Surgery of the skull base: transcochlear approach to the petrous apex and clivus.

The transcochlear approach is described for resection of lesions arising anterior or medial to the internal auditory canal as well as for those arising directly from the clivus. Through an extended complete mastoidectomy the facial nerve is totally decompressed and re-routed posteriorly from the stylomastoid foramen to the internal auditory canal. The fallopian canal, promontorium, and cochlea are removed anteriorly and medially as far as the internal carotid artery, obtaining exposure to a triangular area limited by the superior petrosal sinus, inferior petrosal sinus, carotid, and internal auditory canal, giving adequate exposure to the structures of the clivus and the midline (basilar artery, vertebral arteries, and the sixth cranial nerves).