Prevalence and Morphometry of Occipital Foramen in Dry Skulls and its Clinical Implications.

The occipital emissary foramen (OEF) located on the occipital bone transmits the occipital emissary vein, which connects the occipital vein to the confluence of cranial venous sinuses. The OEF varies in incidence, number, size, and location. Knowledge of this foramen is essential for carrying out suboccipital and transcondylar surgeries without clinical implications. Hence, the study was planned. The aim of the present study is to elaborate on incidence, location, and morphometry consisting of the number and size of this foramen in light of clinical bearing in the context of the Indian population. The study was carried out in the Department of Anatomy using 80 skulls of unknown age and sex. The occipital bone of the skull was observed for the incidence, number, size, and location of the occipital emissary vein and associated clinical implications were elaborated. The incidence of occipital foramen was 36.25% and detected in 29 skulls. All these occipital foramina were patent. The mean diameter of this foramen was 0.6 mm. The most common location of these foramina was the left side of the foramen magnum, followed by the left side of the external occipital crest. The information about the incidence, number, size, and location of OEF is important to prevent catastrophic bleeding during surgery in the region of the occipital bone. The awareness of differential morphometry and morphology of occipital foramina is of great importance for neurosurgeons during suboccipital craniotomy and skull base surgeries, including far lateral and transcondylar approaches to access posterior cranial fossa for management of pathologies in the cranial cavity.

Preliminary study on cranial measurements and sexual dimorphism in skull bones of gaur (Bos gaurus gaurus, Smith 1827).

Cranial measurements have been widely used in various studies in wildlife sciences, ranging from understanding predator ecology to wildlife forensics. However, detailed description of morphometry and sexual dimorphism of the skull of gaur Bos gaurus gaurus is lacking. The present study was undertaken to determine the sexual dimorphism based on the cranial measurements of gaur. A total of 12 individual gaur skulls of male (n = 6) and female (n = 6) were studied in the field from the naturally deceased animals between January 2018 and December 2021 in different ranges of Bandhavgarh tiger reserve (BTR), Madhya Pradesh, India. The skull measurements were analysed using univariate and multivariate statistics to determine whether cranial dimensions could be used to differentiate male and female skulls reliably. A total of 43 morphometrical parameters grouped into nine indices were calculated. Select morphometrical parameters viz PL, GFL, AKI, LBB, LFB, GBEE, GBAN, BPOP and GTCH were significantly different (p < 0.05) between sexes, whereas GBAN were significantly higher in female skulls. The measurements demonstrated that the skull of the gaur was dolichocephalic as the profile length and the otion to otion breath in both male and female were <75% of the length. Overall, 28 linear measurements of both the sexes were statistically significant (p < 0.05; <0.01). The calculated indices revealed that the foramen magnum index in the female gaur were significantly higher. In calculated cranial indices the facial index (a) was higher in female and facial index (b) were higher in males. The two important parameters, facial breadth in facial index (a) and the greatest breadth in facial index (b) were positively correlated, though facial index (a) was statistically not significant between the sexes. The greater inner length of the foramen magnum in female skull resulted in foramen being oval whereas it was circular in males. These parameters were decisive for sexual dimorphism, skull comparison and craniological studies. This study ascertained that the frontal index and skull index had no significant influence and were not good indices for discriminating skulls between male and female. Based on the Principal Component Analysis, it was found that skull of male and female gaurs exhibits differences in cranial morphology viz. cranial profile length or total length (PL) and the least inner height of the temporal groove (LIHT). The findings of the present study provide baseline information on various craniometrical measurements of skull of gaur, indices and parameters for sex identification that can be effectively used in understanding sex biased predation ecology, provide base line information to describe variation across its geographic range, and in identifying skulls recovered in wildlife offence cases.

Topographic Anatomy and Pneumatization of the Posterior Clinoid Process in Chiari Type I Malformation.

