Comparative Anatomic Skull Base Approaches to the Nasopharynx and Pharyngeal Aerodigestive Tract

Objective: The purpose of this study is to determine the extent of nasopharyngeal and pharyngeal access in progressive anterior skull base exposures.

Study Design: Anatomic, morphometric analysis of human cadaver heads.

Setting: Anatomy laboratory.

Participants: Latex injected adult cadaver heads.

Main Outcome Measures: Nasopharyngeal and pharyngeal mucosal surface area were measured with an endoscopic approach, a suprastructure maxillary swing (palate in native position), a complete maxillary swing with palatal split, and an anterior mandibular swing. Anatomic limits were also assessed for each approach.

Results: All four approaches could be completed in several heads bilaterally, surface area averages and limits are listed below. The endoscopic approach resulted in an average pharyngeal mucosal exposure of 243 mm², the superior swing approach resulted in an average of 158 mm² mucosal exposure, the complete maxillary swing approach resulted in an average of 366 mm² mucosal exposure, and the mandibulotomy approach resulted in an average pharyngeal mucosa exposure of 3,213 mm². When the soft palate was moved to expose more mucosa in the complete maxillary swing, an average exposure of 466 mm² was achieved. Anatomic limits for the endoscopic approach noted to be the palate, sphenoid, orbital floor superiorly and the nasal floor and lacrimal crest laterally. The superior swing limits were worse in all measured areas compared with the endoscopic visualization. Anatomic limits to complete maxillary swing include the soft palate and tongue limit, the mandible laterally and inferior orbital periosteum. Anatomic limits to the mandibulotomy include posterior and inferior oral cavity and prevertebral space.

Conclusion: When the nasopharynx contains pathology that requires surgical intervention, the surgeon may choose an endoscopic minimally invasive approach or several various open procedures depending on the inferior extent of the tumor into the aerodigestive tract. It is usually thought that open approaches offer better surgical access; however, our results support the endoscopic endonasal approach offering better nasopharyngeal mucosal exposure than a more invasive superior maxillary swing. The best mucosal exposure was accomplished with the complete maxillary swing and mandibulotomy; however, the extent of morbidity when entering into the oral cavity cannot be under estimated. These most invasive skull base access procedures allow the best access to tumors that involve pharyngeal airway below the level of the palate. Future advances in combined transoral and transnasal approaches may also allow surgeons to access these areas without open approaches. When choosing between endoscopic, superior maxillary swing, and complete maxillary swing, the surgeon can consider mucosal area exposure and anatomic limits to each approach.