Endoscopic anatomical study of the arachnoid architecture on the base of the skull. Part I: The anterior and middle cranial fossa

Abstract

Minimally invasive neurosurgery requires a detailed knowledge of microstructures, such as the arachnoid membranes. In spite of many articles addressing arachnoid membranes, its detailed organization is still not well described. The aim of this study is to investigate the topography of the arachnoid in the anterior cranial fossa and the middle cranial fossa. Rigid endoscopes were introduced through defined keyhole craniotomies, to explore the arachnoid structures in 110 fresh human cadavers. We describe the topography and relationship to neurovascular structures and suggest an intuitive terminology of the arachnoid. We demonstrate an “arachnoid membrane system”, which consists of the outer arachnoid and 23 inner arachnoid membranes in the anterior fossa and the middle fossa. The inner membranes are arranged in two “arachnoid membrane groups” in the examined regions. The first is the carotid membrane group, located in the suprasellar region, consisting of seven paired and three unpaired inner membranes and the outer arachnoid on its base. The second is the Sylvian membrane group, composed of three inner membranes of the Sylvian fissure and completed by the outer arachnoid. Our findings should be very helpful in understanding the complex organization of the cranial arachnoid, which is mandatory for the safe and effective use of minimally invasive endoscopic techniques.