Is the Abducens Nerve Sometimes Duplicated at the Skull Base or Just Split? Anatomical and Histological Study with Applications to Skull Base Surgery

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. Conclusion: 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. Publication History Article published online: 27 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany