Preoperative MR examination prior to clival biopsy. There is motion limiting the T2 sequence images. Within this limitation, the lobulated high T2/low T1 signal, nonenhancing lesion which extends from the right lateral aspect of the clivus to involve the Petrus apex at the petro-clival junction is again demonstrated. This has a nonaggressive appearance on CT demonstrating a sclerotic rim and thinning of the bone which separates it from the CP angle posteriorly (difficult to assess for breakthrough given the progressed thinning ) and anteriorly where it is closely opposed to the posterior aspect of the carotid artery. There is no associated flow void and aneurysm is felt to be unlikely. This measures up to 3.2 by 1.2 x 2.2 cm (previously 2.9 x 1.4 by 2.1 cm in similar dimension). There is no associated mass effect on adjacent structures.Intracranially, there is no other visualized mass, fluid collection, hemorrhage or hydrocephalus. The midline is intact. Limited views of the orbits are unremarkable. Paranasal air sinuses, including the sphenoid, are unremarkable.
Demonstration of the nonaggressive appearing intra-osseous lesion at the right petro-clival junction which, given features such as remodeling of bone, absence of matrix and signal characteristics most likely represents a cephalocele. Differential considerations could include cholesteatoma, neurenteric cyst, or possibly cystic fibrous dysplasia.