OBJECTIVE: This study aimed to examine pneumatization and topographic location of the posterior clinoid process (PCP) in Chiari type I malformation (CIM) for skull base approaches. METHODS: Computed tomography images of 52 (23 males/29 females) CIM subjects aged 23.87 ± 16.09 years and 71 (26 males/45 females) healthy subjects aged 42.48 ± 21.48 years constituted the study universe. RESULTS: The distances of PCP to the foramen magnum (P = 0.037), superior orbital fissure (P < 0.001), foramen rotundum (P < 0.001), and foramen ovale (P < 0.001) were smaller, but the distance of PCP to the crista galli (P = 0.038) was greater in CIM patients, compared with normal subjects. In CIM, the fusion between PCP and the anterior clinoid process was observed in 9 sides (8.70%), while in controls it was observed in 12 sides (8.50%). PCP pneumatization was observed in 40 sides (38.50%) in CIM patients, while it was observed in 28 sides (19.70%) in normal subjects. These data displayed that PCP pneumatization was affected by CIM (P < 0.001). CONCLUSIONS: The distances of PCP to the crista galli and foramen magnum indicate the anterior fossa length and the posterior fossa depth, respectively; thus CIM patients have a longer anterior fossa and a shallow posterior fossa. In addition, the distances of PCP to the superior orbital fissure, foramen rotundum, and foramen ovale indicate the middle fossa width; hence CIM patients have less middle fossa width than normal individuals. CIM patients have an approximately 50% higher PCP pneumatization rate, and this may increase the risk of complications such as cerebrospinal fluid fistula during the application of posterior clinoidectomy.

Retrospective evaluation of the morpometric and morphological anatomy of the occipital condyle, hypoglossal canal and foramen magnum in Turkish populaton with CBCT.

PURPOSE: The aim of this study is to morphometrically and morphologically examine the occipital condyle, which is an important anatomical region in terms of surgery and forensic medicine, and its surrounding structures, to evaluate the change in mean values according to gender and age, and to evaluate the correlation of the measurements obtained. METHODS: 180 (90 men, 90 women) CBCT images selected from the archive of Ankara University Faculty of Dentistry. Occipital Condyle length and width, Hypoglossal Canal-Basion distance, Hypoglossal Canal-Opistion distance, Hypoglossal Canal-Occipital Condyle anterior and posterior border distance, Occipital Condyle thickness, Hypoglossal Canal length, the widest diameter of Hypoglossal Canal, the narrowest diameter of the Hypoglossal Canal, the length of the Jugular Tubercle, the width of the Jugular Tubercle, the anterior intercondylar distance, the posterior intercondylar distance, and the Foramen Magnum index were measured. At the same time, the presence of septum or spicule in the hypoglossal canal and protrusion of the occipital condyle were evaluated. The relationship of age, gender, anterior and posterior intercondylar distance, and foramen magnum index measurements with all measurements were examined. RESULTS: In our study, all measurements were repeated 1 month after the first measurements to evaluate the intra-observer agreement, and the agreement between the obtained measurements and the first measurements was evaluated by calculating the intraclass correlation coefficient and 95% confidence intervals. Men's measurements were found to be significantly higher than women's measurements. When the coefficients of concordance in all measurements were examined, it was observed that there was a perfect concordance. CONCLUSION: When the results of the study are evaluated, it is seen that the values ​​obtained are generally close to the studies related to CT. Considering this, an idea can be gained as to whether CBCT, which has a lower dose and less cost, can be used as an alternative to CT in studies to be conducted with more comprehensive and different methods in skull base surgical planning.

Sex estimation based on foramen magnum: a three-dimensional geometric morphometrics approach / Estimación del sexo basado en el foramen magno: un enfoque de morfometría geométrica tridimensional

SUMMARY: The foramen magnum is an important topographic opening which connects cranial cavity and spinal canal. The analysis of the bone material established that there are differences in the shape of the foramen magnum between individuals. The aim of this study was to determine sex based on shape and size of foramen magnum using geometric morphometrics method. A study was performed on three-dimensional models (3D models) of 214 human skulls of known sex and known age (141 male skulls and 73 female skulls). The skulls are located at the museum of Medical Faculty, University of Sarajevo. Skulls belong to Bosnian population from the mid-twentieth century. All examined skulls were scanned with a laser scanner to obtain their 3D models. On 3D models of the examined skulls, four landmarks were marked on foramen magnum. Analysis of sex determination was performed using the MorphoJ program. Results of this study showed that there are sex differences in the shape and size of the foramen magnum. Sex determination based on the shape and size of the foramen magnum was showed 65.25 % accuracy for male and 63.01 % accuracy for female using geometric morphometrics method. Examination of the effect of size of foramen magnum on sexual dimorphism of shape of foramen magnum showed a statistically significant effect. Sex determination based just on the shape of foramen magnum using geometric morphometrics method was possible with 62.41 % accuracy for male and 58.90 % accuracy for female on examined sample. Sex differences on shape and size of foramen magnum were found using geometric morphometrics method on three-dimensional models of the examined skulls. The percentage of accuracy was higher for male based on the shape and size of the foramen magnum than for female.

