Presentation
Tinnitus in the right ear, vertigo, and facial pain.
Patient Data
There is a large well-defined extra-axial complex mass in the right cerebellopontine angle (CPA) cistern, centered in the internal auditory canal (IAC), which is low signal intensity to grey matter on T1-weighted MR image, and heterogeneous hyperintensity on T2 WI.
Axial contrast-enhanced T1 WI reveals the irregular enhancement of the mass. It shows multiple internal non-enhancing cystic changes. DWI revealed no diffusion restriction of the tumor. There is a disproportionately small amount of edema, given the size of the mass. The lesion measures 4.0 x 3.8 x 3.4 cm.
The tumor extends from the medial aspect of the IAC, which is enlarged and continues through the porus acusticus into the cerebellopontine angle cistern. A sizable mixed tissue component is present more medially in the CPA, with irregular necrotic or cystic zones interspersed with more cellular tissue.
This mass exerts a mass effect on the right side of the pons, the ipsilateral middle cerebellar peduncle, and the anteromedial part of the right cerebellar hemisphere. The fourth ventricle is compressed and displaced to the left side, and consequently, there is dilatation of the supratentorial ventricular system. There is a widening of the CPA cistern posterior to the tumor, indicating its extra-axial origin.
Case Discussion
Vestibular schwannomas, also known as acoustic neuroma, are benign neoplasms of the vestibulocochlear nerve sheath and are the most common cerebellopontine angle (CPA) tumor.
Contrast-enhanced CT can serve as an alternative if the patient cannot undergo MR imaging 1. MR imaging is the preferred technique and plays a significant role in tumor characterization, surgical planning, and post-therapeutic evaluation 1,2. Contrast is essential because a non-enhanced study can miss small tumors.
In the present case, MR images show evidence of the slow growth of this schwannoma, including the smooth expansion of the IAC, with osseous remodeling, deformation of adjacent brain tissue, and a disproportionately small amount of edema, given the size of some this tumor.
On T2-weighted images, this schwannoma appears heterogeneously hyperintense, probably due to regions of compactly arranged cells (Antoni A) mixed with regions of sparsely arranged cells (Antoni B), with variable cellularity and water content.
Concerning features include larger size, brain stem or cerebellar compression, peritumoral edema, hydrocephalus, and tonsillar herniation 1.
Tissue sampling of this tumor revealed schwannoma - pathology-proven vestibular schwannoma.
Case courtesy
- Erick Cavalcante, MD - PGY-3, Radiology Resident, Department of Radiology
- Antonio Rodrigues de Aguiar Neto, MD - Radiologist, Department of Radiology
- Hospital da Restauração – Recife, PE – Brazil
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