How do posterior fossa tumors differ between adults and children?
Posterior fossa tumors are more common in children (approximately 50% to 70% of all brain tumors) than in adults.
Pediatric tumors include medulloblastoma, pineoblastoma, ependymomas, primitive neuroectodermal tumors (PNETs), and astrocytomas of the cerebellum and brain stem.
Cerebellar astrocytoma presents as a laterally located cyst with a well-defined solid component, either in the vermis or cerebellar hemisphere.
Low-grade brainstem gliomas may also occur.
PNETs originate from undifferentiated cells in the subependymal region in the fetal brain. Medulloblastomas often fill the fourth ventricular space and infiltrate surrounding tissue.
In adults, extra-axial tumors are more common and include vestibular schwannomas (the most common cerebellopontine angle mass), meningiomas, choroid plexus papillomas, solitary fibrous tumors, and epidermoid cysts.
Schwannomas are associated with neurofibromatosis type 2, and bilateral vestibular schwannomas are diagnostic of this condition. Intra-axial tumors include hemangioblastomas (the most common adult primary intra-axial posterior fossa mass), lymphoma, ganglioglioma, Lhermitte–Duclos disease, and metastases.