Neurocysticercosis and acquired cerebral toxoplasmosis in children.

Neurocysticercosis, prevalent wherever pigs are raised in the presence of poor sanitation, is the most common identifiable cause of new-onset epilepsy throughout the developing world. As immigration patterns have changed, children with neurocysticercosis are seen throughout the United States. Acute cysticercosis, the most common manifestation in children, reflects the host response to the dying parasite. Children typically present with seizures and have an excellent prognosis. Neuroimaging demonstrates a single ring or nodular enhancing lesion surrounded by edema. Short-term anticonvulsant therapy is indicated, but treatment with antiparasitic agents is not required. Other forms, such as active cysts (intact organism), intraventricular or subarachnoid racemous cysticercosis, and cysticercal meningoencephalitis, are less common manifestations of parasitic infection. Toxoplasmosis, caused by the parasite Toxoplasma gondii, can be acquired by ingestion of infected undercooked meat or from oocytes shed in cat feces. Acquired cerebral toxoplasmosis, due to primary or reactivated infections, rarely occurs in immunocompetent children. In children who are immunodeficient as the result of AIDS, chemotherapy, tissue transplantation, or congenital immunodeficiency, toxoplasmosis may be difficult to distinguish from cerebral lymphoma. A variety of techniques, including neuroimaging, Thallium-201 SPECT, polymerase chain reaction analysis of CSF, and special histological methods, may be used to diagnose acquired toxoplasmosis. Antiparasitic therapy, using pyrimethamine and sulfadiazine, and serial neuroimaging often enable clinicians to differentiate toxoplasmosis from other central nervous system lesions. Toxoplasmosis may respond to other antimicrobials, including macrolide antibiotics, dapsone, clinidamycin, and atovaquone. Suppressive treatment is generally required for life in immunodeficient patients. Immunodeficient children with acquired toxoplasmosis have high rates of mortality and neurological sequelae.