Radiological Study of the Ethmoid Preservation during the Endoscopic Superior Ethmoidal Approach Compared with the Traditional Endoscopic Anterior Cranial Base Approach to Intracranial Pathologies

Background Patients who undergo surgery for purely intracranial pathologies, such as olfactory groove meningiomas, via an endoscopic endonasal approach have significantly increased postoperative nasal volumes. In these cases, usually the only remaining structures are the anterior septum and inferior turbinates. Excessive removal of nasal structures such as the middle turbinates and the ostiomeatal complex result in permanent changes in airflow dynamics, and therefore, predispose the patient to postoperative crusting and the need for debridement. In contrast, the superior ethmoidal approach maximizes the preservation of critical nasal structures while still allowing enough space to sufficiently access the anterior cranial base. This approach creates a more physiologic airflow by preserving the middle turbinates, uncinate process, and bulla ethmoidalis, subsequently decreasing nasal morbidity. In this article, we quantify the amount of ethmoid bone preserved by utilizing the superior ethmoidal approach instead of the traditional approach in cases of olfactory groove meningioma.

Methods Six patients with olfactory groove meningioma underwent endoscopic endonasal approaches for tumor resection. In three patients, we performed the traditional anterior cranial base approach, while in the other three patients, we performed the superior ethmoidal approach. Preoperative MRI scans were used to measure the area of ethmoid bone at two separate slice locations. Postoperative scans were used to determine the resected area at both slice locations as part of the surgical approach. The difference between preoperative and postoperative measurements was calculated to quantify the amount of preserved ethmoid.

Results In the three patients receiving the superior ethmoidal approach, there was satisfactory visualization of the meningioma at the anterior cranial base with bilateral preservation of the middle meatus, uncinate process, and bulla ethmoidalis. The tumor was completely resected in these three cases. Compared with the traditional approach, the superior ethmoidal approach resulted in greater preservation of sinonasal structures, with 52.7% of ethmoid preservation (average residual area of 3.67 cm²) in the plane of the greatest orbital dimension, and 65.2% of ethmoid preservation (5.45 cm²) in the plane of the anterior sphenoid wall.

Conclusion The endoscopic superior ethmoidal approach for purely intracranial pathologies minimizes the unnecessary resection of crucial physiologic structures within the nasal cavity, such as the middle turbinates and components of the ostiomeatal complex, while still allowing sufficient access to the anterior cranial base. The ethmoid seems to be better preserved posteriorly compared with anteriorly during this approach.

 

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