Comparison of the Impact on Simulated Airflow and Heat Transport between the Superior Ethmoidal Approach for Endoscopic Endonasal Anterior Cranial Base Resection and the Traditional Endoscopic Anterior Cranial Base Approach

Background: The traditional endoscopic endonasal anterior cranial base approach (TA) involves total removal of intranasal structures. The endoscopic endonasal superior ethmoidal approach (SEA) is a more conservative technique to access the anterior cranial base with preservation of middle turbinates, osteomeatal complex, part of the ethmoid cells, and most of the septum (Fig. 1). It has been designed as an alternative method to resect anterior cranial base lesions that have minimal or no extension intranasally. Previous studies have noted altered nasal airflow and heat transport following TA. The severity of postoperative changes in airflow and mucosal wall interactions may correlate with the amount of nasal tissue removed.

Objective: This study aims to compare the impact on simulated airflow and heat transport between TA and SEA using computational fluid dynamics.

Methods: Nine patients were included in the study: three control patients with normal sinus anatomy and no intracranial pathology, and six patients with intracranial pathology: three patients who underwent SEA and three patients who underwent TA. Computed tomographies (CT) from control patients and postoperative CT of SEA and TA patients were studied. Three-dimensional sinonasal models were constructed from CT scans, and hybrid computational meshes were created from these models. Nasal Advanced Systems of Airflow Laboratory (NASAL) was used to analyze changes in airflow, temperature, pressure distribution, and wall shear stress in coronal equidistant slices of the CT images. Nasal cavity volume calculations were completed using Osirix MD.

Results: In the SEA group, nasal preservation did not limit tumor resection as complete resection was achieved in all cases despite large tumor sizes (mean tumor size 3.4 × 3.0 × 1.8 cm). Comparing patient controls with the SEA group, total nasal cavity volume did not change significantly after SEA approach (p = 0.91), and the average flow rate increased 1.37 l/min (p = 0.25). The average nasal cavity temperature did not change significantly (p = 0.23), reaching a maximum of 36.5°C in the nasopharynx. Average wall shear stress (WSS) increased by 0.01 Pa in the SEA group (p = 0.12). Comparing patient controls with the TA group, total nasal cavity volume increased significantly after TA approach (p = 0.03), and the average flow rate increased 7.20 L/min (p = 0.03; Fig. 2). The average nasal cavity temperature reduced 3.47°C (p = 0.02). Average WSS increased by 0.02 Pa (p = 0.08). In both groups, average airflow velocity peaked at 1.0 to 2.0 cm from the nostril, corresponding to the area of surgical resection. Furthermore, changes in average velocity throughout the nasal cavity correlated with changes in average WSS.

Conclusion: The TA demonstrated significant increase in nasal cavity volume and average flow rate and reduced nasal cavity temperatures, whereas the SEA did not result in significant changes in these parameters when compared with patient controls. The SEA preserves not only the majority of anatomical structures of the nasal cavity in the anterior cranial base resection, but also maintains the physiologic airflow and heat transport mechanisms postoperatively. Due to the impact in nasal physiology, SEA is indicated in patients with anterior cranial base pathology with minimal or no intranasal involvement.

No conflict of interest has been declared by the author(s).