How to differentiate between medulloblastoma and exophytic brainstem glioma?
Medulloblastoma is usually highly cellular tumor that should display restricted diffusion on DWI, also it is well defined and should be separated from the posterior aspect of brainstem. Moreover it has characteristic taurine peak elevation on MRS.
The mass returns hypointense signal on T1, hyperintense signal on T2 and FLAIR, bright signal on DWI and ADC denoting facilitated diffusion. No significant post contrast enhancement. It is ill defined and no line of cleavage between the mass and the posterior pons. MRS reveals reduced NAA, elevated Cho and in some areas there is elevated lactate as well denoting degeneration.