El foramen magno es una importante abertura topográfica que conecta la cavidad craneal y el canal espinal. El análisis del material óseo estableció que existen diferencias en la forma del foramen magno entre individuos. El objetivo de este estudio fue determinar el sexo en función de la forma y el tamaño del foramen magno utilizando morfometría geométrica. El estudio se realizó en modelos tridimensionales (modelos 3D) de 214 cráneos humanos de sexo y edad conocidos (141 cráneos masculinos y 73 cráneos femeninos). Los cráneos se encuentran en el museo de la Facultad de Medicina de la Universidad de Sarajevo. Los cráneos pertenecen a población bosnia de mediados del siglo XX. Todos los cráneos examinados fueron escaneados con un escáner láser para obtener sus modelos 3D. En los modelos 3D de los cráneos examinados, se marcaron cuatro puntos de referencia en el foramen magno. El análisis de determinación de sexo se realizó utilizando el programa MorphoJ. Los resultados de este estudio mostraron que existen diferencias de sexo en la forma y el tamaño del foramen magno. La determinación del sexo basada en la forma y el tamaño del foramen magno mostró una precisión del 65,25 % para los hombres y del 63,01 % para las mujeres utilizando morfometría geométrica. El examen del efecto del tamaño del foramen magno sobre el dimorfismo sexual de la forma del foramen magno mostró un efecto estadísticamente significativo. La determinación del sexo basada solo en la forma del foramen magno utilizando morfometría geométrica fue posible con una precisión del 62,41 % para los hombres y del 58,90 % para las mujeres en la muestra examinada. Se encontraron diferencias de sexo en la forma y el tamaño del foramen magno utilizando morfometría geométrica en modelos tridimensionales de los cráneos examinados. El porcentaje de precisión fue mayor para los hombres en función de la forma y el tamaño del foramen magno que para las mujeres.

Magnificent harmony in morphometric measurements of orbita and foramen magnum / Armonía magnífica en medidas morfométricas de órbita y foramen magno

SUMMARY: The foramen magnum (FM) is the key component of the craniovertebral junction, which connects the brain stem and medulla spinalis and is closely related to vital structures. FM dimensions are of great clinical importance. Considering the similarity in shape between FM and orbita, we thought that there might be a relationship between the lengths (sagittal diameter) and widths (transverse diameter) of these structures. Since it is not possible to reach FM directly, we set up our hypothesis as can we calculate the foramen magnum dimensions from orbital measurements before proceeding to costly tests. We also investigated this harmony in the skulls we used in the study. In the study, 21 dried skull bones from the Turkish population were used. FM and right Orbital length and width measurements were made. Precision digital caliper was used for measurements. Statistical validity and reliability analyzes were performed to prove the agreement between the measurements. We found that the length of the orbit and FM in the sagittal plane is close to each other, with 34.74±2.11 mm and 34.99±3.0 mm, and the width of the orbit in the coronal plane is approximately 1.40 times the width of the FM. We proved that the estimation of FM dimensions based on orbital measurements is also statistically valid and safe. Using orbital measurements, it is possible to estimate FM dimensions which are difficult to reach directly in living humans.

El foramen magno (FM) es el componente clave de la unión craneovertebral, que conecta el tronco encefálico y el bulbo raquídeo y está estrechamente relacionado con las estructuras vitales. Las dimensiones FM son de gran importancia clínica. Teniendo en cuenta la similitud de forma entre FM y órbitas, consideramos que podría haber una relación entre las longitudes (diámetro sagital) y las anchuras (diámetro transversal) de estas estructuras. Dado que no es posible llegar al FM directamente, establecimos nuestra hipótesis y calculamos las dimensiones del foramen magno a partir de mediciones orbitales antes de proceder a costosas pruebas. También investigamos esta armonía en los cráneos que usamos en el estudio. En el estudio, se utilizaron 21 huesos de cráneo secos de la población turca. Se realizaron mediciones FM y de longitud y anchura orbitales. Para las mediciones se utilizó un calibrador digital de precisión. Se realizaron análisis estadísticos de validez y confiabilidad para probar la concordancia entre las mediciones. Encontramos que la longitud de la órbita y FM en el plano sagital es cercana entre sí, con 34,74±2,11 mm y 34,99±3,0 mm, y el ancho de la órbita en el plano coronal es aproximadamente 1,40 veces el ancho de la FM. Demostramos que la estimación de las dimensiones FM basadas en mediciones orbitales también es estadísticamente válida y segura. Empleando mediciones orbitales, es posible estimar dimensiones FM que son difíciles de alcanzar directamente en humanos vivos.

