Legend Axial T2 and coronal T1W (IR) images of the posterior fossa show a very large heterogeneous mass in the fourth ventricle. The mass extends through the left foramen of Luschka into the CP angle, causing compression and marked displacement of the brainstem to the right.

Legend Coronal T1W image (upper left) confirms the 4th ventricular mass. Axial, coronal and sagittal post contrast T1 weighted images demonstrate a heterogeneous, enhancing mass in the fourth ventricle. The lateral and third ventricles are markedly enlarged indicating obstructive hydrocephalus. Key words: mri tumor neoplasia

Brain Diagnosis: Primitive Neuro-Ectodermal Tumor (PNET)