Dural-Based Posterior Fossa Medulloblastoma Mimicking a Petrous Meningioma in Late Adulthood.

Medulloblastoma of the posterior fossa is commonly encountered in pediatric populations but rarely reported in adults. Adult cases of medulloblastoma typically occur in younger patients, tend to arise intra-axially within the cerebellar hemisphere, and usually exhibit classic histopathologic features. A 54-year-old male presented with headaches, dizziness, gait instability, and frequent falls that had worsened during the prior 3 months. Imaging and histopathologic analysis revealed extra-axial, dural-based posterior fossa medulloblastoma with desmoplastic/nodular histopathology, mimicking a petrous meningioma. The mass occupied the left cerebellopontine angle. The patient underwent microsurgical gross total resection of the tumor followed by proton beam radiation therapy and was disease-free at 1-year follow-up. Few dural-based posterior fossa medulloblastomas resembling petrous meningiomas have been reported, and to our knowledge, this is the first description of a case to be treated successfully with proton beam therapy in an older adult. Although rare, medulloblastoma can occur extra-axially in the cerebellopontine angle of older adults, potentially mimicking a petrous meningioma. This rare possibility should always be kept in mind, especially if expectant, nonsurgical management is being considered. To optimize outcome, posterior fossa medulloblastoma should be treated with aggressive microsurgical resection followed by radiation therapy. When available, proton beam therapy should be considered.