The Extra-axial Cerebellopontine Angle Medulloblastoma in an Adult Patient: A Case Report and Review of Literature

Background and Importance:

 Medulloblastoma (MB) is regarded as a scarce primary brain neoplasm in adulthood, originating from the fourth ventricle or the cerebellum, and cerebellopontine angle (CPA)-MB has been described less often in the literature. Few cases of CPA MB have been reported in the English-written literature, most of which are intra-axial, mainly in children; adults' extra-axial CPAMB is even scarcer. To the best of the authors’ knowledge, 12 cases of extra-axial CPA MBs have been reported in the English-written literature.

A 23-year-old man presented to our center complaining of a generalized pulsatile headache, imbalance, swallowing impairment, and right-sided hearing loss for the past 20 days. Computed tomography (CT) scan of the brain showed a hyper-dense extra-axial mass lesion (41*37mm) in the right CPA with a significant compression effect on the fourth ventricle, causing a three ventricular obstructive hydrocephalus. Magnetic resonance imaging (MRI) showed a well-defined heterogeneous extra-axial, lobulated, dural-based mass lesion in the right CPA, hypointense on the T1 sequence, and hyperintense on the T2 sequence compared with the adjacent parenchyma, which has a bright heterogeneous enhancement during gadolinium injection. A significant mass effect was observed on the adjacent parenchyma, brain stem, and fourth ventricle without evidence of parenchymal edema. The patient underwent emergent surgery the next day regarding the mass effect and hydrocephalus. On the postoperative examination in the intensive care unit, no new neurological deficit was detected, and the swallowing and gag reflex significantly improved.

Though rare, clinical considerations, along with early supportive radiologic measures, should be considered in subjects with suspected MB. A total tumor excision approach followed by aggregative chemotherapy/radiotherapy is designed to hinder tumor relapse.