Cerebellar medulloblastomas (MBs) are one of the most common posterior fossa tumors in children but rarely occur in the cerebellopontine angle (CPA).

Meduloblastomas arise from the roof of the fourth ventricle and superior medullary velum but the origin of the CPA region medulloblastomas is not certain and there have been several hypotheses. Among the suggestions are lateral extension of tumour from the fourth ventricle through the foramen of Lushka, or direct exophytic growth from the site of origin at the surface of the cerebellum or pons ¹⁾.

Their development in the CPA may be from the remnants of the external granular layer in the cerebellar hemisphere, including the flocculus which faces the CP angle ²⁾.

There are only few reported cases of cerebellopontine (CP)-angle medulloblastoma in the literature, with most being intra-axial. The extra-axial site of this tumor remains a rarity ^{3) 4) 5)}.

Only 39 cases of CPA MBs were reported in the literature, and most of them were classic and desmoplastic MBs ⁶⁾.

The patients commonly presents with cerebellar symptoms or symptoms of raised intracranial pressure (ICP) due to hydrocephalus. Diminution of hearing or facial asymmetriness is uncommon. In the literature review, only two cases had seventh and eight nerve palsies as the presenting symptoms as in the case of Nyanaveelan et al ⁷⁾.

Jaiswal et al., have treated 14 cases of CPA medulloblastomas. This is first and the largest series of CPA medulloblastomas reported in the world literature ⁸⁾.

Four of the total 63 cases of medulloblastoma managed in the Department of Neurosurgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow - 226014, India between 1988 to 1998, presented with a mass in the cerebellopontine angle. There were two children amongst these four patients, aged eight and nine years. The other two patients were young adults. Three patients had primary CPA medulloblastoma, while the fourth case had a recurrence in this region, following the excision of the primary vermian tumour. All the four cases were managed by gross total microsurgical excision and craniospinal irradiation. One of the two children, developed subfrontal recurrence after 1 year and 8 months of initial treatment, while the other child developed a large recurrence at primary site, within three months of post-operative irradiation. However, the adult patient developed CPA recurrence and subsequent cervical intramedullary metastasis within two and a half years of diagnosis. These three cases succumbed to their disease, between three months to thirty months of their initial management. However the fourth patient, a 20 years female with desmoplastic variant, was well at two and a half years of follow up ⁹⁾.

A 22-month-old girl presented with progressive cerebellar ataxia. Magnetic resonance imaging showed a large tumor in the right CPA and obstructive hydrocephalus. Surgical resection was performed and achieved total tumor removal. Microscopic examination and immunohistochemical staining revealed the diagnosis of MB with extensive nodularity. The patient recovered from her symptoms during follow-up and was transferred for adjuvant chemotherapy.

MB should be considered as a differential diagnosis of a lesion in the CPA. The treatment and outcome of CPA MBs are similar to cerebellar MBs ¹⁰⁾.

A 23-year-old male patient with a two month history of deafness, nausea, vomiting and ataxia is presented. Clinical and radiological findings demonstrated a heterogeneously enhanced extra-axial lesion in the right CP angle. Total excision was performed and the histopathological features of medulloblastoma were confirmed. After surgery, the patient had no neurological deficit and the audiometric findings were improved. In addition, he underwent adjuant radiotherapy and no sign of metastatic mass was observed in follow-up spinal cord MRI. Although extremely rare, medulloblastoma must be considered in the differential diagnosis of extra-axial CP angle lesions ¹¹⁾.

The patients were a 22-year-old man and a 26-year-old woman with a mass developing in the CPA. The preoperative radiological diagnosis was vestibular schwannoma in the first case and petrosal meningioma in the second case. The patients were operated on through a retrosigmoid approach. The intraoperative findings revealed an intra-axial tumour and the histological diagnosis was classic type of MB in both cases ¹²⁾.

Extra axial adult cerebellopontine angle medulloblastoma: An extremely rare site of tumor with metastasis ¹³⁾.

Cugati et al., ¹⁴⁾.

Fallah A, Banglawala SM, Provias J, Jha NK. Extra-axial medulloblastoma in the cerebellopontine angle. Can J Surg. 2009 Aug;52(4):E101-E102. PubMed PMID: 19680492; PubMed Central PMCID: PMC2724820 ¹⁵⁾.

An extremely rare case of a right cerebellopontine angle medulloblastoma in a five year old Malay girl which had eroded into the petrous bone and extended into the temporal fossa is reported. Combined subtemporal and retromastoid approach to achieve gross total surgical resection was achieved followed by radiotherapy and chemotherapy ¹⁶⁾.

A 40 year old man presented with a 3 weeks history of headache, morning vomiting and left hearing difficulties. Magnetic resonance imaging revealed a left cerebellopontine angle (CPA) tumor, like a well circumscribed homogeneously enhancing mass. Through a left suboccipital craniectomy the tumor was totally removed. It presented as a cerebellopontine angle tumor, like a meningioma, and not as an intra-axial tumor. Histological analysis revealed that the tumor was composed of densely packed with highly proliferative cells that produce a dense intercellular reticulin fiber network. Inmunohistochemical analysis showed positive expression to synaptophysin, specific neuronal enolase and cromogranin. Histological diagnosis was crucial to define it as a desmoplastic medulloblastoma the present case and to perform postoperative adjuvant therapy. Neurosurgeons should be aware of the possibility that a CPA tumor is of intraaxial origin, because this increase the variability on pathological diagnosis ¹⁷⁾.

A 21-year-old male patient presented with a rare cerebellopontine angle medulloblastoma manifesting as cerebellar and long tract involvement signs and symptoms. The clinical and radiological characteristics of the lesion were similar to extraaxial lesions of cerebellopontine angle. The histological diagnosis of the lesion was medulloblastoma. Surgery achieved partial removal and was followed by radiotherapy and chemotherapy. The patient remained well after 18 months. Medulloblastoma of the cerebellopontine angle is a relatively rare clinical entity and may occur as a dural-based extraaxial mass ¹⁸⁾.