2025 Poster Presentations
P073: GRUBER'S LIGAMENT IS SIMPLY DURA MATER
Joe Iwanaga1; Rarinthor Samrid1; Joseph R Keen2; Blair M Barton2; Vernard S Fennell2; Noritaka Komune3; Aaron S Dumont1; R. Shane Tubbs1; 1Tulane University School of Medicine; 2Ochsner Health System; 3Kyushu University
Introduction: Gruber’s ligament, also known as the petroclinoid ligament or petrosphenoidal ligament, is a fibrous structure in the clival region of the skull base. Located within the inferomedial paraclival triangle, it forms the roof of Dorello’s canal, through which the abducens nerve, dorsal meningeal artery, and inferior petrosal sinus travel. Our previous study revealed that the anterior attachment of Gruber’s ligament was onto the lateral clivus instead of the posterior clinoid process and suggested that “petroclival ligament” is the appropriate term for this structure. Gruber’s ligament is an important surgical landmark for localizing the abducens nerve during the transclival/petrosal approach to skull base surgeries. Occasionally, it is ossified or even absent. However, current understanding cannot explain the reasons for its absence and variations. Also, its morphology is still controversial, potentially affecting the concept of Dorello’s canal. Therefore, this study aimed to evaluate the gross anatomy and histology of Gruber’s ligament to elucidate its morphology and comprehensively assess its clinical relevance.
Methods: Ten formalin-fixed cadaveric heads were used. First, paracoronal sections of Dorello’s canal were observed microscopically using Masson’s Trichrome staining. Secondly, the structure was subjected to gross anatomical dissection under the surgical microscope; the posterior clinoid fold and trigeminal root/ganglion were removed. Two different approaches were applied, i.e., superior (conventional) and inferior. In the conventional approach, the incision was made on the dura deep to the trigeminal root/ganglion, and the superficial part of the dura was removed from superior to inferior until the abducens nerve was exposed. In the inferior approach, the incision was made on the clival dura inferior/medial to the entrance of Dorello’s canal until the scalpel touched the bony clivus, and the dura/periosteum was elevated from inferior/medial to superior/lateral until it passed over the petrous apex to reach the middle cranial fossa.
Results: Histological observation identified no separate/independent or distinct ligamentous structure as superior to the abducens nerve except dura. Gross anatomical dissection with the conventional approach identified fibrous connective tissue as a roof of the abducens nerve running between the clivus and petrous apex of the temporal bone. Using the inferior approach, the removed tissue was dissected from the deep surface. There was only dura superficial (superior) to the abducens nerve with no separate ligamentous structure. No distinct ligamentous tissue was observed.
Conclusions: This study has demonstrated that Gruber’s ligament is an artifact of the dura resulting from dissection. This finding will clarify the anatomy of Dorello’s canal so the transclival/petrosal approaches can be performed more accurately.