Surgical anatomy of hypoglossal canal for various skull base surgeries.

PURPOSE: Anatomical knowledge of the hypoglossal canal is very important in relation to drilling of occipital condyle, jugular tubercle etc. So, this study was conducted to identify various morphometric and morphological features of the hypoglossal canal and its distance from adjacent structures relative to stable and reliable anatomic landmarks. METHODS: The study was performed on 142 hypoglossal canals of 71 adult human dry skulls. The parameters measured were the transverse, vertical diameter, depth of the hypoglossal canal. The distances from the hypoglossal canal to the foramen magnum, occipital condyle and jugular foramen were also noted. In addition, the different locations of the hypoglossal canal orifices in relation to the occipital condyle were assessed. The different shapes and types of the hypoglossal canal were also noted. RESULTS: There was significant difference (p < 0.05) in measurements taken on the right and left sides in males and females. The intracranial orifice of hypoglossal canal was present in middle 1/3rd in 100% of occipital condyle for both genders. The extracranial orifice of the hypoglossal canal was found to be in the anterior 1/3rd in 99% and 93.7% for male and female, respectively. Simple hypoglossal canal with no traces of partition was found to be more in males and females. The most common shape noted was oval both in males and females (71.8% and 68.7% respectively). CONCLUSION: The results of the dimensions of the hypoglossal canal and its distance from other bony landmarks will be helpful for neurosurgeons to plan which surgical approaches should be undertaken while doing various surgeries in posterior cranial fossa.

Radiologic Evaluation of the Fossa Navicularis on Dry Skull: A Comparative CBCT Study.

Fossa navicularis (FN) is defined as bony depression that is not always present and is located anterior to the foramen magnum and pharyngeal tubercle on the inferior aspect of the basilar part of the occipital bone. It has been reported that FN can create an infection spread path from the pharynx to the intracranial structures. Therefore, the diagnosis of this variation is important. Although cone beam computed tomography (CBCT) diagnostic accuracy has mostly been verified in detection and quantification particularly on human skulls, there is no study comparing morphometric measurements between direct measurement on the skull and CBCT measurement. The main object of this study is to evaluate the presence of FN on dry bones and CBCT images of the same dry skull and to examine the morphometric and morphological features of this formation. Thirty-two random craniums that were made available for this study that did not have any fractures or deformities of the cranial base were examined. The sagittal diameter, transverse diameter, and depth of the FN was measured both directly on dry skulls and radiologically on CBCT images of dry skull. In addition, the shape of FN (SFN) was determined. FN was detected in 10 (31.25%) of 32 craniums examined with both modalities. It was determined that sagittal diameter of the FN, transverse diameter of the FN, depth of the FN, and the shape of FN did not show a statistically significant difference between the 2 measurements. Unlike the literature, FN was investigated on dry bones both directly and in CBCT images in this study. In contrast to previously thought the FN may be smaller according to this findings, and this small variation can be detected with CBCT images. According to this findings, it can be said that morphometric evaluations on CBCT are accurate and reliable, and CBCT is a safe method for clinical diagnosis and treatment.

Sexual dimorphism and biomechanical loading in occipital bone morphological variation.

We explore the contribution of biological sex and biomechanical activity from subsistence to occipital bone variation. Previous studies have used occipital bone traits to determine biological sex and identify ancestry to differing degrees of success. Biomechanical stress from variation in subsistence and gender-based divisions of labor could perhaps explain some of the noise in the signal for these grouping variables. To explore this possibility, we used metric (foramen magnum length and breadth, external occipital protuberance depth, lambda-inion length, bicondylar breadth) and nonmetric traits (general occipital form, presence of a nuchal crest, and nuchal line count). We collected original data and mined published data for our analysis using skeletal collections of Native American hunter-gatherers and horticulturalists, a historic military site, and contemporary study collections. We find that the foramen magnum area exhibits sexual dimorphism and is not influenced by subsistence, but the accuracy of sex estimation is only 71%, suggesting the chance of being correct at slightly more than two-thirds. All traits exhibited sex-based variation but only bicondylar breadth and lambda-inion metrics exhibited subsistence-based variation. Given the limited amount of variance explained by either sex or sex and subsistence, biomechanics may still play a role but not from the influence of subsistence practices in these datasets. Additional data from a wider array of skeletal samples, perhaps with known occupation, is warranted if we are to understand how occipital variation is shaped.

