16 Infratemporal Fossa Approach

The infratemporal fossa is a deep space of the upper neck that lies inferiorly to the middle cranial fossa, medially, and the zygomatic arch and temporal fossa, laterally. It is bounded by the posterolateral maxillary wall (also called maxillary tuberosity) anteriorly, the greater wing of the sphenoid bone and squamous portion of the temporal bone superiorly, the lateral pterygoid plate medially, the mandibular ramus laterally, and the upper parapharyngeal space posteriorly. Inferiorly, the infratemporal fossa narrows progressively and ends at the medial surface of the mandibular angle, following the direction of the medial pterygoid muscle. The masticatory space, which is the space including the masticatory muscles, is enveloped in the doubling of the superficial sheet of the deep cervical fascia in the masseteric and deep temporal fascial laterally, and the interpterygoid fascia medially. Consequently, the infratemporal fossa contains the deep portion of the masticatory space, which includes the pterygoid muscles, and the caudal portion of the temporal muscle along with several neurovascular structures. The infratemporal fossa communicates medially with the pterygopalatine fossa through the pterygomaxillary fissure, which is in continuity with the inferior orbital fissure, cranially. ^{1 , 2}

Several lesions can primarily originate in the infratemporal fossa, which can also be invaded by tumors arising from contiguous compartments (i.e., parapharyngeal space, sinonasal tract, skull base). Primary lesions can have either a slow, expansive pattern of growth (e.g., schwannomas and juvenile angiofibromas) or an aggressive, infiltrative behavior like malignant tumors (e.g., adenoid cystic carcinomas, adenocarcinomas, chondrosarcomas, and soft-tissue sarcomas). ³ The transnasal endoscopic infratemporal fossa approach has been employed as sole access or in combination with other transnasal or extranasal corridors to manage juvenile angiofibromas, ^{4 – 6} schwannomas, ^{4 , 5 , 7 – 9} maxillary/nasopharyngeal tumors with posterolateral extension, ^{4 , 5 , 10} meningiomas, ^{4 , 11} and other rare lesions affecting the retromaxillary areas. ^{4 , 5}

The first step of the transnasal endoscopic approach to infratemporal fossa consists of exposing the posterolateral wall of the maxillary sinus. To obtain an adequate exposure of the retromaxillary areas, an endoscopic medial maxillectomy, which is detailed in Chapter 5, is therefore required. The removal of structures making up the medial and anterior maxillary walls can be modulated based on the need for mediolateral and craniocaudal exposure. ¹² Performing posterior septectomy or creating a transseptal window can be of some use when approaching the infratemporal fossa, enabling a diagonal trajectory of dissection that facilitates the exposure of far lateral structures. ^{13 – 15} A thorough knowledge of bony landmarks within the maxillary sinus is of utmost importance to adequately tailor the removal of the posterolateral bony wall. In particular, the infraorbital nerve can be adopted as the main reference to guide the resection of the posterolateral wall. The cross that is formed by the horizontal line parallel to the infraorbital canal and the vertical line passing at the posterior end of the canal can be used to schematize transmaxillary approaches. Considering this imaginary landmark, the lower lateral quadrant can be considered the door toward the infratemporal fossa, while the upper medial, lower medial, and upper lateral quadrants lead to the middle cranial fossa, pterygopalatine fossa, and orbital cavity, respectively.

In this chapter, three corridors of dissection within the infratemporal fossa are presented. ¹⁶ The first (lateral) corridor exposes the coronoid process, passing through the temporal muscle. The second (middle) corridor reaches the anterior aspect of the temporomandibular joint exploiting the connective space between the temporal and lateral pterygoid muscles, where the internal maxillary artery runs. The third (medial) corridor exposes the mandibular nerve, middle meningeal artery, and the posterior aspect of the temporomandibular joint via the space that is obtained detaching the lateral pterygoid muscle from the lateral pterygoid plate. Therefore, the most important structure that guides the dissection through the infratemporal fossa is the lateral pterygoid muscle, whose medial and lateral surfaces lead to the most important neurovascular structures of this area.

Related posts:

1 Classification of Endoscopic Transnasal Approaches to the Skull Base and Adjacent Areas 9 Transsellar Approach 10 Transsellar Transdorsal Approach 17 Medial Transcavernous Approach 18 Lateral Transcavernous Approach 21 The Suprapetrous (Meckel’s Cave) Approach

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