Eosinophilic meningitis and hydrocephalus in an infant.

Central nervous system invasion by helminths is the most frequent cause of eosinophilic pleocytosis in the CSF. Although CSF eosinophilia is an unusual finding in the continental United States, it is not an uncommon observation in cases of meningitis in Hawaii and the South Pacific. The rat lungworm, Angiostrongylus cantonensis has been implicated as the causal agent responsible for cases of eosinophilic meningitis in these areas. The diagnosis of eosinophilic meningitis secondary to A cantonensis is generally an indirect one, based on the characteristic clinical findings, documented eosinophilic pleocytosis of the CSF, and history of consumption of food likely to contain infected larvae. Hydrocephalus developed in a 9-month-old infant from Samoa with absolute eosinophilia and an eosinophilic pleocytosis of the CSF.