Sex estimation using foramen magnum measurements, discriminant analyses and artificial neural networks on an eastern Turkish population sample.

BACKGROUND: Although many studies have been conducted using the foramen magnum for sex estimation, recent findings have indicated that the discriminant and regression models obtained from the foramen magnum may not be reliable. Artificial Neural Networks, was used as a classification technique in sex estimation studies on some other bones, did not used in sex estimation studies on the foramen magnum until now. The aim of this study was sex estimation on an Eastern Turkish population sample using foramen magnum measurements, discriminant analyses and Artificial Neural Networks. METHODOLOGY: The study was performed on the CT images of a total of 720 cases, comprising 360 males and 360 females. For sex estimation, discriminant analysis and Artificial Neural Networks were used. RESULTS: The accuracy rate was 86.7% with discriminant analysis and when sex estimation accuracy was determined according to cases with posterior probabilities above 95%, the accuracy ranged from 0% to 33.3%. With the use of the discriminant formulas of 2 other studies, obtained from different Turkish samples, sex could be determined at a rate of 84.6%. Some formulas were found to be unsuccessful in sex estimation. Sex estimation accuracy of 88.2% was achieved with Artificial Neural Networks. CONCLUSION: In this study, it was found that sex could be determined to some extent with discriminant formulas from other samples from the same population, although some formulas were unsuccessful. With the use of image processing techniques and machine learning algorithms, better results can be obtained in sex estimation.

Ossification of Pterygospinous and Pterygoalar Ligaments and Their Clinical Significance: An Anatomic Study.

ABSTRACT: Pterygospinous and pterygoalar ligaments, present in close proximity of foramen ovale at the base of skull, ossify creating pterygospinous and pterygoalar foramina, which causes problems in accessing retro and parapharyngeal spaces, trigeminal ganglion for treating trigeminal neuralgia by thermocoagulation and blocking it. Besides, these anatomical entities may compress nearby neurovascular structures causing discomfort to patients. Considering immense clinical significance associated with ossification of pterygospinous and pterygoalar ligaments, the study has been carried out. Aim of the study is to provide extended new classification related to pterygospinous and pterygoalar foramina and associated clinical significance. Seven hundred thirty skull bases were observed for variant ossification pterygospinous and pterygoalar ligaments and a new classification of occurrence of these anomalies has been proposed. Literature search revealed that incidence of formation of various forms of pterygospinous and pterygoalar foramina in world populations ranges between 1% and 31.2% and 1.3% and 62.4%, respectively. The highest incidence of complete pterygospinous foramen was observed in Brazilian population followed by Anatolian population and that of incomplete pterygospinous foramen also in Brazilian population. Various neurovascular structures are present in relation to pterygospinous and pterygoalar ligaments. Comprehension of foramina formed by ossification of these ligaments at the cranial base is imperative for proper planning and treating trigeminal neuralgia, clinical neuralgias involving oral and maxillofacial region and carrying out interventions like transfacial needle approaches to the foramen ovale and also for evaluating skull base radiographs. Therefore, thorough knowledge of these entities is of utmost use to anesthesiologists, dentists, and oral maxillofacial surgeons and neurosurgeons.

Golden ratio for the foramen magnum on CT images: a morphological and morphometrical study / Proporción áurea para el foramen magnum en imágenes de TC: un estudio morfológico y morfométrico

SUMMARY: The foramen magnum (FM) is a transition zone between the spine and skull. There is a study in the literature showing the golden ratio (4.62) and harmony between both FM and the anteroposterior and transverse diameters of the skull. The aim of this study is to examine the existence of this ratio on CT images and to investigate whether this ratio changes according to the FM shape types. In this study, 402 adult CT images belonging to the Turkish population were examined. Maximum cranial length (MCL), maximum cranial width (MCW) and the FM length (FML) and FM width (FMW) were measured. The different shapes of the FM were macroscopically classified. The number and incidence of each type in the studied skull was registered. In the 402 CT images used in the study, 12 FM shapes were detected. Three of the shape types observed in our study have not been reported in the literature until now, and were found in our study for the first time. In addition, our data supported that by using the ratio of 4.62, there was a great harmony between the skull and FM. The results obtained from the research show that there is a ratio of 4.62 between the basic cranial measurements and FM dimensions in all shapes except triangular shape. It is thought that repeating the calculated coefficients over more different FM shapes will contribute to the effectiveness of the proposed golden ratio.

