of the patient, an open surgical biopsy of the lesion was performed for pathological evaluation. The biopsy demonstrated broad-based budding yeasts. The cerebrospinal fluid antigen enzyme immunoassay (EIA) (MVista (R)) for Blastomyces dermatitidis was also positive with a level of 4.28 EIA units.