2026 Proffered Presentations
S105: TRANSORAL ENDOSCOPIC ANATOMY OF THE PARAPHARYNGEAL INTERNAL CAROTID ARTERY: A CADAVERIC STUDY WITH NOVEL MODULAR CLASSIFICATION
Gianluca L Fabozzi1; Rakhmon Egamberdiev1; Thibault Passeri1; Maria Karampouga1; Longgang Yu1; Eric W Wang2; Garret Choby2; Georgios A Zenonos1; Paul A Gardner1; Carl H Snyderman2; 1Department of Neurological Surgery, University of Pittsburgh Medical School (UPMC), Pittsburgh, Pennsylvania; 2Department of Otolaryngology, University of Pittsburgh Medical School (UPMC), Pittsburgh, Pennsylvania
Objective: The parapharyngeal internal carotid artery (ppICA) lacks a solid and uniform classification, and the absence of consistent terminology hinders anatomical reporting and surgical planning. To address this gap, we introduce a novel modular classification of the ppICA into three surgical segments, aligned with the topographic subdivision of the parapharyngeal space (PPS): infrapetrous or upper ppICA (UppICA), extending from its entry into the carotid canal to the stylo-muscular complex; stylo-muscular or middle ppICA (MppICA), located at the level of the styloid tip in relation to the stylopharyngeal diaphragm and ligamentous complex; and infra-styloid or lower ppICA (LppICA), extending from this intersection to the most caudal point accessible through a transoral route (Fig.1). This framework was then applied to quantitatively assess angle of exposure and surgical freedom for each segment during a transoral endoscopic approach.
Methods: Ten sides from five latex-injected cadaveric heads were dissected using a rigid endoscopic-assisted transoral corridor via a retromolar trigone incision. Image-guided neuronavigation (accuracy <1 mm) was used for accurate measurements. Surgical freedom was evaluated with 25-cm instruments placed at three predetermined targets: the carotid canal (CC) for UppICA, the styloid tip intersection for MppICA, and the lowest transorally accessible point for LppICA. Instruments were moved through four extreme trajectories (cranial, caudal, medial, lateral) to define the manoeuvring area (Fig.2). Angles of exposure were calculated in sagittal and coronal planes, with the distal instrument tip fixed at each target and the proximal shaft displaced to maximal excursions.
Results: Surgical freedom varied across segments, being 84.62 cm² at MppICA, 53.07 cm² at LppICA and 43.53 cm² at UppICA (Fig. 3 and 4). MppICA offered the largest manoeuvring area (+94% vs UppICA; +59% vs LppICA). MppICA also offered the most favorable angulation (mean sagittal/coronal 30.1°/32.5°) (Fig. 4) compared with LppICA (21.4°/27.9°) and UppICA (21.8°/24.0°). A composite index of accessibility (area × mean angle) confirmed a distinct gradient of transoral exposure, with MppICA being the most accessible, followed by LppICA and UppICA.
Conclusion: The PPS is among the most anatomically complex regions, owing to its depth and dense neurovascular contents, and inadvertent ppICA injury remains one of the most feared complications. The proposed modular classification provides a reproducible anatomical framework that enables segment-specific quantification of surgical working space and enhances consistency in describing the transoral surgical corridor. MppICA emerges as the segment with the greatest manoeuvring area and the broadest bidirectional angles. The LppICA offers conditional access with sagittal constraints, while the UppICA remains the most restricted, underscoring the potential need for adjunctive corridors. This cadaveric study proposes a standardized anatomical roadmap of the ppICA. An ongoing investigation will refine key segmental landmarks and morphometric data, while future comparative studies with alternative surgical routes and clinical validation will be essential, particularly to address tumor-related anatomical distortion and the risks of intraoperative bleeding.
