Adult Apical Ligament of the Dens Lacks Notochordal Tissue: Application to Better Understanding the Origins of Skull Base Chordomas

Introduction The apical ligament has long been reported to contain notochord remnants and thus might serve as a site of origin of chordoma formation at the skull base. However, to our knowledge, the histologic study of the apical ligament using histologic staining specific for notochordal tissue has not been previously performed. Therefore the current study was undertaken. Methods Fifteen apical ligament samples underwent histologic examination with specific markers for notochordal differentiation. Results Across all samples, there was no indication of any notochordal remnants. Conclusions On the basis of our cadaveric study, the apical ligament does not contain notochord tissue and in adults should not be considered a remnant of this structure. Moreover, it is unlikely that the apical ligament gives rise to chordomas at the craniocervical junction under normal circumstances.