Anatomical basis of the extended subtemporal approach to the cerebellopontine angle: its value and limitations.

The cerebellopontine angle is an anatomic region situated deeply at the anterolateral aspect of the brainstem, access to which is complicated by the presence of neurovascular bundles. The functional importance of these cranial n. (trigeminal, facial, vestibulo = cochlear, glossopharyngeal, vagus and accessory) calls for the use of special surgical routes of access in certain cases. In particular, tumors situated between the vestibulocochlear-facial bundle behind and the trigeminal n. in front are difficult to reach by the suboccipital and subtemporal transmeatal routes. The endeavor to preserve hearing in particular situations, where the side opposite the tumor is no longer functional, justifies the use of a subtemporal transmeatal route extended by opening the tentorium cerebelli. This anatomic and experimental surgical study deals with the possibilities of this route of approach.