The clival line as an important anatomical landmark during endoscopic third ventriculostomy of the floor of the third ventricle

Background. The arachnoid membranes are widely and unevenly distributed in the cranial cavity and vary greatly in appearance and configuration. Understanding the distribution and configuration of intracranial arachnoid membranes is useful in order to make full use of natural anatomical landmarks during operations. Objective. The purpose of the study is to study the features of the endoscopic anatomy of the distribution and configuration of the arachnoid membranes of the base of the brain. Material and methods. The endoscopic and microsurgical anatomy of the arachnoid membranes of the brain base, the clival line, and the basal cisterns were studied on 20 cadaveric preparations with vessels pre-stained with colored silicone. Results. The basal attachment of the mesencephalic leaf of the Liliequist membrane and its caudal continuation in the form of a pre-pontine membrane on both sides of the basillar artery form a U-shaped thickening (clival line) on the outer arachnoid membrane, it serves as a reliable reference point for dissection of the surrounding arachnoid membranes during endoscopic third ventriculo-stomy (ETV). The proposed 4 types of perforation mechanisms, depending on the anatomical changes of the internal arachnoid membranes, make it possible to plan the ideal position of the stoma associated with the Liliequist membrane complex, which de-termines the long-term success of the operation. Conclusion. The U-shaped thickening (clival line) on the outer arachnoid membranes serves as a reliable reference point for dissection of the surrounding arachnoid membranes during ETV. © 2023, Media Sphera Publishing Group. All rights reserved.