MRI of the brain demonstrates a large heterogenous mass centered in the 4th ventricle and herniating out of the left Foramen of Luschka. In post-contrast T1 weighted images it shows vivid but heterogenous enhancement. The 4th ventricle is completely effaced; however, there is no surrounding edema or significant hydrocephalus, The patient was a young adult who presented with ataxia and headaches. He underwent posterior fossa craniotomy and resection of the tumor. Histology revealed classic features of an ependymoma with perivascular pseudorosettes. Case produced with permission, courtesy of Dr. Frank Gaillard. Radiopaedia. Complete case is here.