RESUMEN: El foramen magno (FM) es una zona de transición entre la columna y el cráneo. Existe un estudio en la literatura que muestra la proporción áurea (4,62) y la armonía entre el FM y los diámetros anteroposterior y transversal del cráneo. El objetivo de este estudio fue examinar la existencia de esta relación en las imágenes de TC e investigar si esta relación cambia según los tipos de forma del FM. Se examinaron 402 imágenes de TC de adultos pertenecientes a la población turca. Se midieron la longitud craneal máxima, el ancho craneal máximo y la longitud del FM y la anchura del FM. Las diferentes formas del FM se clasificaron macroscópicamente. Se registró el número e incidencia de cada tipo en el cráneo estudiado. En las 402 imágenes de TC utilizadas en el estudio, se detectaron 12 formas de FM. Tres de los tipos de formas observados en nuestro estudio no se han reportado en la literatura consultada describiéndose por primera vez. Además, nuestros datos respaldaron que al usar la proporción de 4,62, había una armonía importante entre el cráneo y el FM. Los resultados obtenidos de la investigación muestran que existe una relación de 4,62 entre las medidas craneales básicas y las dimensiones de la FM en todas las formas excepto en la triangular. Se cree que la repetición de los coeficientes calculados en más formas de FM diferentes contribuirá a la eficacia de la proporción áurea propuesta.

Introducing the Posterior Condylar Emissary Vein as an Effective Surgical Landmark for Optimizing the Standard Retrosigmoid Approach: An Anatomo-Imaging Study.

OBJECTIVE: There is a lack of definite anatomical landmarks for the inferior extension of the standard retrosigmoid approach. In this study, we evaluated whether the posterior condylar emissary vein (PCEV) can be used as an intraoperative landmark for optimizing the surgical corridor. METHODS: We performed the standard retrosigmoid approach on 5 formalin-fixed and latex-injected cadaveric specimens and measured the distance between the PCEV near its bony canal and the vertebral artery (VA). In addition, vascular reconstructions of thin-sliced preoperative computed tomography (CT) scans were studied in 40 patients and the relationship between these 2 vessels was evaluated. An illustrative case is also included. RESULTS: The PCEV was consistently identified on both sides of cadaveric specimens and in 87.5% and 82.5% of the left and right sides of the included CT scans, respectively. The average distance between the part of the PCEV near its osseous canal and the VA was measured to be between 8.4 mm and 8.6 mm in the specimens and between 9.2 mm and 9.3 mm in the CT scans. This distance offers a safe and effective plane of dissection during the standard retrosigmoid approach and allows easy access to the foramen magnum. CONCLUSIONS: The PCEV near its bony canal proved to be an easy, straightforward, safe, and effective operative landmark with which the surgeon can extend the soft tissue dissection and bony exposure towards the foramen magnum. This maneuver provides ample access to the cisterna magna for cerebrospinal fluid drainage and increases visibility and surgical maneuverability to the entire cerebellopontine angle.

Morphometric Analysis of Posterior Fossa and Foramen Magnum among Pediatric Age Group 6 to 16 Years.

Background Configuration and size of the foramen magnum and posterior cranial fossa plays an important role in the pathophysiology of various disorders like Chiari malformations, basilar invagination etc. Thus, a fundamental knowledge of normal anatomy of this region is important to the clinician for diagnosis and treatment. However, we couldn't find any anatomical study related to the concerned topic among the pediatric population aged 6 to 16 years in Nepal to the best of our knowledge. Objective To attain the baseline results (volume of bony part of posterior cranial fossa and the surface area of foramen magnum) that will help in the better diagnosis, classification, and treatment of diseases related to posterior fossa and craniovertebral junction and serve as a future reference defining an anatomic range in our region. Method This is a retrospective prospective observational study conducted from 1st February 2021 to 31st January 2022 at Dhulikhel Hospital, Kathmandu University Hospital, Kavrepalanchowk, Nepal. We used convenient sampling technique to fulfil our sample size. We considered 68 patients, who got recruited either from our emergency and OPD departments and were fulfilling our criteria of inclusion. Upon the recruitment, 68 consecutive head CT scan of pediatric patients with normal reports (without any bony or soft-tissue abnormality) were studied. Volume of the posterior fossa was calculated with the help of inbuilt "advanced work station - 3D volume calculator" program in 128 slices - SOMATOM PERSPECTIVE CT Scanner from Siemens, Germany. The area of the foramen magnum was calculated using formula πr2 , where r is average radius calculated from obtained antero-posterior and transverse diameter. Result The age of the patients ranged between 6 and 16 years with the mean age of 10.56 ± 3.38 years with male to female distribution of 1: 1.125. The mean volume of the posterior fossa was 165.61 ± 8.52 mm3 . The mean AP diameter, transverse diameter, and the surface area of foramen magnum were 3.31 ± 0.12 mm, 2.72 ± 0.12 mm, and 28.60 ± 0.09 mm2 respectively. Conclusion Normal ranges of volume of posterior cranial fossa and various dimensions and surface area of foramen magnum of pediatric population were determined using CT scans, which could serve as future reference in Nepal.

