To what object is the appearance of this mass (with one component in the CPA and the other in Meckle's cave) likened to?
To a dumbbell.
What is the most likely diagnosis? What is the main differential?
Trigeminal schwannoma is most likely. A meningioma could have similar appearances.
What features favour a trigeminal schwannoma over a meningioma?
Dumbbell configuration; high T2 signal; heterogeneous enhancement.
MRI through the brain demonstrates a large cerebellopontine angle mass on the right, with a component extending anteriorly into Meckle's cave. The mass is heterogenous on all sequences, and relatively high signal on T2, with avid contrast enhancement, and areas which are presumably cystic.