Rare Case of Hydatid Cyst in the Cerebellopontine Cistern.

Posterior fossa localization of a hydatid cyst is uncommon; in these cases, the cysts usually grow in the cerebellum. Localization within the subarachnoid spaces or the cerebrospinal fluid ventricular system is exceptional. In the present report, which appears to be the sixth in the literature, we describe a case of a hydatid cyst in the cerebellopontine cistern. Magnetic resonance imaging findings revealed a nonneoplastic cystic lesion mimicking an arachnoid cyst. The hydatid nature of the cyst was unexpected preoperatively. The cyst was successfully removed using the puncture, aspiration, irrigation, and resection technique via a retrosigmoid approach. Histopathologic examination confirmed the cysts to be Echinococcus granulosus in nature. Hydatid cyst may be considered in the differential diagnosis of arachnoid cysts of the cerebellopontine cistern to determine which surgical procedure to perform and to avoid unexpected complications.