Endoscopic Paramaxillary Approach to the Infratemporal Fossa and Pterygomaxillary Space

Introduction: Open approaches to the infratemporal fossa (ITF) and pterygomaxillary/pterygopalatine space (PS) include transzygomatic, orbitozygomatic, zygomaticotransmandibular, transmaxillary, facial translocation, and midfacial degloving. Endoscopic approaches to decrease tissue damage include endonasal, endoscopic Gilles' approach, and lateral endoscopic approach with dual ports. Limitations to these approaches include restricted exposure of the ITF and difficult surgical manipulation due the posterior incisions and retrograde endoscopic approach.

The paramaxillary zone is described as the region leading to the ITF and PS and includes the parapharyngeal space and mandibular ramus. In this study, advanced computer modeling was utilized to analyze a new transoral endoscopic approach, the paramaxillary approach. The objective was to combine observations in the operating room with the results of the computer model to determine clinical indications and boundaries of the approach.

Methods: Patients who had lesions in the ITF and PS for which the paramaxillary approach was used were queried within our skull base surgery database. The paramaxillary approach involves use of endoscopic instruments to access ITF and PS through a sublabial incision followed by lateral and superior dissection ([Fig. 1]).

Using 3D Slicer (www.slicer.org), imaging, and operative notes/videos, the average approach trajectory was modeled. Then the boundaries at orthogonal planes to the entrance, midpoint, and superior limit of the model were determined to analyze the full extent of surgical access provided by the paramaxillary approach.

Results: Ten patients who underwent an endoscopic paramaxillary approach for ITF and PS masses were identified (median age, 26 years). The location of each of tumor was segmented ([Fig. 2]). While some lesions originated in the ITF and PS, many had other sites of origin with significant extension into the space, and all were able to be accessed with the paramaxillary approach.

The boundaries of the paramaxillary approach were determined from the measurements of the computer model and operative observations ([Fig. 3]). The approach begins at posterior maxilla, and it can be lateral or medial to the mandibular condyle which allows for variability in endoscopic angles and access more medial PS lesions. The lateral extent is limited proximally only by extent of cheek/soft tissue retraction and is bounded in the middle by the zygomatic arch. The superior limit of dissection is at the temporal line.

Conclusion: The endoscopic paramaxillary approach is a transoral minimally disruptive approach to the ITF and PS that provides excellent surgical exposure for resection of appropriate pathology. It can be used in combination with other approaches for lateral extension of tumors such as juvenile angiofibromas. Compared with previously described endoscopic approaches, there are no external incisions, instruments are able to be used in their intended orientation, and all aspects of ITF and PS can be accessed.

Fig. 1 Left: Operative photo of right-sided paramaxillary approach; transillumination highlights superior extent of access. Right: Endoscopic view of right-sided paramaxillary approach.

Fig. 2 3D model of infratemporal fossa and pterygomaxillary space masses included in the study with histological diagnoses.

Fig. 3 Lateral and base views of 3D model of the paramaxillary approach (purple) with possible locations of endoscope (yellow).

Publication History

Article published online:
12 February 2021