Transorbital Approach to the Internal Carotid Artery—A Novel Adjunctive Approach to the EEA

Introduction: The EEA in the recent years has largely replaced many of the more morbid techniques to remove lesions in the midline of skull base. The extended EEA approaches to the coronal plane has helped a lot to gain access to lesions in that are around the anterior genu of the internal carotid artery. However, lesions extending lateral and posterior in the petrous bone toward the posterior genu, are a lot more challenging and almost non accessible by EEA.

Aim of Work: To have a new technique adjunct to the EEA to help eradicate lesions with extension toward the posterior genu with minimal morbidity.

Materials and Methods: Four cadaveric latex injected heads were used in this study where landmarks and measurements were taken to gain a safe access to the posterior genu of the internal carotid artery. An inferolateral transorbital approach was performed, the posterior wall of the maxillary sinus was dissected, identification the lateral pterygoid plate was done, subperiosteal dissection of the infratemporal fossa muscles was done starting at the inferior part of the lateral pterygoid plate going superior and lateral till the TMJ muscle attachment is reached. Identifying the foramen ovale and foramen spinosum is done, the middle meningeal artery is identified, dissected, and coagulated, and the mandibular nerve is identified, dissected, and secured. Sacrificing the nerve was done to take the measurements, but it is not required for the approach. Further dissection is done posteriorly until the lateral pterygoid plate posterior rim is reached and the sphenoid wing is identified superiorly. And the eustachian is identified inferomedially. Drilling of the petrous bone posteromedial to the foramen spinosum in making the (Ali triangle) the apex is the foramen spinosum the anterior border is the line joining the foramen spinosum and the eustachian tube inferiorly, the posteromedial border is the line from foramen spinosum to the posteromedial junction of the pterygoid plate and the greater wing of sphenoid. Drilling is started using a 3-mm diamond burr in a fashion directed inferomedially, taking in consideration that laterally and superiorly to the described triangle the middle ear and lateral surface of the posterior genu of the ICA is located. The distances between the different available landmarks (foramen ovale to spinosum, foramen spinosum to the posterior genu, and TMJ to the posterior genu) were measured in the four heads used in the study.

Results: The transorbital corridor to the posterior genu of the ICA can be a valuable addition for safe and proper access of the lesions extending posterolateral surrounding the petrous ICA. It can serve as an adjunctive port to allow tumor eradication in petroclival tumors as chondrosarcomas.