Echinococcosis is caused by tapeworms of the genus Echinococcus, common parasites of dogs and cats, who are the definitive hosts; humans can be intermediate hosts. The disease is endemic in countries around the Mediterranean: Greece, Turkey, and Lebanon have the highest prevalences.162
The small adult worms live in the definitive hostís gut and discharge eggs into feces. If inadvertently ingested by a human, the eggs hatch in the humanís gut, enabling the organism to penetrate the humanís gut wall and spread hematogenously. Once located in a final tissue site, the organism forms a slowly enlarging cyst, a hydatid.
When in the CNS, cysts usually locate in brain parenchyma. Clinical manifestations are secondary to this mass lesion, raised intracranial pressure, or both. They may include:162
Although rare, CNS echinococcosis should be included in the differential diagnosis of any patient with a CNS mass lesion who has lived in an endemic area. Diagnosis is made by neuroimaging, which usually reveals a single, large spherical cystic lesion. There is usually no ring enhancement or associated edema.173
Reviewed and revised March 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.
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