[Cholesteatoma of the posterior cerebral fossa. 7 cases and review of the literature].

Fifty percent of intracranial epidermoid cysts are located in the cerebral posterior fossa. Clinical presenting features are not specific and vary according to cyst topography and mass effect on neighbouring structures. In CT, the lesion is hypodense as related to the cerebral tissue, but with no specificity. In MRI, the typical form shows quasi-pathognomonic morphologic characters with polyedric contours, a marble aspect, a reduced mass effect as compared to the tumor volume and an evolution signal close to that of cerebrospinal fluid, with no increase after contrast agent injection. Some primary cholesteatomas have a different radiological aspect. They can be hyperdense in CT and have a spontaneous hyperintense signal in T1-weighted MRI sequence. They correspond to complicated epidermoid cysts associated with hemorrhages and granulomatous meningeal reaction whose constitution is very very close to that of cholesterine granulomas.