3D-Microarchitectural patterns of Hyperostosis frontalis interna: a micro-computed tomography study in aged women

Micro-computed Tomography Study of Frontal Bones in Males and Females with Hyperostosis Frontalis Interna

Hyperostosis frontalis interna (HFI) represents irregular thickening of the endocranial surface of the frontal bone, mostly seen in postmenopausal females. The microarchitecture of this condition is poorly studied. The aim of this cross-sectional autopsy study was to investigate and compare microarchitectural structure of the frontal bone affected with HFI in both sexes and to test whether HFI severity could be distinguished at the microarchitectural level. The sample was taken from human donor cadavers, 19 males (61 ± 15 years old) and 17 females (75 ± 15 years old). After classification of HFI severity (type A, B, C or D), samples of the frontal bone were taken and scanned using micro-computed tomography. Bone volume fraction was higher and total porosity lower only in the outer table of males with HFI, compared to females with HFI. Mean total sample thickness differed only between males with HFI type A and D. Bone microarchitecture between males and females with corresponding HFI types (e.g., male with type A versus female with type A) differed only in HFI type C regarding the fractal dimension of diploe. The degree of anisotropy differed between HFI subtypes in males, but the post hoc analysis revealed no significant differences between individual groups. Other microarchitectural parameters did not differ among males with different HFI subtypes, as well in females, in any part of the frontal bone. There is no difference in microarchitectural structure of the frontal bone between males and females with HFI, in general aspect and within corresponding HFI subtypes. HFI severity could not be distinguished at the microarchitectural level, neither in males nor in females.

A rare case of hyperostosis frontalis interna in an 86-year-old Japanese female cadaver

Hyperostosis frontalis interna (HFI) is a condition characterized by abnormal bone outgrowth on the inner surface of the frontal bone. Most HFI cases occur in post-menopausal elderly women. The pathology of HFI development is uncertain. The estimated incidence of HFI ranges from 5 to 12% in Western countries, but few cases have been reported in the Japanese population. Here, we report a case of HFI in an 86-year-old Japanese female cadaver. Macroscopically, the internal surface of the frontal bone exhibited bilateral nodular protrusion with sparing of the midline, while the external surface was normal. According to the morphological classification of HFI proposed by Hershkovitz et al. this case belongs to type D, the most severe type. Using computed tomography (CT), we defined five layers, designated as I-V from the inner to the outer layer, in the nodular region of HFI; however, the normal frontal bone is composed of three layers. Histological results demonstrated that layers I, III, and V consisted of the cortical bone, and layers II and IV consisted of the trabecular bone. We also observed increases in the numbers of lamellar bone and blood vessels on the dural side of layer I, indicating increased vascularization and active osteogenesis. These results indicate that layer II represents a new diploe within the inner table, which split into layers I and III, suggesting that diploization within the inner table by activated remodeling may be involved in the development of hyperostosis in this case.

Hyperostosis frontalis interna as an age-related phenomenon - Differences between males and females and possible use in identification

Hyperostosis frontalis interna (HFI) is a condition manifested by thickening of the inner surface of the frontal bone and it could be useful when dealing with the identification of human remains in various anthropological and forensic investigations. We compared the macroscopic appearance and morphologic (metric) features of the skulls in cases with and without HFI, in both sexes, and wanted to establish whether age determined occurrence of HFI. To achieve this aim, we performed prospective autopsy study, covering ten-year period (2007-2016). Study group consisted of southeast Europe Caucasian subjects, with determined age and sex. The severity of HFI was classified by two forensic pathologists independently, according to the four types (A-D) proposed by Hershkovitz et al. Thicknesses of the frontal and temporal bones, as well as the longitudinal and frontal diameters of the skulls were measured. The sample consisted of 35 males and 112 females with HFI, and 55 males and 202 females without HFI (404 individuals in total). Type B was the most common type of HFI among males (45%) and type C among females (41%). HFI type D was almost four times more common in females than in males (OR = 3.73). Frontal and temporal bones were thicker in all subjects who have HFI. Thickness of the skull was not age-dependent, in the entire sample, or in subjects with HFI, or in the control group (in all the cases Spearman's Rho was <0.3). Age seemed to be a predicting factor for HFI occurrence only in females. Females younger than 55 years have similar risk for HFI occurrence as males. An unidentified skull with the general markers of old age and severe form HFI is most probably from a female decedent.