Definition of the Anterior Wall of Cavernous Sinus: A Correlation between Transcranial and Endonasal Endoscopic Perspectives

Introduction: The cavernous sinus (CS) was traditionally described as a boat with a narrow keel that consists of four walls: lateral, medial, posterior, and superior or roof. The medial wall included two portions, sellar and sphenoidal, which are interrupted by the inter-cavernous sinus and quite different in anatomical and histological origin. The definition is confusing from an endonasal approach perspective and the sphenoid portion was intuitively called the anterior wall of CS by several authors. Here we propose a definition of the anterior wall of the CS and correlate anatomical landmarks between transcranial and endoscopic perspectives.

Materials and Methods: Five anatomical specimens with neurovascular latex injection were used for microscopic and endoscopic dissection. Anatomical landmarks were noted, compared, and described.

Results: The anterior wall of the CS can be reliably defined/identified from transcranial and endoscopic perspectives with the following landmarks: optic strut, proximal dural ring, middle clinoid, lateral ridge of sellar floor, petrous process of the sphenoid, lingual process, and maxillary strut. A dural thickening connecting the lateral optic strut and lingual process was found in all specimens from both perspectives, which correlates with the lateral border of the carotid sulcus on the sphenoid bone. We propose the name opticolingual dural fold for the structure, which effectively divides the anterior wall into two portions, medial half consisting of the carotid sulcus and lateral half consisting of middle fossa dura. From an endoscopic perspective, the medial portion correlates with the ICA and inferior compartment of the CS, and the lateral portion correlates with the abducens nerve and lateral compartment of the CS.

Conclusion: We propose the definition of the anterior wall of the CS with reliable bony landmarks that can be readily and consistently identified from both transcranial and endoscopic perspectives. Hopefully, this common definition will promote accurate and convenient communication regarding the CS and better orientation during endonasal endoscopic surgery as well as clear correlation with open approaches.