MRI confirms the diagnosis. The mass has a characteristic growth pattern whereby it insinuates itself around structures, (note the relationship to the basilar artery) and scalloped margins. Although it is of near-CSF intensity on T1 and T2 weighted images, it does not fully attenuate on FLAIR or FIESTA, instead having a dirty, heterogeneous appearance. There is no contrast enhancing solid component and it does not extend into the internal acoustic meatus.
The imaging diagnosis is confirmed on diffusion weighted imaging (DWI) and (ADC) which demonstrates restricted diffusion (note that it is very bright on DWI due to a combination of T2 shine-through and restricted diffusion).