Acoustic schwannoma

Case contributed by Dr Bruno Di Muzio


Nausea and vomiting associated with unsteady gait.

Patient Data

Age: 65 years
Gender: Male

CT Brain

Right cerebellopontine angle mass is noted causing mass effect on the adjacent right cerebellum and slight distortion of the fourth ventricle but does not occlude it.

No significant ventricular dilation.

Remainder brain is unremarkable. 

Further investigation with MRI is recommended. 


MRI Brain - Posterior fossa

Extra-axial mass in the right cerebellopontine angle. The lesion has low to intermediate signal on T2 weighted images and intermediate T1 signal. There is homogeneous enhancement post administration of contrast. There is a possibility of peripheral nonenhancing cystic elements around the more solid enhancing lesion. The lesion bulges into the porus acousticus which appears mildly expanded.

On the high resolution FIESTA images the nerves in the internal acoustic meatus can be seen separately to the mass. The superior aspect of the lesion abuts the undersurface of the tentorium with a possible dural tail in this region.

Laterally the lesion abuts the petrous ridge, extending to the region of the jugular foramen.

There is moderate edema in the adjacent cerebellar hemisphere and there is moderate mass effect on the right middle cerebral peduncle. Compressed vessels are seen around the lesion. There is distortion of the fourth ventricle and mild hydrocephalus seen involving the lateral and third ventricles.

Conclusion: Right cerebellopontine angle mass with moderate local mass effect. The differential diagnosis is between meningioma and vestibular schwannoma, with meningioma slightly favored on the imaging appearance but both lesions remain in the differential diagnosis.

The patient presented important headache a few days after the MRI, being referred for a new CT scan.  


CT Brain

The iso-mildly hyperdense (pre-contrast), homogeneously enhancing right cerebellopontine angle mass, favored to be a meningioma, is unchanged in overall size, with perhaps slightly more convex margins. It demonstrates marginally increased surrounding vasogenic edema. There is persisting stable 4th ventricular effacement and mass-effect on the right cerebellar hemisphere and cerebral peduncle and stable leftward cerebellar midline shift.

There is also mildly increased obstructive hydrocephalus involving the 3rd and lateral ventricles since the previous imaging.

A small amount of high density is present within the dependent part of the 4th ventricle, not convincing for blood, similar to the previous CT.

No intracranial hemorrhage or extra-axial collection. No evidence of acute infarction. No other new findings since the MRI.

Case Discussion

This case illustrates a right cerebellopontine angle (CPA) mass in an elderly patient. The two main differential diagnosis remain between meningioma and schwannoma. The tumor was resected by a retrosigmoid approach and confirmed as an acoustic schwannoma.

Most vestibular schwannomas have an intracanalicular component, and often result in widening of the porus acusticus resulting in the trumpeted IAM sign, which is present in up to 90% of cases. In a minority of cases (~20%), such in this one, they are purely extracanalicular, only abutting the porus acousticus 1

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