The morphology of the human cavernous sinus

Abstract

The cavernous sinus (CS) is a large intracranial venous plexus located on either side of the sphenoid bone and closely associated with four cranial nerves, the internal carotid artery (ICA) and the pituitary gland. However, descriptions of the morphology of the CS within the literature are inconsistent. The aim of this study was to investigate four inconsistencies relating to CS morphology: (1) CS venous architecture; (2) the relationship of the CS to the pituitary venous drainage; (3) the morphology of the ICA within the CS; and (4) the consistency of the path of the ICA and cranial nerves through the CS. Five bilateral cadaver CS specimens (four male, 65-93 years) were decalcified, and embedded in paraffin wax and serially sectioned. A further five bilateral specimens (three male, 66-85 years) were embedded in methylmethacrylate resin and serially sectioned. High resolution macro- and microscopic images of the serial sections were photographed and analysed. Micro computed tomography was used to compare the sphenoid bone morphology. The CS was shown to be a dural venous sinus that was irregularly compartmentalised by the ICA and connective and adipose tissue. In general four venous compartments were recognised (lateral, medial, superior, and inferior) together with the four intercavernous sinuses (anterior, posterior inferior and superior). The adipose tissue within the CS contained small veins that interconnected adjacent CS compartments. Sphenoid bone morphology was variable between specimens, as demonstrated by the highly inconsistent interclinoid distances. Peripheral hypophysial veins were identified exiting through the pituitary capsule of the central portion of the anterior lobe and the pituitary cleft draining into the CS and intercavernous sinuses. The course of the ICA and cranial nerves proved to be variable in relation to the vertical height of the lateral CS wall at two standardised positions. The morphology of the ICA within the CS was unable to be analysed due to inadequate specimen quality. The CS is a compartmentalised dural venous sinus and has with extensive venous connections with the pituitary gland. The morphology of the human CS varies both in relation to sphenoid bone morphology and the location and paths of intracavernous structures. These variations may have potential clinical significance in relation to hypophysectomy and functional implications in our understanding of this unique anatomical arrangement.