Persistent neutrophilic meningitis. Report of four cases and review of the literature.

Persistent neutrophilic meningitis is a poorly described variant of chronic meningitis characterized by the persistence of neutrophils in the CSF over extended periods of time (greater than 1 wk) in association with ongoing signs of meningeal inflammation and negative CSF cultures for bacteria and other pathogens. Although the incidence of persistent neutrophilic meningitis is difficult to ascertain, a review of available literature on CNS infections suggests that this entity is not rare. Etiologies of this syndrome are both infectious and noninfectious. Among infectious causes, bacteria such as Nocardia and Actinomyces and systemic mycoses such as Aspergillus and the zygomycetes are the predominant pathogens. The pathogenesis of the persistent neutrophilic CSF response is unknown; with some infectious etiologies, there may be a correlation between neutrophil response and the morphology of the invading organism. Mycelial-like pathogens appear to be the primary stimulus for an ongoing neutrophilic inflammatory response. In cases of persistent neutrophilic meningitis, epidemiologic features and clinical setting frequently offer clues to the etiologic agent, especially in the immunocompromised host. Evaluation should include repetitive cultural and serologic studies of the CSF with special emphasis upon special cultural methods, antigen detection and detection of characteristic metabolic byproducts. Biopsy of extraneural sites of disease should be pursued whenever possible to provide data for an inferential diagnosis of CNS disease. CNS biopsies should be selectively performed in those patients undergoing craniotomy for evaluation of mass lesions. Therapy must be individualized. However, in the immunocompromised host, consideration should be given to the empiric use of amphotericin B with or without a sulfonamide in undiagnosed cases that manifest progressive clinical deterioration.