Far Medial Transoral Approach to the Infratemporal Fossa: An Anatomic Feasibility Study for a Multiportal Approach to the Infratemporal Fossa

Background: Various disease processes affect the infratemporal fossa (ITF), including malignant and benign pathologies. Traditional approaches to the ITF are associated with significant morbidity because of the complex anatomy of this region which limits surgical access to this region, and; therefore, requires extensive and complex approaches. Multiple approaches to the ITF have been described including open lateral skull base approaches and transnasal endoscopic approaches. In this cadaveric study, we describe the nuances of a far medial transoral endoscopic approach to the ITF as a minimally invasive option to access the ITF.

Objective: This study aims to demonstrate the surgical anatomy of a far medial transoral approach to the ITF. This study aims to describe surgical corridors for an endoscopic-assisted approach, and in so doing describe the anatomic relationships of the key neural, vascular, muscular and skeletal structures of the ITF. This study also aims to describe the anatomic limitations of this approach.

Methods: A total of eight infratemporal fossae, in four adult human cadaveric specimens, which had been previously injected with red- and blue-colored latex, were dissected. A far medial transoral endoscopic approach was used to access the ITF. Dissection was done under direct visualization using 0- and 30-degree endoscopes. The relationships of the key structures of the ITF were documented with high-definition images using a Storz AIDA system. Image guidance navigation was also used to describe limits of dissection.

Results: Transoral endoscopic-assisted dissection of the infratemporal fossa may be conceptually divided into two triangular corridors; the superior-medial triangle and the inferior lateral triangle. The superior-medial triangle is bounded by the lateral pterygoid plate and the posterolateral maxillary sinus wall medially, the greater sphenoid wing superiorly and the lateral pterygoid muscle laterally and inferiorly. Dissection of this triangle allows access to the pterygomaxillary fissure, the terminal branches of the maxillary artery, pterygoid plexus, the eustachian tube, and the foramen ovale. The inferior-lateral triangle is bounded by the lower head of the lateral pterygoid muscle superiorly, the superficial head of the medial pterygoid inferiorly and the mandible laterally. Dissection of this triangle allows access to the lower branches of the mandibular nerve, maxillary artery, the post styloid space, the deep lobe of the parotid gland, and the retromandibular vein.

Conclusion: This cadaveric study shows that the far medial transoral approach allows access to all critical structures of the ITF including to the retromandibular region and the poststyloid parapharyngeal spaces posteriorly, the pterygoid plates medially, the mandible laterally, the sphenoid wing superiorly, and the parapharyngeal and deep neck space inferiorly. The endoscopic-assisted transoral endoscopic approach may be a surgically viable option for management of select pathologies of the infratemporal fossa either on its own or in combination with another approach.