Exophytic Brain Tumors Mimicking Primary Lesions of the Cerebellopontine Angle

Abstract

The vast majority of cerebellopontine angle (CPA) tumors are extraaxial masses arising from either the eighth nerve (acoustic neuroma) or meninges (meningioma). Rarely, a tumor that arises from the brain parenchyma may protrude laterally to present with a clinical and radiographic picture simulating that of the much more common extraaxial lesions. Three individuals with CPA lesions that ultimately proved at operation to be exophytic brain tumors (pontine medulloblastoma, cerebellar astrocytoma, and fourth ventricular ependymoma) are described. The clinical manifestations of these lesions, although not entirely typical, fell well within the possible range of presentation of benign tumors primary to the CPA. In two of these cases the tumor actually penetrated into the internal auditory canal. As the optimal management strategy for treating parenchymal tumors differs substantially from that for extraaxial lesions, it is essential that the surgeon have a preoperative awareness of the lesion's nature before embarking on a surgical endeavor. Critical to arriving at the correct diagnosis is the close examination of preoperative imaging studies. The clinician should be alerted to the possibility that a CPA tumor is of intraaxial origin when the preoperative magnetic resonance imaging scan shows 1) blurring of the margin between the tumor and brainstem or cerebellum; 2) a degree of peritumoral hyperintensity on T2-weighted scans disproportionate to the size of the extraaxial mass; and 3) dilation of the lateral recess of the fourth ventricle.

Medulloblastoma of the Cerebellopontine Angle-Case Report-

“…16,27,28) Medulloblastomas may grow to occupy the CPA through two pathways: lateral extension from the fourth ventricle through the foramen of Luschka, or direct exophytic growth from the site of origin at the surface of the cerebellum or pons. 1,21) Although the lesion in our patient originated from the lateral surface of the cerebellum, the exact site of origin could not be verified.…”

“…The short duration of symptoms and rapid progression to brainstem dysfunction and hydrocephalus are suggestive of a parenchymal lesion rather than an extraaxial tumor of the CPA. 1,8,15) The goals of surgical treatment for medulloblastomas are histological confirmation of the diagnosis, CPA Medulloblastoma maximum cytoreduction, and the restoration of cerebrospinal fluid pathways. 31) To achieve maximum cytoreduction, further aggressive tumor resection from the brainstem is not advised 31) and a high postoperative complication rate of up to 26% has been reported following tumor resection.…”

“…8,14,18,19) CPA medulloblastomas are relatively rare lesions. 1,7,8,20,22,34) We treated an adult patient with a CPA medulloblastoma, and discuss the clinical and radiological differential diagnostic features of the lesion.…”

Medulloblastoma of the Cerebellopontine Angle in a Child: A Rare Entity

“…There are no pathognomonic MRI criteria for differentiating them, and the only characteristic found is an iso-or hypointensity on T2/FLAIR sequence. [8][9][10][11][12][13][14][15] MB has variable appearances on MRI in both children and adults. 4 In most reported cases, CPA MBs have a homogeneous hypointensity on T1-, a heterogeneous hyperintensity on T2/FLAIR and enhance heterogeneously and strongly after contrast.…”

Metastase eines spinalen myxopapillären Ependymoms im inneren Gehörgang

“…Unter ihnen kommen Meningeome (5-15%), primäre Cholesteatome (3-5%), Glomus-jugulare-Tumoren (1-3%) und Fazialis-oder Trigeminusneurinome (1-2%) am häufigsten vor. Seltener finden sich Arachnoidalzysten,Haemangiome,Lipome,Lymphome, Metastasen, andere ZNS-Malignome, Granulome und Ependymome [1,6,11].…”