Background:The foramen magnum (FM) has garnered broad interest across the disciplines of anthropology, comparative anatomy, evolutionary biology, and clinical sciences. Most studies regarding the structure of the FM in humans have been intrapopulation morphometric studies rather than interpopulation morphologic studies. The few studies assessing the morphology of the foramen have utilized ambiguous and subjective descriptors to describe foraminal shape and are, consequently, difficult to reproduce. Therefore, detailed study of FM shape among craniofacially and geographically diverse populations through reproducible methods is warranted.Objectives:The aim of this study was to assess intersex and interpopulation differences in FM size and shape among diverse populations.Materials and Methods:The study analyzed 152 FMs of varied sex and race via traditional and geometric morphometric methods.Results and Conclusions:The study demonstrates that, within each distinct population, the size of the FM is significantly larger in males than in females; however, there are no significant differences in the shapes of the foramina between sexes. However, when comparing different populations to one another, there are significant differences with regard to both the size and shape of the FM. This study also presents a new model of FM ontogeny. Specifically, the growth occurring between the anterior and posterior foraminal boundaries before 5 years of age predicts the ultimate shape of the adult FM.

Metopism, the persistence of the metopic suture in adulthood, is a clinically significant radiographic finding. In addition to masquerading as a fracture of the frontal bone, a persistent metopic suture may be associated with other clinically significant anatomical variations including frontal sinus abnormalities. Several geographically and craniofacially distinct populations have yet to be assessed for the prevalence of metopism. This study aimed to determine the prevalence of metopic sutures in adult crania of diverse populations among which scant research exists. A total of 505 adult crania were examined for the presence of a metopic suture. A total of 13 (2.57%) demonstrated metopism. Among subpopulations, metopism was present in 8.06% (5:62) of European crania, 15.38% (2:13) of East Asian crania, 2.20% (2:91) of Egyptian crania, and 2.86% (1:35) of Bengali crania. Metopism was also found in 1 Chilean, Roman, and Tchuktchi cranium, respectively. Metopism was not seen in crania from individuals of African (non-Egyptian) descent (0:62), Peruvians (0:144), Malayans (0:23), or Mexicans (0:23). Among sexes, metopism was present in 3.77% (8:212) of females and 1.79% (5:279) of males. The prevalence of metopism differs between populations and sexes. The results of this study provide anthropological, developmental, and clinical insight with regard to metopism.

Identification of the infraorbital foramen is important in infraorbital nerve block and the prevention of iatrogenic injury of the infraorbital nerve in maxillofacial surgeries. This study assessed the location of 887 infraorbital foramina from 518 adult crania of varied sex and population. The study assessed the midpoint of a line segment spanning from nasospinale to jugale (NS-J) relative to the infraorbital foramen. The mean distance of the NS-J midpoint from the infraorbital foramen was 2.1 ± 1.9 mm (mean ± SD) with a mode of 0 mm (266:887; 30%). The NS-J midpoint was located in the same plane or inferior to the infraorbital foramen in 98.4% of sides (873:887). There were no significant differences between sexes, populations, or sides with regard to the NS-J midpoint to infraorbital foramen distance. The NS-J midpoint can be used to locate the infraorbital foramen in both females and males of varied populations regardless of craniofacial diversity. The results of this study will aid in infraorbital nerve block procedures and maxillofacial surgery.