Arterial Vascular Structures Running Through Retrotransverse Foramen and Retrotransverse Groove of the Atlas Vertebrae.

OBJECTIVE: Retrotransverse foramen (RTF) and retrotransverse groove (RTG) are anatomic variations of the atlas (C1) vertebrae. RTF contains an anastomotic vein connecting atlanto-occipital and atlanto-axodian venous sinuses. The purpose of this study was to analyze the arterial vascular structures running though the RTF and RTG. METHODS: Three-dimensional volume rendered computed tomography angiography (3D VR CTA) images of 427 patients (264 men, 163 women; age 17-87 years) were reviewed and evaluated using the RadiAnt DICOM Viewer (version 5.0.2; Medixant, Poznan, Poland). The incidence of RTF or RTG, the incidence of the V3 segment of vertebral artery variants, and the artery vascular structures inside the RTF and RTG anatomic variation of C1 were analyzed. RESULTS: Fifty (11.7%) atlases presented RTF anatomical variant; 113 (26.5%) atlases presented RTG anatomical variants. The incidence of the V3 segment of vertebral artery variants was 0.94% (4 of 427). Three (0.7%) were persistent first intersegmental artery and 1 (0.2%) was the fenestration of the vertebral artery on left side. In 4 cases of C1 vertebral artery V3 segmental variants, there were no RTF and RTG. No artery vascular structure was found in RTF or RTG. CONCLUSIONS: The RTF or RTG of C1 was a common anatomical variant. No arterial vascular structure runs though the RTF or RTG. The presence of C1 RTF and RTG variants had no effect on the V3 segmental course of the vertebral artery. Preoperative understanding of these variations using 3D CTA are helpful for the safe execution of the upper cervical posterior approach surgeries.

Sex estimation from foramen magnum parameters in adult Turkish population: A computed tomography study.

Identification of skeletal relics is crucial for medicolegal purposes. Sex estimation is one of the critical parts providing the identification of skeletal relics. In forensic practice, sex estimation requires multidisciplinary studies of such as forensic medicine, anatomy, dentistry and radiology. Recently, radiological studies on this subject have been increasing with the developing technology. The objective of this study is to examine the usage of radiological dimensions of foramen magnum for sex estimation in human skulls by developing discriminant functions in Turkish population. We analyzed 600 (300 males and 300 females) Computerized Tomography (CT) images of Turkish individuals aged between 21 and 50. Four measurements were obtained from CT images. All measurements in males were significantly greater than in females, and they provided the higher sex classification accuracy. The area of the foramen magnum calculated by Radinsky's formula was the best measurement for sex estimation with a 75% accuracy rate. In conclusion, the CT images of foramen magnum show sexual dimorphism in our population. To use population specific data would be the most appropriate approach for sex estimation.

Locomotion, posture, and the foramen magnum in primates: Reliability of indices and insights into hominin bipedalism.

