The ependymoma arises from the ependymal cells lining the ventricular system, especially the fourth ventricle and the central canal of the spinal cord, and less frequantly, in the lumbosacral enlargement and the filum terminale (ependyma of the cauda equina). Like the oligodendroglioma, it is slow-growing, relatively uncommon and represents approximately five per cent of all gliomas.