Transoral anatomy of the tonsillar fossa and lateral pharyngeal wall: anatomic dissection with radiographic and clinical correlation.

OBJECTIVES/HYPOTHESIS To evaluate the transoral anatomy of the tonsillar fossa and lateral pharyngeal wall and to correlate these findings with radiographic measurements and transoral robotic surgery (TORS) of patients with early tonsillar tumor. STUDY DESIGN Preclinical cadaveric study and patient cohort. METHODS Six complete cadaveric dissections were performed to identify key anatomic landmarks, and these landmarks were validated in two consecutive patients with T1 human papillomavirus-positive squamous cell carcinoma of the tonsil treated by TORS. For radiographic landmark analysis, 25 patients who underwent contrast-enhanced computed tomography (CT) of the neck for a variety of endoscopic skull base procedures were selected. Measurements were taken from the lateral pharyngeal wall at C2-C3 interspace and greater horn of hyoid (C6) to the external carotid artery (ECA). RESULTS The glossopharyngeal (IX) nerve was consistently identified deep to the superior constrictor musculature and at the intersection of the posterior tonsillar pillar with the base of tongue. The styloglossus muscle forms the deep plane medial to the ECA. The mean measurements for left C2-C3 interspace to the ECA and right C2-C3 interspace to ECA were 17.6 ± 0.8 mm and 18.4 ± 0.8 mm, respectively. Similarly, the mean measurements for left hyoid to ECA and right hyoid to ECA were 3.4 ± 0.8 mm and 4.3 ± 0.6 mm, respectively. CONCLUSIONS A systematic approach to dissect the tonsillar fossa and lateral pharyngeal wall can be performed using key anatomic landmarks. CT measurements taken at the C2-C3 interspace and greater horn of hyoid bone (C6 level) to the ECA are consistently and reliably achieved.