Presentation
Right sensorineural hearing loss, tinnitus and perioral numbness.
Patient Data
Right cerebellopontine angle mass is seen to extend into the right internal auditory canal (IAC) which enlarges the porus acusticus. The mass extends the whole length of right IAC. This has formed the typical characteristic imaging sign of ice cream cone sign and trumpeted IAC. It demonstrates isointensity on T1WI (to grey matter) and slight hyperintensity on T2WI. Multiple high signal intensity T2W cystic components seen within the mass. On post-contrast, it demonstrates heterogeneous enhancement. No restricted diffusion on DWI/ADC.
On thin slice high resolution heavily T2 weighted imaging, the normal right 7th and 8th cranial nerves are not seen, suggestive of involvement. Anteromedially, the right 6th nerve is escaped and not abutted by the mass. For the cisternal portion of right trigeminal nerve, this mass displaces and compresses it, where the root entry zone of right trigeminal nerve is worst affected by the mass.
Unable to comment on 4th nerve in the current MRI scan (because trochlear nerve is too small to be resolved with current technology). Right 3rd nerve is not involved and normal.
Medially, the mass compressed onto the pons and right middle cerebellar peduncle. No abnormal edema or gliosis within the brainstem and cerebellum.
Right anterior inferior cerebellar artery (AICA) is encased by the mass. Basilar artery, right superior cerebellar artery and right posterior cerebral artery are patent and not involved.
No other abnormal lesion in the left cerebellopontine angle, left IAC and both trigeminal nerves.
A few subcentimeter non specific high signal intensity foci at both deep white matters.
Case Discussion
MRI imaging features are highly suggestive of right vestibular schwannoma.
The most likely differential diagnosis is meningioma but meningioma is usually more homogeneous in appearance (significant signal heterogeneity with cystic or hemorrhagic areas is more typical of vestibular schwannomas than meningiomas). Meningioma has broad dural base and lack of trumpeted internal acoustic meatus sign. Meningioma also rarely causes widening of porus acusticus or extension into internal acoustic meatus.
For this kind of case, the more important points to be included within the radiological report are the close relationship of the cerebellopontine angle mass to the surrounding structures, especially central cranial nerves, vessels/arteries and brainstem, rather than formulating the most likely differential diagnosis. To assess the cranial nerve, radiologists must resort to the thinner slices of MR sequence of highest resolution (usually heavily T2 weighted image sequence, such as CISS 3D).
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