Endodermal epithelial cyst in the prepontine cistern extending into the fourth ventricle--case report.

The authors report a case of epithelial cyst, which recurred 32 years after the initial surgical treatment. Computed tomography showed no abnormality, but magnetic resonance (MR) imaging clearly demonstrated a well-demarcated mass in the prepontine cistern, extending into the fourth ventricle. The lesion showed extreme hyperintensity compared with the surrounding brain on both the T1- and T2-weighted images. The ultrastructural features of the cyst suggested an endodermal origin. MR imaging and electron microscopy are essential for correct diagnosis and exact pathogenetic identification of intracranial cystic lesions.