Case #10

CT

• Hyperattenuating posterior fossa mass centered in the fourth ventricle
• Obstructive hydrocephalus with marked enlargement of the lateral and third ventricles and periventricular edema
• Generalized sulcal and cisternal effacement

MRI

• Large, heterogeneously enhancing mass arising at the floor of the fourth ventricle and extending through the right greater than left foramina of Luschka and foramen of Magendie into the prepontine and premedullary cisterns and upper cervical spinal canal
• Extensive corresponding mass effect on the cerebellum, pons, medulla, and upper cervical spinal cord
• T2 signal intensity is similar to that of gray matter
• No corresponding restricted diffusion
• A few foci of internal susceptibility artifact likely represent calcification in correlation with the CT
• Encasement of the basilar and intradural vertebral arteries