Adult Cerebellopontine Angle Medulloblastoma Originating in the Pons Mimicking Focal Brainstem Tumor

We herein report a rare case of cerebellopontine angle (CPA) medulloblastoma originating in the brainstem that demonstrated a very unusual clinical presentation and radiological appearances. A 25-year-old female was admitted to our hospital with a right hearing disturbance and a right facial palsy. A small non-enhanced lesion having minimal mass effect in the right CPA was identified by using a 1.5-tesla-MR system, whose size remained almost unchanged a year. The 3-tesla MR images revealed that the precise region was in the right side of the tegmentum of the lower pons to the inferior cerebellar peduncle and the flocculus. MR spectroscopic images using a 3-tesla system revealed a high ratio of choline-to-N-acetylaspartate in the region of interest in comparison to the contra-lateral side. Craniotomy and biopsy were performed. The histopathological diagnosis was medulloblastoma. The patient received craniospinal irradiation and chemotherapy, and achieved complete remission by the time of the follow-up MR images. She is now doing well with a full recovery of the right facial palsy. MR spectroscopic imaging is considered to be quite useful for the management of this rare type of brainstem tumor. J Neuroimaging 2009;19:385-387.