Inferolateral Transorbital Approach to the Petrous Apex. An Adjunctive Approach to the EEA

Introduction: Many approaches to reach the petrous apex have been used open as well as endoscopic and more recently, endoscopic ear surgery approaches. However, there is a lot of morbidity and access limitation with anterior endoscopic endonasal approaches regarding lateral access with probable need to excise the eustachian tube, jeopardizing the middle ear aeration and probable delayed complications.

Aim of Work: Providing a safe corridor to completely eradicate tumors that arise and/ or extend into the petrous apex laterally trying to spare the eustachian tube and avoiding unnecessary complications to the middle ear.

Materials and Methods: Five cadaveric latex injected heads were used in the study Nora define landmarks and properly describe the Corredor as required. The trigeminal ganglion lies anatomically on top of the petrous apex on the anterior and middle portions of it, two branches (V2 and V3) pierce the pterygoid process to reach the pterygopalatine, and infratemporal fossae. An inferolateral transorbital approach was used to gain access to the maxillary sinus, ION was traced posteriorly to reach foramen rotundum, posterior maxillary wall is dissected, periosteal covering of the pterygoid base at the lateral side of foramen rotundum is identified, and the lateral pterygoid plate is dissected inferiorly subperiosteally, going superiorly to reach foramen ovale and V3. Posterior dissection is continued and performed till the eustachian tube is identified. Bleeding from the pterygoid plexus can be controlled by Surgiflo, if encountered.

Fig. 1 Showing the space between v2 and v3.

By tracking v2 to its origin in the trigeminal ganglion, a point between v2 and v3 is reached using an anterolateral trajectory.

Drilling the lateral pterygoid plate is done in an inferolateral fashion superior to the eustachian tube, which can provide a safe corridor to remove the lesions extending all the way into the posterior part of the petrous apex till the carotid genu if needed.

Fig. 2 Transorbital view of the space between v2 and v3 and drilling of the petrous apex following drilling.

Careful drilling of the lateral pterygoid plate inferior to foramen ovale in a posteromedial trajectory (identifying and preserving the anterolateral and inferior surfaces of Meckel's cave) toward the eustachian tube is done. In this fashion any lesion lateral to Meckel's cave posterior or superior to the cartilaginous part of eustachian tube is detected, eradicated and cleared.

The distances between foramen ovale, foramen rotundum, posterior genu of ICA, eustachian tube are measured and used as landmarks if needed.

Results: The inferolateral transorbital corridor to petrous apex can be a safe, efficient addition as an adjunctive technique to eradicate laterally located lesions of the petrous apex or extending into it from the petroclival fissure sparing the eustachian tube, maximizing surgical dominance and tumor control.