Object : the dura mater is made of two layers: the endosteal layer (outer layer), which is firmly attached to the bone and the meningeal layer (inner layer), which directly covers the brain and spinal cord. These two dural layers join together in most parts of the skull base and cranial convexity, and separate into the orbital and perisellar compartments or into the spinal epidural space to form the Extra Dural Neural Axis Compartment (EDNAC). The EDNAC contains fat and/or venous blood. The aim of this dissection study was to anatomically verify the concept of the EDNAC by focusing on the dural layers surrounding the jugular foramen area.
Methods : we injected ten cadaveric heads (20 jugular foramens) with colorated latex and fixed them in formalin. The brainstem and cerebellum of seven specimens were cautiously removed in order to allow a superior approach to the jugular foramen. Special attention was paid to the meningeal architecture of the jugular foramen, the petrosal inferior sinus and its venous confluence to the sigmoid sinus, the glossoparyngeal, vagus and accessory nerves. The three remaining heads, were bleached with a 20% hydrogen peroxide solution. This procedure produced softening of the bone without modifying the fixed soft tissues, thus permitting coronal and axial dissections.
Results : the EDNAC of the jugular foramen was limited by the endosteal and meningeal layers and contained venous blood. These two dural layers joined together at the level of the petrous and occipital bones and separated themselves at the inferior petrosal sinus, the sigmoid sinus and around the lower cranial nerves to form the EDNAC. Our study of the dural sheaths allowed us to describe an original compartmentalization of the jugular foramen in 3 parts: two neural compartments – glossopharyngeal and vagal – and the interperiosteodural compartment.
Conclusions. In this dissection study, the existence of the EDNAC concept in the jugular foramen was demonstrated, leading to the proposal of a novel three parts compartmentalization challenging the classical two parts compartmentalization of the jugular foramen.