Methodological aspects of differentiation of hyperostosis frontalis interna based on computed tomography of the skulls

Hyperostosis frontalis interna (HFI) is a pathological condition characterized by bilateral thickening of the inner surface of the frontal bone. HFI is often an incidental finding during routine clinical examinations of patients by computed tomography. The etiology of the condition is currently unknown, but HFI commonly appears with a number of metabolic disorders and hormonal dysfunctions. According to studies, hyperostosis frontalis interna is more common in women than in men. Frequency of HFI is increasing in the modern population. In this study, 195 CT scans of mature individuals of various sex and ages were analyzed using the Amira 2020.1 software: 145 CT scans of skulls from from the collections of the Anuchin Research Institute and Museum of Anthropology, Moscow State University and 50 CT scans of Israeli Bedouins from the Institute's exchange collection (with the University of Tel-Aviv, Israel). Nine cases of hyperostosis frontalis interna (5 in males and 4 in females) were found among the analyzed scans. A three-step algorithm for identifying HFI was generated, as well as criteria for distinguishing hyperostosis frontalis interna from other endocranial bony overgrowths. The integrity of the skull, the condition of the frontal bone and other skull bones should be evaluated to exclude diffuse pathological changes which are morphologically close to HFI. Also a researcher should pay attention to the localization of the growths, their boundaries and prevalence. The condition of the diploe and endocranial plate of the frontal bone should be evaluated and compared it with other layers in other bones of the skull on 2D slices. Evaluation of the relief of the internal surface of the frontal bone should be performed on 2D slices in different sections. The pathology should be distinguished using data of localization, prevalence, involvement of other bone structures of the skull, as well as the condition of the diploe and inner surface of the frontal bone. The method can be useful for a comparative study using morphological and radiological criteria, which will help to exclude doubtful cases during analyzing pathology on paleoanthropological material.