Surgical anatomy and landmarks of the styloglossus muscle identified through transoral endoscopic dissection of the parapharyngeal space

Purpose Transoral endoscopic surgery of the parapharyngeal space (PPS) reduces morbidity compared with external approaches, but the narrow surgical corridor, the “inside-out” viewing angle, and the lack of visible bony landmarks increase the risk of hemorrhage, airway compromise, and cranial nerve injury. This study aimed to describe the endoscopic identification of the styloglossus muscle (SGM) via the transoral route, to evaluate its relationship with high-risk structures (external carotid artery, lingual nerve), and to propose an SGM-based orientation protocol for transoral endoscopic PPS surgery. Methods A descriptive cadaveric anatomical study was performed on 10 fresh adult cadaveric heads (20 sides). Transoral endoscopic dissection of the PPS was carried out layer by layer, from the mucosa through the superior pharyngeal constrictor muscle to the prestyloid fat pad. Distances from the SGM to the lateral pharyngeal mucosa, to the lingual nerve at two anatomical levels, and to the external carotid artery were measured and expressed as mean ± SD and range (minimum–maximum). Results The SGM was identified in 100% of dissected specimens as a muscular bundle coursing obliquely from the styloid region anteromedially toward the tongue base, deep to the lateral pharyngeal wall, and became visible early after dissection of the prestyloid fat pad. The external carotid artery and its branches (lingual and facial arteries) coursed posterior to the SGM, while the lingual nerve ran superolateral to it and approached it more closely toward the tongue base. Conclusion Within this cadaveric cohort, the SGM was a readily identifiable and consistent anatomical landmark under transoral endoscopy that may provide orientation during PPS access, particularly for recognizing the posterior limit of the prestyloid compartment before entering the vascular-rich poststyloid region. Its value as a surgical safety landmark requires confirmation in clinical studies.