2026 Poster Presentations
P071: IS THE ABDUCENS NERVE SOMETIMES DUPLICATED AT THE SKULL BASE OR JUST SPLIT? ANATOMICAL AND HISTOLOGICAL STUDY WITH APPLICATIONS TO SKULL BASE SURGERY
Brianna Hines1; Joseph Keen, MD2; Vernard Fennell, MD2; Joseph Lockwood, MD1; Noritaka Komune3; Carmine Donofrio4; Filippo Badaloni5; Antonio Fioravanti4; Aaron S Dumont1; Joe Iwanaga, DDS, PhD1,2,6; R. Shane Tubbs, PhD, MS, PAC1,2,6,7,8,9; 1Department of Neurosurgery, Tulane University School of Medicine, New Orleans, Louisiana, USA; 2Department of Neurosurgery and Ochsner Neuroscience Institute, Ochsner Health System, New Orleans, Louisiana, USA; 3Department of Otorhinolaryngology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; 4Department of Neurosurgery, ASST Cremona, Cremona, Italy; 5Department of Neurosurgery, IRCCS Istituto Delle Scienze Neurologiche di Bologna, Bologna, Italy; 6Department of Structural & Cellular Biology, Tulane University School of Medicine, New Orleans, Louisiana, USA; 7Department of Otolaryngology, Tulane University School of Medicine, New Orleans, Louisiana, USA; 8Department of Anatomical Sciences, St. George's University, St. George's, Grenada; 9University of Brisbane, Brisbane, Australia
Introduction: The abducens nerve is often encountered with approaches to the skull base. Some authors have reported that the nerve can be duplicated (supernumerary) at the skull base, where it pierces the dura mater overlying the clivus. The reported range for this is 6% to over 50%. We hypothesized that in such cases, there is not a frank duplication of the nerve but instead a splitting (bifurcating) of the nerve. This study was conducted to investigate the number of nerve fibers in normal and duplicated abducens nerves and to compare the results.
Methods: Ten duplicated abducens nerves at the entrance into the dura over the clivus and five normal abducens nerves were harvested in adult human cadavers. Both types of nerve were submitted for histological analysis, and nerve fiber counting was performed.
Results: Histologically, the total nerve fiber count in both duplicated and normal abducens nerves was approximately the same. Although the duplicated nerves were enveloped in their own connective tissue sheaths, the nerve fibers were more or less equivalent. No statistically significant differences were identified between the left and right sides or between male and female specimens.
Conclusions: Based on our cadaveric study, the term “duplication of the abducens nerve” should not be used. Both the split and normal abducens nerves carry approximately the same total number of nerve fibers. These findings will have application to skull base approaches near the abducens nerve.