MRI shows a rounded, well-defined, heterogeneous lesion, iso-intense on T1-weighted sequences, hyperintense on T2-weighted sequences and FLAIR, with foci of magnetic susceptibility artifact, partial restriction to diffusion, and vivid enhancement after the application of gadolinium. The mass demonstrates fairly low ADC values only slightly higher than adjacent brain.
Although centred on the internal auditory canal, the mass only extends into it along the dural margins without substantially widening the porus acousticus. Posteriorly there is also a well-defined dural tail.
The spectroscopy shows very high alanine peak (resonating at 1.48 ppm) with absent NAA.
Conclusion:
Features favour a posterior fossa meningioma, rather than a schwannoma.