What are the cerebrospinal fluid (CSF) characteristics of primary amebic meningoencephalitis (PAM)?

Updated: Jul 16, 2019
  • Author: Rodrigo Hasbun, MD, MPH; Chief Editor: Michael Stuart Bronze, MD  more...
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Primary amebic meningoencephalitis (PAM) caused by N fowleri is characterized by a neutrophilic pleocytosis, low glucose levels, elevated protein levels, and red blood cells (RBCs). Mononuclear pleocytosis may be observed in patients with subacute or chronic forms of PAM. Demonstration of the trophozoites, with the characteristic ameboid movement, on wet preparations of the CSF has been used for diagnosis. Alternatively, the ameba may be demonstrated in biopsy specimens.

In the presence of exposure, profound peripheral blood eosinophilia, and characteristic eosinophilic pleocytosis, suspicion of meningitis caused by A cantonensis, G spinigerum, or B procyonis should be entertained. Demonstrating the larvae ante mortem is usually difficult, and diagnosis relies on clinical presentation and a compatible epidemiologic history. Serologic tests may aid in the diagnosis. G spinigerum meningitis may mimic cerebrovascular disease in that it may cause cerebral hemorrhage.

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