Acoustic schwannoma - eroding petrous apex

Case contributed by Dr Bruno Di Muzio


Sensorineural hearing loss.

Patient Data

Age: 30 years
Gender: Male

Large enhancing spherical mass at the right cerebellopontine angle, eroding the apex of the petrous bone, almost reaching the labyrinth.

The tumor significantly indents the right pons and cerebellar hemisphere and mildly deviates the fourth ventricle to the left.

No hydrocephalus.

The right middle ear cavity and mastoid air cells are clear.

A lipoma layers over the corpus callosum, which appears normal in size

Small mucous retention cysts in in the maxillary sinuses.

MRI Brain (CPA protocol)


A large mass is seen centered in the right cerebellopontine angle.

Laterally the mass extends into the porous acousticus/IAC which is remodeled.

Inferiorly, there is moderate expansion of the jugular foramen.

The hypoglossal canal appears intact.

Superiorly the mass appears to extend through the tentorial hiatus.

Moderate mass effect on the pons and right middle cerebellar peduncle.

Post administration of contrast there is largely homogeneous enhancement with minor linear areas of non enhancement.


Large right cerebellopontine angle mass lesion.

Given the where the lesion centered, the involvement of the internal acoustic meatus and symptoms, the lesion most likely represents an acoustic schwannoma.

However, expansion of the jugular foramen is noted, raising the possibility that the lesion represents a schwannoma of the 9-11th cranial nerves.

CT Brain (post-operative)


Interval right partial mastoidectomy and temporal craniectomy noted with mild pneumocephalus, and small right cerebellopontine/para-pontine fluid collection with moderate mass effect displacing the right middle cerebellar peduncle and partially effacing the 4th ventricle. Subtle midline linear density superior to this may represent tiny extraaxial blood layering over the posterior falx cerebri.

No any other evidence of a surgical site hemorrhage.

Within the constraints of this study, there is evidence of hypo/mesotympanic posterior wall destruction and partial semicircular and cochlear resection.

Conclusion: No significant early post-op complication identified

MICROSCOPIC DESCRIPTION: The sections show a moderately cellular schwannoma with adjacent bone. It mainly contains Antoni A areas with fascicles of spindle cells. Occasional Verocay bodies are noted. The tumor cells show no significant nuclear pleomorphism. Mitoses are inconspicuous. There is no evidence of necrosis. Sheets of foamy macrophages and some lymphocytes are seen in the background. No evidence of malignancy is identified.

DIAGNOSIS: Right acoustic nerve lesion: Schwannoma.

Case Discussion

This case demonstrates a large right acoustic schwannoma eroding the apex of the petrous bone and exerting mass effect over the posterior fossa structures. It was treated using a retrosigmoid (transmeatal or suboccipital) surgical approach. 

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