[The interhemispheric trans-lamina terminalis approach to tumor of anterior part of the third ventricle].

In this paper the authors reported the operative approach to third ventricle tumors, mainly discussing bifrontal translamina terminalis approach. Our principle for approaching to the third ventricle tumors is as follows. If the tumor originates from the upper wall behind the Foramen of Monro, transcallosal approach should be adopted. And if the posterior wall is its origin, either transcallosal or infratentorial approach would be better. But if the tumor arises from the anterior half of the third ventricle, translamina terminalis approach should be adopted. In trans-lamina terminalis approach, at first bifrontal craniotomy should be performed. The interhemispheric space of the frontal lobes is dissected and lamina terminalis is cut, then the tumor can be reached. If necessary, the anterior communicating artery can be cut, and/or the optic chiasma can be cut for extending the operative field if the optic nerve is irreversibly damaged. There are several advantages in this approach. First, we can expose the main arteries and the operative filed is wide enough, making the operative procedure safe. Secondly, as comparing to the conventional approaches, any cortical incision or excision is unnecessary. By cutting the lamina terminalis which is usually thin and expanded as a result of hydrocephalus, even a large tumor can be removed. Also lethal complication is avoidable, because this approach has less possibility to damage the lateral wall of the third ventricle. This approach can be applied not only to the tumor but also to AVM or giant aneurysm adjacent to the third ventricle.