The position (FMP) and orientation (FMO) of the foramen magnum have been used as proxies for locomotion and posture in extant and extinct primates. Several indices have been designed to quantify FMP and FMO but their application has led to conflicting results. Here, we test six widely used indices and two approaches (univariate and multivariate) for their capability to discriminate between postural and locomotor types in extant primates and fossil hominins. We then look at the locomotion of australopithecines and Homo on the base of these new findings. The following measurements are used: the opisthocranion-prosthion (OP-PR) and the opisthocranion-glabella (OP-GL) indices, the basion-biporion (BA-BP) and basion-bicarotid chords, the foramen magnum angle (FMA), and the basion-sphenoccipital ratio. After exploring the indices variability using principal component analysis, pairwise comparisons are performed to test for the association between each index and the locomotor and postural habits. Cranial size and phylogeny are taken into account. Our analysis indicates that none of the indices or approaches provides complete discrimination across locomotor and postural categories, although some differences are highlighted. FMA and BA-BP distinguish respectively obligate and facultative bipeds from all other groups. For what concerns posture, orthogrades and pronogrades differ with respects to OP-PR, OP-GL, and FMA. Although the multivariate approach seems to have some discrimination power, the results are most likely driven by facial and neurocranial variability embedded in some of the indices. These results demonstrate that indices relying on the anteroposterior positioning of the foramen may not be appropriate proxies for locomotion among primates. The assumptions about locomotor and postural habits in fossil hominins based on foramen magnum indices should be revised in light of these new findings.

A study on morphology and morphometric parameters on skull of the Bardhoka autochthonous sheep breed in Kosovo.

In this study, we aim to investigate the skull of Bardhoka sheep, which is the native breed of Kosovo by utilising normal morphometric methods. Differences between male and female were also statistically analysed. Further, the parameters that can be used in gender discrimination were also analysed. The statistical analysis was based on a sample of 24 adult skulls of Bardhoka breed with 12 female and 12 male skulls. Altogether, 31 different measurements were taken morphologically and 7 different indices were applied. Except for the measurement's values of the orbit, measurement's values of length of the cheek tooth row and the measurement's values of height of the foramen magnum, all the measured values of males were higher than females. Nasal index, cranium index and skull index values were statistically significant between both genders. It is envisaged that the findings of this study will motivate and assist other comparative studies with other autochthonous sheep and goat breeds found in the Dukagjini region or in clinical veterinary practice and even in zooarchaeology.

Vermian fossa or median occipital fossa revisited: Prevalence and clinical anatomy.

INTRODUCTION: The vermian fossa (VF1) is a small midline depression at the inferior end of the internal occipital crest (IOC2) near the foramen magnum. This study aims to accurately define the usual arrangement ("the norm") of the inferior end of the internal occipital crest, to determine the prevalence and dimensions of the VF in Central European population, and to state a possible correlation of the VF with anatomical variations and developmental abnormalities. MATERIALS AND METHODS: We analyzed the prevalence of the VF in 1042 dry skulls. The variable anatomy was classified into either the VF (four categories) or norm. Some rare variations of this region were also encountered. RESULTS: The norm was defined as a flat triangular prominence at the inferior end of the IOC, without any depression. As the most frequent arrangement, the norm appeared in 710 (68.14%) skulls. We observed the fossa in 309 (29.65%), type I in 264 (25.34%), type II in 45 (4.32%) and other rarer variations in 23 (2.21%), skulls, by our new classification system. CONCLUSION: Despite many different variations can be encountered in the posterior cranial fossa, the proper definition of the usual arrangement at the inferior end of the IOC is still missing. The knowledge of such anatomical variations is essential to decrease the risk of the hemorrhage from dural venous sinuses during surgical approach. Based on prevalence, the underdeveloped posterior cerebellomedullary cistern may occur along with the VF, and their common occurrence seems probable to have a relationship to Chiari malformation type I. As for the terminology, the term median occipital fossa seems to be more appropriate.

Estimation of height from the foramen magnum in the adult population - a preliminary study.

Stature estimation is an important early step during forensic analysis of human skeletal remnants. The aim of the present study was to obtain a linear regression formula for estimating stature from foramen magnum measurements of a central Indian population. The study includes 81 male and 55 female cadavers brought for medicolegal autopsies. The linear regression equations were derived from length (FML), breadth (FMB) and area (FMA) of foramen magnum. The regression model provided a 95% confidence interval of ± 11.1 cm, ± 10.4, and ± 10.5 cm and a correlation coefficient of 0.69, 0.75, and 0.74 for length, breadth, and area of male foramen magnum, respectively. Similarly, the regression model provided a 95% confidence interval of ± 13.4 cm, ± 11.4 cm, and ± 12.8 cm and a correlation coefficient of 0.45, 0.68, and 0.57 for length, breadth, and area of female foramen magnum. Compared to other studies, regression formulae based on the measurements of the foramen magnum provided slightly larger standard errors than that based on long bone lengths. The study indicates that foramen magnum measurements in relation with body stature show strong positive correlation, relatively moderate reliability in estimating stature, and some forensic value.