Microsurgical Anatomy of the Inferomedial Paraclival Triangle: Contents, Topographical Relationships and Anatomical Variations

Abstract

The inferomedial triangle is one of the two surgical triangles in the paraclival subregion of the skull base. It is delineated by the posterior clinoid process, the dural entrance of the trochlear nerve and the dural entrance of the abducens nerve. The aim of the present article is to describe the anatomical variations within the inferomedial triangle. Measurements of the triangle’s borders and area were supplemented by detailed observations of the topographical anatomy and various arrangements of its contents. Nine adult cadaveric heads (18 sides) and 28 sagittal head sections were studied. The mean area of the inferomedial triangle was estimated to be 60.7 mm2. The mean lengths of its medial, lateral and superior borders were 16.1 mm, 11.9 mm and 10.4 mm, respectively. The dorsal meningeal artery was identified within the inferomedial triangle in 37 out of 46 sides (80.4%). A well-developed petrosphenoidal ligament of Grüber was identified within the triangle on 36 sides (78.3%). Although some structures were variable, the constant contents of the inferomedial triangle were the posterior petroclinoid dural fold, the upper end of the petroclival suture, the gulfar segment of the abducens nerve and the posterior genu of the intracavernous internal carotid artery.

Gross and Micro-Anatomical Study of the Cavernous Segment of the Abducens Nerve and Its Relationships to Internal Carotid Plexus: Application to Skull Base Surgery

“…Newman [41] concludes that CS surgery results in transient worsening of cranial nerves III-VI function. Consequently, the ability to conduct successful surgeries within this area is based mainly on an improved understanding of the anatomy and pathology in the parasellar and petroclival regions combined with modern neuroimaging [10,14,42,43].…”

The petroclinoid ligament: a meta-analysis of its morphometry and prevalence of mineralization with a review of the literature

“…Furthermore, it is crucial to understand that the PCL and posterior petroclinoid fold are two independent structures. The petroclinoid fold is a fold of the dura mater that extends between the anterior and posterior clinoid processes and the petrosal part of the temporal bone, and should not be referred to as a ligament [34]. Based on the results of the present meta-analysis, the PCL should be referred to as the petroclinoid ligament, because it represents this structure in the most precise way.…”

Microanatomical study of arachnoid granulations and meningeal architecture around Meckel’s cave

“…Summarizing the information from the present study, clusters of arachnoid granulations of different sizes occupied variable positions along the trigeminal ganglion around the origins of the ophthalmic, mandibular, and maxillary divisions of the trigeminal nerve. This study also paid attention to the relation of arachnoid granulations to selected surgical triangles, which has not been discussed in the literature before [ 14 , 22 , 37 ]. Histological examination revealed arachnoid granulations on both the lateral and medial sides of MC and posterior and anterior to the cave.…”

“…There are occasional ossifications or calcifications near MC and the porus trigeminus, such as ossifications of the posterior petroclinoid dural fold. Such ossifications can extend and involve a variable area of the petroclival dura [ 36 , 37 ]. Kimball et al [ 22 ] describe such ossifications as an anatomical variation causing the trigeminal nerve to traverse a bony foramen as it enters Meckel’s cave.…”