The basioccipital bone is an essential developmental component to the occipital bone, occipital condyles, foramen magnum, clivus, and cranial base. The basioccipital bone joins each exoccipital bone with a basiexoccipital synchondrosis and the basisphenoid/sphenoid bone with a spheno‐occipital synchondrosis. The basioccipital is found intermediate to the petrous temporal bones and forms the bilateral petrooccipital/petroclival fissures otherwise known as the petrooccipital complex. Thus, the basioccipital bone is a central component to the developing cranial base. Despite the importance of basioccipital development in cranial ontogeny, there has been limited study of basioccipital ontogeny. This study assessed 98 disarticulated human basioccipital bones from a perinatal population ranging in age‐at‐death from 5‐months intrauterine to 5‐months post‐natal development. Size and shape of basioccipital bones were assessed with traditional and extended eigenshape geometric morphometric analysis. The results of this study demonstrate that the basioccipital bone grows in width at a faster rate than it grows in length. The maximum basioccipital width surpassed the midsagittal length at approximately 7‐months intrauterine development. Canonical variate analysis revealed statistically significant shape change occurring from a relatively narrow/elongate (anterior‐to‐posterior) basiocciput shape with mild concavity at the foramen magnum in the fifth and sixth intrauterine months to a relatively broad/stout basiocciput shape with more pronounced concavity in the postnatal months. Likewise, growth rate in total length was greater than midsagittal length, demonstrating enlargement of concavity in the anterior foramen magnum over time. This report provides insight into cranial development and aids in estimating age‐at‐death among fetuses and infants.

The infraorbital foramen was located within 2 mm, on average, from the nasospinale-to-jugale midpoint regardless of age group. Therefore, the nasospinale-to-jugale midpoint may serve as useful means of identifying the location of the infraorbital foramen in the pediatric population and aid in optimizing infraorbital nerve block procedures. The information in this report is valuable in general, but may be particularly useful in developing countries where there is a lack of ultrasound training and availability for health care providers; or places where infraorbital nerve block may be the sole anesthetic modality for cleft lip surgery, even among adolescent patients.

The basioccipital bone is particularly important with regard to the developing cranium. There is broad anatomical diversity in the anatomy of fetal and infantile basioccipitals. Specifically, some basioccipitals have transverse basilar clefts, clival foramina, and clival canals. Additionally, basioccipitals are diverse with regard to foveae and foveolae patterns. The size and shape of the basioccipital also changes throughout development. Canonical variate analysis revealed shape change from a relatively narrow/long with mild concavity at the foramen magnum in the 5th and 6th intrauterine months to relatively broad/short with more pronounced concavity in the 5th postnatal month. This report highlights the development of the basioccipital bone in addition to detailing the prevalence of the aforementioned anatomical features of the basioccipital and discusses the implications for anthropology, forensic osteology, as well as clinical implications of variant basioccipital anatomy.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Learning anatomical variations of the cranium poses unique difficulties particularly with regard to having physical access to crania with variations, adequate time to appreciate specimens, and an inherent lack of depth perception afforded from textbook images. This report documents the development of a repository of three‐dimensional (3D) scans of crania possessing both common and rare anatomical variations. Examples of such anatomical variations include metopism, plagiocephaly, elongate styloid processes, confluence of the foramen ovale and spinosum, elongate nasal bones, osteoma, clival foramina, mastoidal emissary foramina, and caroticoclinoid foramina. The utility of 3D scans overcomes many barriers to learning cranial variation. For example, by having a digitized model of a cranium, a student can interact with the model in three dimensions outside of a laboratory. It allows for time flexibility as well. Additionally, there are benefits beyond the primary goal of educating the student, which include eliminating concern for damage to crania from mishandling and concerns of theft.Support or Funding InformationWV Research Challenge Fund [HEPC.dsr.17.06] and [HEPC.dsr.14.13]This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The adult orbital rim is known to exhibit sexual dimorphism. However, the development of the orbital sexual dimorphism is poorly understood. Moreover, there has been little study of sexual dimorphism in the supraorbital rim in the early development of fontal bones. Therefore, this study assessed 188 supraorbital rims among black and white females and males of fetal, neonatal, and infantile age. The population consisted of 47 black female, 36 white female, 54 black male, and 51 white male supraorbital rims. Canonical variate analysis revealed statistically significant contour differences among all groups (p<0.0001). Further, all groups separated by Mahalanobis distances greater than 11 except for black females and white males (Mahalanobis distance = 6.84). The results of this study suggest that sexual dimorphism of the supraorbital rim exists within and between races, even among fetuses.Support or Funding InformationWV Research Challenge Fund [HEPC.dsr.17.06] and [HEPC.dsr.14.13]This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.