Revisiting the Structure of the Cavernous Sinus Walls: An Anatomical Study of the Dural Layers

Objectives: The anatomy of the cavernous sinus (CS) has been described by many authors. However, the literature remains confusing, and without consensus on CS' detailed dural architecture. The objective of this study was to integrate previous knowledge about CS anatomy, review several anatomic hypotheses of CS walls, and create a comprehensive concept of the structure of CS walls using cadaveric dissections.

Materials and Methods: Bilateral stepwise dissections of CS on 15 cadavers (30 sides) were performed. Five specimens were dissected from lateral approaches, five specimens were cut in the axial plane to study the superior wall, and five were dissected via endoscopic endonasal approach to study the medial wall.

Results: Based on histologic and embryologic data, we developed several anatomic concepts and investigated them through dissections: (1) bones of a skull are covered by periosteum both on the exocranial and endocranial surfaces without any interruption between them. Endocranial periosteum is an outer layer of dura mater (periosteal dural layer [PDL]; [Fig. 1]); (2) all neuraxis structures are covered by a meningeal layer (MDL) of dura ([Fig. 1]); (3) cranial nerves (CNs) that originate from the posterior cranial fossa (PCF) and course through CS are ensheated by one layer of MDL from the PCF. The exception of this concept is CN VI ([Fig. 2]); (4) at the sites of skull base foramina, all dural layers fuse together ([Fig. 3]). Thus, the medial wall of CS is formed by PDL at the level of the paraclival ICA and by MDL at the level of pituitary gland. Anterior and inferior walls of CS are formed by single layer of PDL. The lateral wall of CS consists of (1) MDL of mesial temporal lobe, (2) a portion of PDL that splits in two at the point of foramen rotundum (one layer courses superiorly from the upper margin of V2 and becomes PDL of the lateral CS wall, and the other goes medially and becomes the floor of CS), and (3) a meningeal layer of CNs III, IV, and V1 from the PCF. The latter two layers (2 and 3) are tightly fused together, which led to the hypothesis of CNs being embedded into the so-called “reticular” layer of the lateral wall of CS. However, these two layers can be separated from each other and follow the principle no. 3. The posterior wall of CS is an “inferomedial triangle” which is formed by a MDL of PCF dura and the posterior petro-clinoidal and Gruber's ligaments, derivatives of the PDL. The roof of CS is composed of two parts: the posterior part of the clinoidal triangle (PDL) and oculomotor triangle (MDL and PDL; [Fig. 4]).

Conclusion: The concept of CS walls structure lies through the study of the distribution of the dural layers inside the cranial cavity. Combinations of two dural layers (periosteal and meningeal) build boundaries of CS. Single layer dura is found on the medial, anterior and inferior walls, double layer on the posterior and part of the superior wall, with a triple layer on the lateral wall of CS ([Fig. 4]).

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

Publication History

Article published online:
12 February 2021