CT
Intradiploic expansile osteolytic lesion of the left occipital bone, hypodense with no enhancement, containing foci of calcification with destruction of the skull vault mainly the inner table of the skull. There is an intracranial extension compressing the left cerebellar hemisphere, brainstem and 4th ventricle with tonsillar herniation and mild to moderate dilatation of the 3rd and lateral ventricles.