A heavily calcified mass lesion arises from the inferior aspect of the fourth ventricle and bulges inferiorly to the craniocervical junction. It protrudes through the foramen of Luschka on the right. There is mass effect and slight oedema with in the posterior aspect of the lower medulla. The upper cervical cord is pushed towards the left. The lesion demonstrates contrast enhancement. It lies adjacent to and effaces the medial wall of the intradural right vertebral artery. The findings do not suggest that the lesion is a calcified aneurysm of the vertebral artery. No other mass lesions are identified. No hydrocephalus. Minor degenerative changes are noted within the cervical spine.
Conclusion: Heavily calcified mass lesion arising from the inferior aspect of the fourth ventricle and causing mild mass effect upon the posterior aspect of the medulla and upper cervical cord. The most likely diagnosis is ependymoma. Meningioma, calcified subependymoma is thought unlikely.