Ependymoma are tumours that arise along the lining of fluid-filled cavities of the brain. Most often, these are midline lesions that originate from the ventricular floor. Attachment is commonly observed at the level of the obex, where the fourth ventricle ends and the spinal canal begins. These tumours commonly extend into the foramina of Lushka, growing towards the cerebellopontine angle and extending caudally along the upper cervical spine.

A major distinction that should be made when classifying the tumour is whether it is an infratentorial or a supratentorial tumour (table below). Infratentorial tumours arise from the roof, floor, or lateral resources of the fourth ventricle. These may grow to occlude the fourth ventricle and extend cephalad into the aqueduct. The tumour may also grow caudally through the foramen magnum and into the upper cervical spinal cord. It may also grow through the foramina around the brainstem and into the cerebellopontine angle.

Conversely, supratentorial ependymomas arise from the ependymal lining of the lateral and third ventricles. The tumour may be totally or partially intraventricular, and has a predilection for frontal, temporal, and parietal lobes, as well as for the third ventricle.

There are also differences between those tumours that arise in adults and those in young children. 75% of adult ependymomas arise in the spinal cord. In young children, most ependymomas arise in the fourth ventricle. With increasing age, supratentorial locations become more common.

Table 2. Infratentorial vs. Supratentorial Ependymomas