The Viet Tran; Quang Tuyen Le & Huyen Tran Lam

The parapharyngeal space (PPS) is a deep cervical space whose intimate relationship with the internal carotid artery (ICA) and lower cranial nerves makes surgery within it technically demanding. The endoscopic transoral approach (ETA) offers a minimally invasive alternative to classical open routes; however, systematic quantitative descriptions of the inside-out anatomy visible through this corridor remain scarce. The objective of this study was twofold: (1) to describe the layered anatomy of the PPS as encountered during endoscopic transoral dissection in fresh cadaveric specimens, with measurement of ICA distances from two clinically relevant landmarks; and (2) to validate the translational applicability of these cadaveric findings through a single clinical case. Endoscopic transoral dissection was performed on 10 fresh adult cadaveric specimens (20 sides) using rigid 0° and 30° endoscopes following carotid injection with colored contrast. Two bilateral measurements were recorded with 1-mm precision: pterygoid hamulus-to-ICA (PTH-ICA) and pharyngeal mucosa-to-ICA (Mucosa-ICA) distances. One patient with a prestyloid PPS tumor meeting cadaveric-defined anatomical criteria subsequently underwent ETA. Stepwise dissection consistently identified the pharyngeal mucosa, superior pharyngeal constrictor, prestyloid fat compartment, styloglossus and stylopharyngeus muscles, styloid diaphragm, and stylohyoid ligament before reaching the ICA. Mean PTH-ICA distance was 26.36 ± 2.94 mm (left) and 27.15 ± 5.11 mm (right); mean Mucosa-ICA was 22.85 ± 2.79 mm (left) and 23.04 ± 2.42 mm (right). No significant left-right asymmetry was detected (p > 0.05). In the clinical case, operative time was 45 min, blood loss < 50 mL, with no intraoperative complications; histopathology confirmed pleomorphic adenoma with no recurrence at six months. The cadaveric study defines a reproducible layered anatomical corridor for ETA, with the pterygoid hamulus and stylopharyngeus muscle as key safety landmarks. The clinical case confirms direct translation of cadaveric findings to operative practice, supporting the safety and feasibility of ETA for small-to-medium benign prestyloid PPS tumors.

KEY WORDS: Parapharyngeal space; Endoscopic transoral approach; Surgical anatomy; Cadaveric study; Pleomorphic adenoma.

TRAN, T. V.; LE, Q. T. & LAM, H. T. Endoscopic transoral approach to the parapharyngeal space: A cadaveric anatomical study with single clinical case validation. Int. J. Morphol., 44(4):1500-1508, 2026.