 Limited sequences were obtained for surgical localization. There is presumably heterogeneously enhancing mass in the mid to inferior fourth ventricle which is dilated, extending into the upper cervical spinal canal at the upper C1-C2 level. T2-weighted images demonstrate central areas of cystic change especially along its cranial margin. There is associated and mild to moderate dilatation of the lateral and third ventricles due to this obstructive process, although flow void is identified through the cerebral aqueduct. Significant T2 hyperintensity within the periventricular white matter to suggest acute transependymal edema. The mass measures 2.4 cm transverse x 2.9cm AP x 5.5 cm CC, and appears to extend out of the foramen of Magendie. There is significant mass effect upon the brainstem, essentially effacement of the prepontine cistern.Sulci also appear somewhat prominent for patient's stated age. There is no midline shift. No extra-axial fluid collection is identified.Normal flow-voids are demonstrated in the major intracranial vascular structures. The midline structures and craniocervical junction are within normal limits. SPINE
1.Large heterogeneously enhancing mass centered in the fourth ventricle extending along the dorsal upper cervical spinal canal, with localized mass effect on the brainstem. Differential diagnosis includes primary neoplasms such as ependymoma given patient's age, as well as medulloblastoma and pilocytic astrocytoma. Rarely, glioblastoma can also have this appearance.2.Associated obstructive hydrocephalus although without MR evidence of acute transependymal edema.3.No acute cord compression. No gross spinal abnormality on this noncontrasted spine exam.