Minimizing Septectomy for Endoscopic Transphenoidal Approaches to the Sellar and Suprasellar Regions: A Cadaveric Morphometric Study

Objective: As experience in minimal access endoscopic surgery to sellar and suprasellar pathology increases, efforts to minimize resection of normal sinonasal anatomy can provide means to decrease sinonasal morbidity, as well as decrease operative times. In this cadaveric study, we evaluate the minimal septectomy that provides exposure to sellar and parasellar regions in binaral, endoscopic transphenoidal surgery

Design: Dissections were performed on 10 formalin-fixed, navigation software registered cadaver heads. Quantitative measurements of exposure were obtained for the posterior sphenoid sinus wall, the angle of exposure based at the inferior border of the piriform aperture, and the distance between the lateral optico-carotid recesses (OCRs). All measurements were calculated using frameless stereotaxis software and a 15cm stereotactic wand. Dissections started with wide bilateral sphenoidotomies including an initial 5mm posterior septectomy and lateralization of the middle turbinates. The maximum width of the posterior sphenoid sinus wall at the level of the sellar floor and inter-OCR distance was measured. Posterior septectomies were made incrementally at 5mm intervals to 35mm; the horizontal width and angle of exposure were measured in each interval. Horizontal exposure following bilateral turbinectomies in each specimen was also measured.

Results: The mean width of the posterior sphenoid sinus was 29.4 ± 3.7mm. The mean inter-OCR distance was 26.4 ± 4.8mm. With a 5mm septectomy, the width of exposure of the posterior sphenoid sinus was 21.1 ± 2.8mm. This width of exposure increased progressively until a 20 mm posterior septectomy was achieved. No significant increments in mean horizontal exposure (p = 0.96) and angle (p = 0.70) were gained with a posterior septectomy greater than 20mm. Comparing maximum posterior sphenoid sinus wall exposure, addition of bilateral middle turbinectomies did not add significant horizontal exposure of the posterior sphenoid sinus wall (p = 0.90). Bilateral OCRs were reached with 20mm posterior septectomy and beyond.

Conclusion: This cadaveric study demonstrates that a posterior septectomy greater than 20mm does not increase access to the posterior sphenoid sinus wall. For most sellar and suprasellar pathologies, bilateral access to the OCRs is typically sufficient and can be achieved with a posterior septectomy of 20mm utilizing straight instruments. The addition of bilateral middle turbinectomies does not significantly increase the exposure, demonstrating that preservation of these structures is favored. Although not evaluated in this study due to significant variables, the use of angled instruments and angled endoscopes may allow more exposure with a smaller septectomy.