Utility of a Nasal Access Guide in Endoscopic Endonasal Skull Base Surgery: Assessment of Use during Cadaveric Dissection Course

Background: A nasal access guide for endoscopic endonasal approaches (EEA) to the skull base has been recently developed and is approved for clinical use. The device is a nonabrasive, pliable stent that is placed in the bilateral nares. It seats at the nasal vestibule and provides a working corridor to the posterior nasal cavity. It was designed to minimize mucosal trauma, reduce instances of inadequate visualization caused by endoscope lens obscuration, and lessen the run-in of blood into the surgical field. While the device is currently being used at institutions in the United States, its utility has yet to be formally investigated.

Objectives: To assess the utility of a nasal access guide on endoscopic visualization during EEA that involve dissection and drilling posterior to the sphenoid rostrum during a cadaveric dissection course.

Methods: Course participants in a cadaveric endoscopic endonasal skull base course were observed during the transsellar or transclival hands-on dissection portions of the course. Dissection stations, consisting of one surgeon or a two-surgeon team and one cadaver head, were observed for 5 minutes with the nasal access guide in place and 5 minutes without it during the same portion of the procedure. Observation did not commence until completion of bilateral sphenoidotomies and posterior septectomy. For both conditions (with and without the nasal access guide), reviewers tabulated the number of instances the endoscope was withdrawn for lens cleaning and when there was inadequate visualization on the monitor due to soiling of the endoscope lens. Following the procedure, participants completed a Likert-scale survey examining nine dimensions of the nasal access guide’s utility and provided an overall grading of the device’s utility. Each dimension was rated as such: “excellent” (3 points), “acceptable” (2 points), or “suboptimal” (1 point); for a maximum of 27 total points. The overall grading was assessed with the same scale. Additionally, predissection computed tomography (CT) findings (presence of Onodi cells, concha bullosa, caudal septum deviation, narrow nasal vestibule, and sellar configuration type) of the cadaver heads was correlated with survey and observation findings.

Results: Twenty-four dissection stations were observed. The study group was composed of 15 otolaryngologists (1 resident, 4 fellows, 9 attendings; 1 did not indicate experience level) and 21 neurosurgeons (5 residents, 2 fellows, and 12 attendings; 2 did not indicate experience level). The mean instances of soiling of the endoscope lens was significantly reduced by 32.3% with the nasal access guide (3.75 vs. 2.54; p <  0.001). The mean instances of manual endoscope lens cleaning was reduced by 57.5% (1.67 vs. 0.71; p = 0.113). These findings were not significantly affected by any CT findings. The mean survey score was 22.89 (standard deviation of 2.76). Scores were not significantly affected by specialty or experience level. The mean overall grading was 2.65 (mode of 3 [“excellent”]).

Conclusion: Nasal access guides can significantly reduce instances of inadequate visualization during EEA to the skull base. Participants who trialed the device rated different facets of its utility favorably and most often, assessed its overall utility as being “excellent.”