Phenotypical variability of the skull base and its importance for neurosurgery

Maryna Al-Fauri

School of Health Sciences, Swinburne University of Technology

Objective: Although the phenotypical features of the calvaria of the skull are well described in the literature, the specifics of the morphology of the skull base structures related to the shape of the skull are not revealed yet. The goal of this study is to evaluate the influence of the shape of the skull on the morphology of the middle and posterior cranial fossae, the orientation of the pyramid of the temporal bone, and the localization of the sigmoid sinus.
Methods: The skull bases of 64 cadavers and 50 MR images of the head were digitized and studied with Photo Modeler and DICOM software. All specimens were subdivided into three study groups: dolichocephalic, mesocephalic, and brachycephalic.
Results: The inclination of the pyramid of the temporal bone forward was significant in the dolichocephalic group and approximated coronal plane in the brachycephalic group. Orientation of the pyramid influenced the positioning of the internal acoustic canal within the bone, which ran more forward and laterally in dolichocephalic ones. The sigmoid sinus was located lower and much closer to the external acoustic meatus in the brachycephalic group, but it ran much higher and further from the external acoustic meatus in the dolichocephalic specimens. These data are novel, and they show a clear pattern of distribution of the variables between the cranial phenotypes.
Conclusion: The cranial phenotype influences the orientation of the pyramid of temporal bone and internal acoustic canal, and the topography of the sigmoid sinus that should be considered by the related specialists.

Keywords: cranial phenotype; internal acoustic canal; sigmoid sinus; skull base; variability

Ethical statement: All body donors were legally competent and had a will in which they agreed to the use of their body for research, study, or teaching purposes; the patients who underwent radiologic examination have signed the written concern.

Funding statement: No funds were received.