Ependymomas are glial tumors (glial cells are the supporting cells of the brain and spinal cord and ependymal cells are a subtype of glial cells) that originate from the ependymal cells that line ventricles of the brain and central canal of the spinal cord. The ventricles and central canal are naturally occurring cavities within the brain where cerebrospinal fluid is normally produced. Epenymomas usually arise from the ependymal tissue on the floor of the 4th ventricle in children or in the spinal cord in adults. They can also arise in a variety of other locations throughout the brain and spine. Epenymomas often lead to obstruction of the cerebrospinal fluid flow within the brain because of their intimate relationship with the ventricles, central canal and spinal fluid.
Ependymomas are sub-divided and pathologically graded into four major types: subependymomas and myxopapillary ependymomas (grade I), and ependymomas (grade II) and anaplastic ependymomas (grade III). The grade is based on how much the cells look like normal ependymal cells, although various grading systems exist. The cells of a grade I ependymal tumor look somewhat unusual, and those of a grade III tumor appear pleomorphic and more invasive to the surrounding tissue.
Subependymomas usually occur along the walls of a ventricle and are slow growing and considered to be low-grade or grade I tumors. Myxopapillary ependymomas tend to occur in the lower part of the spinal cord near the conus medullaris, which is essentially the tail end of the spinal cord. This part of the spinal cord is important in controlling bowel and bladder function as well as some lower extremity function. Both of these ependymoma subtypes are slow growing and are considered to be low-grade or grade I tumors.
Ependymomas are the most common ependymal tumors and are considered grade II tumors. These tumors are usually located along or adjacent to the ventricular system and often in the 4th ventricle near the brain stem and the upper portions of the spinal cord. These tumors can often lead to hydrocephalus where there is a backup of the spinal fluid within the venrticles of the brain.
Anaplastic ependymomas are high-grade tumors (grade III) and tend to be faster growing than the lower grade ependymal tumors. Similar to grade-II ependymomas, these are often located along or adjacent to the ventricular system and often in the 4th ventricle near the brain stem and the upper portions of the spinal cord.