A Comparative Analysis of Endoscopic-Assisted Transoral and Transnasal Approaches to Parapharyngeal Space: A Cadaveric Study

Abstract

Surgical resection of parapharyngeal space (PPS) tumors is very challenging. An endoscopic-assisted surgical approach to this region requires detailed and precise anatomic knowledge. The main purpose of this study is to describe and compare the detailed anatomy of the PPS via transnasal transpterygoid (TP) and endoscopic-assisted transoral (TO) approaches. Six fresh injected cadaver heads (12 sides) were prepared for dissection of the PPS via TP and TO approaches. Computed tomography (CT) with image-based navigation (Navigation System II; Stryker, Kalamazoo, Michigan, United States) was used to identify bony structures around the PPS. TP and TO approaches could both expose the detailed anatomical structures in the PPS. The TP approach can provide a direct route to the upper PPS, but it is limited inferiorly by the hard palate and laterally by the medial and lateral pterygoid muscles. However, the TO approach can provide a direct route to the lower PPS, but it is difficult to expose the area around the Eustachian tube. The styloglossus and stylopharyngeus muscles could be considered as the safe anterior boundary of the parapharyngeal internal carotid artery (ICA) with the TO approach. Dissection between the stylopharyngeus muscle and the superior pharyngeal constrictor muscle provides direct access to the parapharyngeal ICA. The TP and TO approaches provide new strategies to manage lesions in the PPS. The important neurovascular structures of the PPS could be identified with these approaches. The endoscopic-assisted TO approach can provide direct access to the parapharyngeal ICA.

Endoscopic transnasal transmaxillary approach to the upper parapharyngeal space and the skull base

“…Each cadaveric head was injected with colored silicone; red silicone for the arterial system and blue for the venous system. Endoscopes (0° and 30°) coupled with a high-definition camera and an AIDA HD system (Karl Storz GmbH and Co.) were used to provide excellent visualization [3]. Stepwise dissection via the combined endoscopic transnasal and anterior transmaxillary approach was performed to present the landmarks of the upper PPS and the middle skull base.…”

“…Retracting the MPM and TVPM laterally was helpful to expose the levator veli palatini muscle (LVPM). The soft tissue between the TVPM and superior pharyngeal constrictor muscle was removed to expose the medial space of upper PPS, as described in our previous report [3]. The medial space of the upper PPS was dissected posteriorly to access the poststyloid compartment.…”

“…The deep location of the PPS presents challenges in terms of diagnosis and management. The treatment of lesions arising from the upper PPS is challenging and usually requires an extended approach to avoid injury to adjacent neurovascular structures [1][2][3]. Traditionally, tumors arising from the PPS have been managed through a variety of lateral approaches, including transcervical, transoral, mandibular swing, transparotid, transmastoid, and infratemporal fossa (ITF) approaches and their combinations [4,5].…”

“…Sun and his colleagues compared the detailed anatomy of the PPS observed via transnasal transpterygoid and endoscopic-assisted transoral approaches [3]. However, the detailed endoscopic anatomy of the upper PPS from an endoscopic standpoint is still poorly understood; thus, the purpose of this study was to present the endoscopic anatomy of the upper PPS observed through a combined endoscopic transnasal and anterior transmaxillary approach and to further illustrate its clinical application.…”

A minimally invasive endoscopic transnasal retropterygoid approach to the upper parapharyngeal space: anatomic studies and surgical implications

“…The goal of surgery is complete removal of tumors with minimal morbidity. Many surgical routes to PPS have been described, from the classic surgical approaches (cervical, transparotid, cervical‐parotid with or without mandibulotomy, preauricular, and infratemporal fossa approaches) to the endoscope‐assisted transnasal/transoral/transvestibular corridors, and combinations of these approaches . Ferrari et al recently reported a complete spectrum of anatomic routes to PPS .…”