Figure 12d. Medulloblastoma in a 10-month-old boy with nausea and vomiting for several months and recent onset of lethargy and failure to meet developmental milestones. (a) Axial CT image shows a heterogeneous mass involving the cerebellar vermis and hemisphere with extension toward the left cerebellopontine angle. The soft-tissue portion near midline is hyperattenuated, whereas the fluidlike compartment is more lateral and posterior in location. (b) Axial T1-weighted MR image reveals mild hypointensity of the soft-tissue portion with moderate hypointensity in the cystlike region. This latter signal intensity is more hyperintense relative to normal CSF, thereby indicating that it is not simple fluid but likely contains proteinaceous debris or possibly hemorrhage. The extension through the left foramen of Luschka (arrow) is better seen. (c) Axial T2-weighted MR image demonstrates heterogeneity within the soft-tissue portion. (d) Contrast-enhanced axial T1-weighted MR image shows peripheral rim enhancement of the cystlike portion and more solid enhancement within portions of the soft-tissue section. At surgery, the mass was seen to extend through the left foramen of Luschka.