Cerebellopontine angle mass
Dr Yuranga Weerakkody and Dr Frank Gaillard et al.
The cerebellopontine angle (CPA) is a relatively frequent site of intracranial masses, many of which are relatively specific for the region.
It is worth dividing cerebellopontine angle masses into three groups, based on imaging characteristics.
- enhancing masses
- masses with high T1 signal on MRI
- masses with CSF intensity / density
Alternativel quick mnemonic to remember the common entities affecting the cerebellopontine angle (CPA) is AMEN or SAME.
Enhancing mass
- acoustic schwannoma : ≈ 80 % of CPA masses (commonest by far)
- meningioma : ≈ 10 % of CPA masses (2nd commonest)
- trigeminal schwannoma
- facial nerve schwannoma
- ependymoma
- metastasis
High T1 signal mass
- haemorrhagic acoustic schwannoma
- neurenteric cyst : usually prepontine, but fluid may be proteinaceous and high on T1
- thrombosed berry aneurysm : often will have calcified rim, and haemosiderin staining.
- white epidermoid : rare, and will restrict on DWI
- cerebellopontine angle lipoma : usually has the facial nerve and vestibulocochlear nerve coursing through it. Will saturate on fat suppressed sequences.
- ruptured intracranial dermoid : often multiple droplets, and original midline lesion can be often seen.
CSF density mass
- epidermoid cyst : ≈ 5 % of CPA masses ( 3rd commonest)
- arachnoid cyst
Other masses
Many other masses can present at or around the cerebellopontine angle. They include:
- primary melanocytic neoplasm
- neurosarcoidosis
- cholesterol granuloma
- paraganglioma
- petrous apicitis
- chondrosarcoma
- chordoma
- endolymphatic sac tumour
- pituitary adenoma
- brainstem glioma
- choroid plexus papilloma
- lymphoma
- haemangioblastoma
- ependymoma
- medulloblastoma
- DNET (dysembroblastic neuroepithelial tumour)
- ganglioglioma (rare 3)
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