Endoscopic Windows for Increased Visualization in Endoscopic Skull Base Surgery

Objectives: To quantify progressive nasopharyngeal and posterior maxillary wall exposure using a zero-degree endoscope through the addition of posterior septal window and Denker’s procedure in endoscopic skull base surgery.

Design: Anatomic cadaver study.

Setting: Anatomy laboratory.

Participants: Six dissections in latex injected human cadaver specimens.

Main Outcome Measures: Nasopharyngeal and maxillary sinus mucosal exposure were quantified with measurements made with a 0-degree endoscope from the head of both the inferior (IT) and middle turbinates (MT) with and without a posterior septal window or anterior “Denker’s” maxillary window.

Results: The average exposure of nasopharyngeal mucosa using a 0-degree endoscope was 2.1 ± 1.0 cm² from the IT and 2.8 ± 1.0 cm² from the MT. The creation of an ~1 cm × 2 cm posterior septal window led to a statistically significant increase in nasopharyngeal exposure to 4.9 ± 2.3 cm² from the IT and 8.9 ± 4.7 cm² from the MT (two-tailed t-test, p < 0.05). After creation of a medial Denker’s maxillectomy, the extent of lateral exposure of the posterior maxillary sinus was measured from the medial maxillary sinus wall using a 0-degree endoscope and found to be 1.3 ± 0.2 cm at the IT and 2.2 ± 0.4cm at the MT. Addition of Denker’s procedure resulted in a significant increase in lateral exposure to 3.3 ± 0.6 cm and 4.1 ± 0.1 at the IT and MT, respectively (two-tailed t-test, p < 0.05).

Conclusions: The posterior septal window results in a significant increase in area of nasopharyngeal exposure, and Denker’s procedure a significant increase in lateral exposure of the posterior maxillary wall in skull base surgery with a 0-degree endoscope. When working with a two-surgeon four-handed technique, 0-degree visualization gives the team the most direct operating corridor, and the majority of our instruments are best designed for 0-degree exposures. These endoscopic “windows” provide important tools to the endoscopic skull base surgeon for maximizing targeted exposure to the skull base while minimizing surgical morbidity.