Most of the medulloblastomas occurs in the first decade. It typically develops from the primitive neuroectodermal cells at the roof of the fourth ventricle 2
. Approximately 2/3 of the cases are originated from vermis at pediatric age 3
. The development of this tumor at the cerebellopontine angle may be originated from the residues of external granular layer the cerebellar cortex 4
Spread to pontocerebellar angle (PCA) may be due to the foramen luschka lateral extension or directly exophytic growth of the lesion in the cerebellum or pons. Extraaxial localization without any contact with the cerebellar tissue is quite rare 5.
Regardless of the clinical reflection, it is difficult to distinguish angle medulloblastomas from other tumors located in this region 6.The most common pathologic lesions of cerebellopontine angle are acoustic neurinomas, meningiomas, primary cholesteatomas and epidermoid tumors 7. In our case the tumor was located extraaxially which was extremely rare at pediatric age.
The pathologic lesions of this region are commonly associated with non-specific symptoms such as headache, nausea-vomiting, dizziness and hearing loss 8. Lack of hearing loss and facial paralysis is helpful in distinguishing from acoustic neurinoma, but these symptoms are commonly observed in other PCA tumors 9. The present case had right facial paralysis in the preoperative period.
MR imaging usually shows a heterogeneous-enhancing lesion appearance in clinical terms; however, there may also be a homogenous-enhancing pattern. This may lead to misinterpretation in the preliminary diagnosis. In the present case, the tumor was a homogeneous-enhancing mass in the MR sequences.
The goal of surgical treatment for CPA tumors is histopathological diagnosis, maximum cytoreduction, and restoration of cerebrospinal fluid flow while avoiding brainstem manipulation and cerebellar injury 10. We performed subtotal tumor excision because of peroperative hemorrhage.
Although intracranial medulloblastomas are usually originated from the posterior fossa cerebellar vermis, they may rarely occur at the pontocerebellar angle and extraaxially. Therefore, they may be confused with other tumors such as acoustic neurinoma and meningioma that are frequently seen in this region. This rare localization should be considered during the differential diagnosis.