Ependymomas are the third most common type of childhood glioma -- a type of brain and spine tumor. Scientists believe ependymoma tumors develop from the ependymal cells, the cells that line the ventricles (fluid-filled spaces in the brain) and the central canal of the spinal cord. Ependymomas are graded on a sale of I to III and include several subtypes, such as myxopapillary ependymomas, subependymoma, regular ependymoma, anaplastic ependymoma and other variants.