Classification of Sphenoid Sinus Pneumatization: Relevance for Endoscopic Skull Base Surgery

TLDR

The study proposes a classification of sphenoid sinus pneumatization in the coronal plane to guide preoperative planning for endoscopic endonasal surgery. An observational anatomical study of 204 hemisinus CT scans measured pneumatization geometry and its relationship to the foramen rotundum and vidian canal, forming the basis of the classification. The classification, with three types accounting for 25%, 39%, and 37% of cases, predicts the distance between the vidian and maxillary nerves, determines the surgical window size, and highlights neurovascular risks. Level of Evidence 4, Laryngoscope 125:577–581 (2015).

Abstract

Objectives/Hypothesis The goal of this study was to present a classification based on the degree of pneumatization of the sphenoid sinus in the coronal plane that can be used to instruct preoperative planning for endoscopic endonasal surgery (EES). Study Design Observational anatomical study. Methods The geometry of sphenoid sinus pneumatization was characterized (n = 204 hemisinus) on high-resolution computed tomography scans, and its associations with the location of the foramen rotundum (FR) and the vidian canal (VC) were measured. Based on these findings, we propose a simple classification of pneumatization of the sphenoid sinus relevant for EES. Results The lateral recess of the sphenoid sinus was pneumatized lateral to the FR in the coronal plane in 54% of patients. The distance separating the FR and the VC correlated strongly with the depth of the lateral recess. Based on these findings, we propose three types of pneumatization: type I, where the pneumatization extends from the midline to the medial edge of the VC (25%); type II, where the pneumatization reaches the medial edge of the FR (39%); and type III, where the pneumatization extends beyond the medial border of the FR (37%). Conclusions The proposed sphenoid sinus pneumatization classification in the coronal plane is simple and reproducible. It predicts the distance between vidian and maxillary nerve, determines the size of the surgical window to access the middle cranial fossa transnasally, and instructs on the potential risk to neurovascular structures during surgery. Level of Evidence 4 Laryngoscope, 125:577–581, 2015