Intracranial blastomycoma.

Although meningitis is the most common form of central nervous system (CNS) blastomycosis, solitary mass lesions are not an infrequent presentation. Four of our patients presented with focal neurological deficits as a result of single intracranial mass lesions. Only 1 had clearcut evidence of extraneural blastomycosis. One was a coal miner, another worked with soil samples, and one was an engineer for a wood pulp company. All were previously healthy and 2 had diabetes. Complement fixation and immunodiffusion tests were negative in all 4 patients, and white blood cell counts and erythrocyte sedimentation rates were normal. Wet mount of tissue obtained intraoperatively by aspiration demonstrated the organism in 2 cases, culture from a lung lesion made the diagnosis in 1 case, and stain and culture of ventricular fluid revealed the organisms in the fourth case. Multiple cultures of cerebrospinal fluid from lumbar puncture were negative. All 4 patients survived. Amphotericin B alone was curative in 2 cases; surgical removal alone was curative in 1. All 4 computerized tomographic scans revealed isodense or slightly hyperdense single mass lesions with homogeneous contrast enhancement and surrounding edema, and tumor was the preoperative diagnosis in 2 cases. Such scans should suggest CNS blastomycoma in patients from the endemic area, despite the lack of other systemic manifestations. Diagnosis nevertheless rests on the characteristic histopathologic appearance in tissues and/or culture. Solitary intracranial blastomycomas may be less rare than previously thought; at our institution, we observed 4 cases in 4 years.