Ependymoma

1-Age incidence: 10-15 years.

   The second peak at fourth or fifth decades.

2-Ependymoma arises in children in the fourth ventricle while in adult arises supra tentorial.

3-Choroid plexus tumor arises in children supra tentorial while in adult in the fourth ventricle.

4-Ependymoma is the most common tumor arising from the posterior fossa containing calcium.

5-Radiological appearance:

-Iso dense lobulated mass filling the fourth ventricle.

-Calcium is common(50%).

-Cystic changes is common(15%).

-Homogenous or heterogenous enhancement.

-Commonly  associated with supra tentorial hydrocephalus and cerebro-spinal fluid seeding.

-Very important sign for ependymoma is a partially calcified posterior fossa mass extending through the fourth ventricle foramina.

5-The lesion arising from the fourth ventricle results in disappearance of the fourth ventricle.

   The lesion arising from the brain stem compresses the fourth ventricle posteriorly while that             arising from the cerebellum will compresses the fourth ventricle anteriorly.

6-In MRI, it shows hypo intensity in T1, hyper intensity in T2 while in case of contrast injection it causes homogenous to heterogenous enhancement. 

In the sagittal view it gives characteristic appearance where the tumor is casting the fourth ventricle(Taking the shape of the fourth ventricle) with extension into foramina.

7-D.D.:

-Medulloblastoma.

-Choroid plexus papilloma---Arises in the fourth ventricle in adult.

-Epidermoid cyst---Non enhancing lesion.

-Astrocytoma---Usually is a cystic lesion with enhancing nodule.