Abstract
A 9-month-old boy with recent signs of delayed behavioral development was found to have a large epithelium-lined cyst located ventral to the medulla oblongata. The cyst was resected, and microscopic examination revealed its wall to be lined by a single layer of columnar epithelial cells containing secretory granules, a coating material, and a basement membrane. Electron microscopic findings suggested an endodermal origin. Previous reports of cystic lesions in the posterior fossa, apart from arachnoid cysts, are reviewed and the role of magnetic resonance imaging in locating lesions in the posterior fossa is discussed.
