2025 Proffered Presentations
S219: DEFINING LANDMARKS IN SKULL BASE SURGERY: A MORPHOMETRIC CADAVERIC STUDY OF THE INTERFALCIFORM LIGAMENT
Guilherme Mansur, MD1; Guilherme Finger, MD, MSc1; Dan Z Oberman2; Moataz D Abouammo, MD, MSc1; Chandrima Biswas, MD1; Mohammad B Alsavaf, MD1; Rodrigo Gehrke, MD1; Kyle C Wu, MD1; João Paulo Almeida, MD, PhD2; Daniel M Prevedello, MD1; 1The Ohio State University; 2Mayo Clinic Florida
Background: The advent of the endoscopic endonasal approach (EEA) revolutionized neurosurgery, particularly for skull base tumor treatment. This technique, leveraging the nostrils as natural corridors, facilitates direct access to the anterior skull base. Despite its efficacy, successful navigation of the EEA demands substantial training and intricate anatomical knowledge. Defining anatomical landmarks in the Skull Base to guide the surgeon through these approaches is paramount to optimize surgical strategies and mitigate risks. The interfalciform ligament sits underneath the limbus sphenoidale as a medial extension of the falciform ligament, on the roof of the optic canal in either side. It is a crucial, yet underexplored anatomical landmark in extended approaches over the sagittal plane. This study aims to elucidate the anatomical characteristics and surgical relevance of the interfalciform ligament through detailed cadaveric analysis.
Methods: A descriptive study was conducted on 30 cadaveric specimens at The Ohio State University Wexner Medical Center and the Mayo Clinic’s Skull Base Dissection Laboratory. Each specimen underwent endoscopic endonasal and transcranial dissections. Key measurements included the length and vertical distance of the interfalciform ligament, recorded via a high-resolution CT imaging system and surgical navigation software. Length was defined as the distance between the points where the ligament intersected the optic nerve on either side, while the vertical distance was measured as an imaginary perpendicular line extending from the midpoint of the superior intercavernous sinus to the interfalciform ligament. A quantitative analysis was performed, and normality was assessed using the Shapiro-Wilk test.
Results: The interfalciform ligament was identified in all specimens. The mean length was 12.85 mm (SD 1.54 mm), with values ranging from 10.10 mm to 16.10 mm. The mean vertical distance was 7.90 mm (SD 1.19 mm), ranging from 6.20 mm to 11.70 mm. Boxplots illustrated a consistent anatomical feature for both measurements. The Shapiro-Wilk test indicated that while the length measurements followed a normal distribution (p = 0.597), the vertical distance measurements did not (p = 0.033).
Conclusion: The interfalciform ligament is a consistent and reliable anatomical landmark in expanded endoscopic procedures such as the transtuberculum and transplanum approaches. We consider this landmark to be particularly valuable in cases where tumor-induced bone deformities or invasive lesions obscure normal anatomy. Revision surgeries can also distort expected anatomical features, necessitating the identification of reliable anatomical markers to guide the surgeon during the procedure. Understanding its dimensions and relationships enhances surgical navigation, minimizing the risk of injury to critical neurovascular structures. This study contributes to the foundational knowledge necessary for optimizing surgical outcomes and underscores the importance of precise anatomical landmarks in advanced neurosurgical approaches.
