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.

The orbital phenomenon, cribra orbitalia, has long been a source of controversy, especially with regard to its nature, derivation, and relationship to anemia. Therefore, the external surfaces of orbital roofs were systematically examined microscopically in human skulls from historical collections. Superior orbital surfaces of 278 individual crania within the Hamann‐Todd collection were assessed at various magnifications using epi‐illumination microscopy to identify the presence of cribra orbitalia and characterize its nature. Also, 12 additional individuals with diagnosed anemia in the Hamann‐Todd collection were evaluated. Orbital roof alterations, present in one‐third of examined crania, had two discrete appearances: Vascular grooves (45%) and application of new bone in a vascular branching pattern on the orbit surface (55%). Porosity of the orbit was not observed. Evaluation of the orbits of 12 individuals with diagnosed anemia revealed one with a single deep defect, suggesting a space‐occupying phenomenon, but no evidence of bone accretion, vascular grooves, or porosity. Cribra orbitalia has often been lumped indiscriminately as an indicator of organismal stress, rather than identified as a indicating a specific etiology. Neither that perspective nor porosity are supported by high resolution examination of orbital roof changes. Recognition of the blood vessel imprint pattern falsifies previous speculations and provides a new paradigm. The actual character of cribra orbitalia is documented and new hypotheses generated. While population prevalence of cribra orbitalia seems excessive for explanation on the basis of these hypotheses, the imprints are clearly vascular in origin.

The structure of the foramen ovale of the sphenoid bone is clinically important, particularly with regard to surgical procedures that cannulate of the foramen such as percutaneous trigeminal rhizotomy for the treatment of trigeminal neuralgia, percutaneous biopsy of parasellar lesions, and electroencephalographic analysis of the temporal lobe among patients undergoing selective amygdalohippocampectomy. Differences in the morphology of the FO have been reported to contribute to difficulties in the cannulation of the FO. However, reports regarding the structure of the FO use subjective and ambiguous descriptions of morphology including “oval”, “truly oval”, “elongated oval”, “elongated”, “semicircular”, “almond”, “round”, “rounded”, “slit”, “irregular”, “D shape”, and “pear.” Therefore, it is necessary to describe the structure of the FO with reproducible objective morphometric data. This study analyzed 169 foramina to determine normative morphometric shape descriptions of the following: area, perimeter, circularity, solidity, axes of a best fit ellipse, aspect ratio, and roundness. The shape descriptors reported herein may aid in identification and description of structural variation in FO including bony projections encroaching upon the foramina and may improve surgical approaches to transovale cannulation.

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The debilitating pain of trigeminal neuralgia (TN) often necessitates neurosurgical intervention via percutaneous transovale cannulation. While most percutaneous treatments of TN are successful, severe adverse events resulting from failure to properly cannulate the foramen ovale (FO) have been reported. With regard to specific targeting of particular trigeminal divisions (i.e. V1, V2, V3, and combinations thereof), operative techniques have been described; however, these descriptions have not included specific angulation data. This anatomical study analyzed the angular relationship between the centroid and anteromedial- and posterolateral-most aspects of the FO and the boundaries of the trigeminal impression. The study is the first to detail the angular relationship between the FO boundaries and the boundaries of the trigeminal impression in dry human skulls relative to the coronal plane. The information may be used to prevent miscannulation and also target specific branches of the trigeminal nerve for optimal operative results.

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.

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Purpose-Submental anatomical variation is of clinical importance with regard to head and neck surgeries. One such anatomical variation is that of additional musculature joining the intermediate tendon of the digastric muscle to the midline of the mylohyoid musculature-a variation which this report refers to, accordingly, as an arrowhead variation. Though the arrowhead variation has been described in several case reports, it has not been subject to cross-sectional study. The purpose of this study is to determine the prevalence of the arrowhead variation. Methods-Prevalence of the arrowhead variation was assessed in 19 cadavers via gross dissection. Results-Two of the 19 cadavers (10.5%) were found to have arrowhead variations. The arrowhead variation was found in one male (1:11; 9.1%) and one female (1:8; 12.5%), respectively. Conclusions-This report demonstrates that the submental arrowhead variation of the anterior digastric and mylohyoid musculature has been reported in isolated case reports since the nineteenth century. This report is the first cross-sectional study of the arrowhead variant, identifying it in approximately one in ten individuals and in both sexes. Therefore, the presence of an arrowhead variation should be regularly considered with regard to diagnosis of submental masses. Likewise, the arrowhead variation should be considered in the preoperative planning of the myriad operations performed in the submental region.