Trans-cochlear approach

Fig.1 Right side approach. After blind closure of the outer ear canal is performed the extracranial course of the facial nerve is identified, just out of the stylomastoid foramen.

Fig.2 Cortical mastoidectomy is performed with boundaries: tip of the mastoid, posterior edge of the outer ear canal (landmark: the spine of Henle), Asterion.

Fig.3 The mastoid antrum is identifed.

Fig.4 The sigmoid sinus is skeletonized.

Fig.5 The tegmen tympany is drilled and middle fossa dura (MFD) exposed. Part of the labyrinth is already exposed (lateral semicircular canal).

Fig.6 The auditory ossicles are removed from the tympanic cavity.

Fig.7 The bony labyrinth is fully exposed. The superior semicircular canal is opened. The tympanic segment of the facial nerve is identified.

Fig. 8. Lateral and posterior semicircular canals are identified. The course of the facial nerve could be followed just below the lateral semicircular canal. Its segments (tympanic and mastoid) are shown.

Fig.9 The facial nerve course –mastoid segment is shown here. Chorda tympany is also identified.

Fig.10 The tympanic cavity is drilled. The cochlea is skeletonized.

Fig.11 The petrous portion of the internal carotid artery (ICA) is exposed.

Fig.12 Final view.