Ependymoma: A rare group of glial tumors that typically arise within or near to the ependymal lining of the ventricular system. These are generally considered slow growing tumors of children and young adults. They are most common in the fourth ventricle.

Epidemiology: Ependymomas are often a disease of young children with a mean age of diagnosis of 4 years.  Ependymomas account for less than 10 percent of tumors arising in the central nervous system and 25 percent of primary tumors originating in the spinal cord.

Risk Factors: No definite risk factors are known although the simian virus 40 was previously suspected.

Symptoms: Children may present with a history of lethargy, headaches, nausea and vomiting. Seizures are often a presenting symptom as well as focal neurological deficits.  However, presenting symptoms will of course vary based on the age of the child and size and location of the tumor.

Differential Diagnosis: Astrocytoma, Medulloblastoma, Brainstem Tumors, Choroid Plexus Tumors, Glial Tumors.

Investigations: Intracranial and spinal ependyomas are usually well visualized on either CT or MRI

Treatment: The treatment of ependyoma is resection which may be followed with a course of radiotherapy. The role of chemotherapy is not as well defined.

 Imaging Findings
Best imaging tool: MR with contrast
- Heterogenous signal
- Indistinct border with floor of fourth ventricle
- Majority infratentorial: originates in fourth ventricle but is soft and can squeeze out into cisterns
- 1/3 supratentorial in periventricular white matter
- On CT, may see calcification, cysts, hemorrhage; hydrocephalus may be seen
- On T1, heterogenous, iso- to hypointense, hyperintense if calcium or hemorrhage
- On T2, heterogenous, iso- to hyperintense; cysts are hyperintense
- On FLAIR, hyperintense to CSF, and cysts are hyperintense

Case #1. Large ependymoma on axial T2 TSE.