Tumours of the third ventricle.

Primary intraventricular tumors, including colloid cysts, choroid plexus papillomas, and ependymomas have their attachment within the IIIrd ventricle and stay within its confines. Secondary intraventricular tumours arise adjacent to the IIIrd ventricle, often in the suprasellar region, and include craniopharyngiomas, optic nerve gliomas, and meningiomas. Approaches to the ventricle include subfrontal, subtemporal, anterior transventricular, anterior and posterior transcallosal, and transtentorial routes. Memory problems have been noted with anterior dorsal methods, implicating damage to one or both anterior forniceal columns. Methods of opening the roof of the third ventricle must evaluate risk to the deep ventricular veins, the fornix, and the choroid plexus. The basal subfrontal method may be modified by opening the lamina terminalis or including a lateral approach from the pterional area. The application of these approaches in a series of 100 third ventricle tumours is analyzed.