Figure 10a. Medulloblastoma in a 6-year-old boy with recurrent headaches. (a) Axial T1-weighted MR image shows a heterogeneous soft-tissue mass (arrows) in the right cerebellar hemisphere with an associated peripheral cystlike region. The soft-tissue portion is hypointense relative to the normal cerebellum. Several focal areas of fluidlike hypointensity are noted within the mass. (b) Axial T2-weighted MR image shows that the soft-tissue component is slightly hyperintense relative to the normal cerebellum. The fluidlike areas are again noted. (c) Contrast-enhanced axial T1-weighted MR image demonstrates intense but heterogeneous enhancement of the soft-tissue portion. The nonenhancing regions represent either cystic degeneration or necrosis.