Eosinophilic meningitis.

Eosinophilic meningitis is a rare clinical entity that can be useful in narrowing the differential diagnosis of central nervous system disease. It is defined by the presence of 10 or more eosinophils/microL in the cerebrospinal fluid (CSF) or a CSF eosinophilia of at least 10%. The most common cause is invasion of the central nervous system by helminthic parasites, particularly Angiostrongylus cantonensis, but other infections as well as noninfectious conditions may also be associated. This review describes the etiologies of eosinophilic meningitis, focusing primarily on the helminths that cause CSF eosinophilia.