Neurosurgical infections in the compromised host.

Granulocytopenia, cellular and humoral mediated immune dysfunction are predisposing factors to the development of CNS infections in immunosuppressed patients. Brain abscess formation in the compromised host is most commonly caused by enteric bacilli, the bacterium N. asteroides, the fungus Aspergillus fumigatus, or the parasite T. gondii. Mucor and the JC virus cause invasive encephalitis in this patient population. CT and MR imaging have greatly aided in the diagnosis of intracranial lesions because of these agents. Stereotactic biopsy-aspiration for diagnosis and to relieve mass effect combined with systemic antimicrobial therapy is the treatment of choice for intracerebral abscess in the compromised host. Organ rejection and chronic immunosuppressive therapy can complicate surgical intervention in these patients. Only with a high index of suspicion, an aggressive approach to diagnosis, and rapid vigorous therapy may we hope to alter the clinical course in this difficult group of patients.