1. Infratentorial (70%)

• ependymomas arise from specialized cells that line the ventricular system (typically the 4th ventricle)
• obstructive hydrocephalus results from the local extension of infratentorial tumors into the 4th ventricle
• local extension also occurs via the CSF cisterns to involve the exiting cranial nerves and inferiorly through the foramen magnum

2. Supratentorial (30%)

• these extra-axial tumors arise from ectopic nests of ependymal cells subjacent to the ependymal surface
• incidence increases with age

1. Low-grade form

• most common with 5 yr survival rate: 60-80%
• cells have similar morphology to normal ependymal cells

2. Anaplastic Ependymoma

• most commonly supratentorial
• cells have histologic features of malignancy: high cellularity, pleomorphism, frequent mitosis, necrosis, vascular proliferation
• 5 yr survival rate: 10-30%

3. Ependymoblastoma

• most commonly supratentorial
• considered a PNET variant with ependymal different-iation
• high frequency of dissemination with very poor prognosis: median survival time: 12-20 months

1. Infratentorial

• obstructive hydrocephalus with elevated ICP
• cerebellar signs
• cranial nerve dysfunction with invasion into brain stem
• severe neck pain is pathognomonic due to the unique growth pattern of ependymomas through the foramen magnum into the upper cervical region

2. Supratentorial

• focal neurologic signs with hemiparesis and complex partial seizures
• personality changes

1. Leptomeninges

• especially for infratentorial anaplastic tumors

1. MRI

• T1-weighted images
  • tumors are hypointense with heterogeneous appearance due to cystic areas, vascularity, hemorrhage, or necrosis
• gadolinium enhanced
  • produces a heterogeneous enhancement

2. CT

• more sensitive in the detection of calcifications (occurs in 50% of ependymomas)

3. Neuraxis Staging

• CT myelography
• gadolinium-enhanced MR imaging