Imaging of cerebellopontine angle lesions: an update. Part 2: intra-axial lesions, skull base lesions that may invade the CPA region, and non-enhancing extra-axial lesions

Abstract

Computed tomography (CT) and magnetic resonance (MR) imaging reliably demonstrate typical features of vestibular schwannomas or meningiomas in the vast majority of mass lesions responsible for cerebellopontine angle (CPA) syndrome. However, a large variety of unusual lesions can also be encountered in the CPA. Covering the entire spectrum of lesions potentially found in the CPA, these articles explain the pertinent neuroimaging features that radiologists need to know to make clinically relevant diagnoses in these cases, including data from diffusion- and perfusion-weighted imaging or MR spectroscopy, when available. A diagnostic algorithm based on the lesion's site of origin, shape and margins, density, signal intensity and contrast material uptake is also proposed. Non-enhancing extra-axial CPA masses are cystic (epidermoid cyst, arachnoid cyst, neurenteric cyst) or contain fat (dermoid cyst, lipoma). Tumours can also extend into the CPA by extension from the skull base (paraganglioma, chondromatous tumours, chordoma, cholesterol granuloma, endolymphatic sac tumour). Finally, brain stem or ventricular tumours can present with a significant exophytic component in the CPA that may be difficult to differentiate from an extra-axial lesion (lymphoma, hemangioblastoma, choroid plexus papilloma, ependymoma, glioma, medulloblastoma, dysembryoplastic neuroepithelial tumour).

Imaging findings of extraventricular choroid plexus papillomas: A study of 10 cases

“…Their most frequent location is the lateral ventricle, followed by the fourth and third ventricles (10). Their characteristic MRI appearance has been previously described in a number of studies (4)(5)(6)11).…”

Cerebellopontine angle lipomas: magnetic resonance imaging findings in two cases

“…They may originate from persistence of the meninx primitive, a precursor of pia mater and arachnoid, which develop into fat 4 . Most of the intracranial lipomas are pericallosal asymptomatic lesions found incidentally during neuroimaging studies 6 . On the other hand, the most common extra-axial site of lipomas in the posterior fossa is the CPA 4,7 .…”

“…These tumors are maldevelopmental masses that arise from abnormal differentiation of the meninx primitiva 1,4,5 . Clinically, CPA lipomas can cause slowly progressive neurological symptoms and signs affecting cranial nerves or brain stem 3,[6][7][8] . Because these lesions usually are strongly attached to the surrounding structures, any surgical attempts of complete resection can result in neural or vascular damage, reinforcing the importance of the pre-operative imaging diagnosis [1][2][3]7,9,10 .…”

Cerebellopontine angle meningioma extending into internal auditory canal presenting with unilateral facial weakness and sensorineural hearing loss: Case presentation with review of literature

“…High-spatialresolution Magnetic Resonance Imaging (MRI) is the imaging of choice. Bonneville et al [13][14] reported categorisation of tumours of the cerebellopontine angle (CPA) on the basis of key neuroimaging features on contrast-enhanced MRI, which aid in more specifi c diagnosis and limit the differential diagnosis. Enhancing extra-axial lesions, such as in the case presented here, account for 80% to 95% of CPA tumours.…”

“…This case report describes in detail the clinical fi ndings, typical signal characteristics, more specifi c imaging features such as presence or absence Journal of Kathmandu Medical College Vol. of calcifi cation, a hemispheric or ice-cream-cone shape sign, adjacent hyperostosis, a 'dural tail', extension into one or more skull base neural foramina and enlargement of the IAC, which aids in a more specifi c diagnosis and skilled surgical management [13][14][15][16] .…”