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Concept: Foramen magnum

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BACKGROUND AND PURPOSE: The diagnosis of Chiari malformation type I (CMI) relies on MRI identification of a tonsillar descent (TD) through the foramen magnum, reflecting the overcrowding of an underdeveloped posterior cranial fossa (PCF). However, TD occurs in some patients with normal-sized PCF and, conversely, some patients with borderline or no TD have small PCF. We thus sought to identify a set of prototypic PCF measures for the diagnosis of CMI. METHODS: We performed nineteen measurements of the PCF on sagittal MRI of 100 cases with cerebellar TD ≥5 mm and 50 control individuals, compared the average values in both cohorts and used logistic regression to devise a probability model to predict CMI status. RESULTS: Significant decrements were detected for several PCF-related measures in the patients' cohort. We developed a probability model that combined seven of these parameters to predict diagnosis with 93% sensitivity and 92% specificity. CONCLUSIONS: The addition of simple morphometric measurements in the diagnostic work-up of patients with suspected CMI may facilitate radiological diagnosis. Moreover, identification of the subset of CMI that arise from basichondrocranium underdevelopment is important for both, selection of the most appropriate therapeutic approach as well as proper CMI categorization in research studies.

Concepts: Regression analysis, Positive predictive value, Type I and type II errors, Sensitivity and specificity, Foramen magnum, Arnold-Chiari malformation, Posterior cranial fossa

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Disruption or embryologic derailment of the normal bony architecture of the craniovertebral junction (CVJ) may result in symptoms. As studies of the embryology and pathology of hypoplasia of the occipital condyles and third occipital condyles are lacking in the literature, the present review was performed. Standard search engines were accessed and queried for publications regarding hypoplastic occipital condyles and third occipital condyles. The literature supports the notion that occipital condyle hypoplasia and a third occipital condyle are due to malformation or persistence of the proatlas, respectively. The Pax-1 gene is most likely involved in this process. Clinically, condylar hypoplasia may narrow the foramen magnum and lead to lateral medullary compression. Additionally, this maldevelopment can result in transient vertebral artery compression secondary to posterior subluxation of the occiput. Third occipital condyles have been associated with cervical canal stenosis, hypoplasia of the dens, transverse ligament laxity, and atlanto-axial instability causing acute and chronic spinal cord compression. Treatment goals are focused on craniovertebral stability. A better understanding of the embryology and pathology related to CVJ anomalies is useful to the clinician treating patients presenting with these entities. Clin. Anat., 2013. © 2013 Wiley Periodicals, Inc.

Concepts: Medical terms, Vertebral column, Skull, Normal distribution, Vertebral artery, Occipital bone, Medulla oblongata, Foramen magnum

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Sex estimation is a primary component of the identification of skeletonized individuals in forensic anthropology. The goal of this research was to develop a new method for estimating sex based on measurements of the endocranial cavity by means of volumetric 3D reconstruction of computed tomography (CT) without contrast. The sample consisted of 249 healthy individuals of both sexes whose tomographies were taken by the imaging unit at the San Vicente de Paul University Hospital in Medellin, Colombia. Sixteen measurements (twelve were designed for this study) of each individual’s endocranial base were taken and then used to create formulae via logistic regression, thereby yielding a 89.7% overall sex classification accuracy for the general equation. The measurements showing the greatest degree of sexual dimorphism were the maximum width of the basal occipital portion, the maximum width of the foramen magnum, and the maximum distance between foramina ovalia. This study represents the first physical anthropology study of this population.

Concepts: Volume, Medical imaging, Sexual dimorphism, Tomographic reconstruction, Sex, Units of measurement, Foramina of the skull, Foramen magnum

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Primary blast traumatic brain injury (bTBI) accounts for a significant proportion of wartime trauma. Previous studies have demonstrated direct brain injury by blast waves, but the effect of the location of the blast epicenter on the skull with regard to brain injury remains poorly characterized. In order to investigate the role of the blast epicenter location, we modified a previously established rodent model of cranium-only bTBI to evaluate two specific blast foci: a rostrally focused blast centered on the Bregma (B-bTBI), which excluded the foramen magnum region, and a caudally focused blast centered on the occipital crest, which included the Foramen Magnum region (FM-bTBI). At all blast overpressures studied (668-1880 kPa), rats subjected to FM-bTBI demonstrated strikingly higher mortality, increased durations of both apnea and hypoxia, and increased severity of convexity subdural hematomas, compared to rats subjected to B-bTBI. Together, these data suggest a unique role of the foramen magnum region in mortality and brain injury following blast exposure, and emphasize the importance of the choice of blast focus location in experimental models of bTBI.

Concepts: Traumatic brain injury, Skull, Rat, Subdural hematoma, Physical trauma, Occipital bone, Concussion, Foramen magnum

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To evaluate sexual-size dimorphism and attempt at categorization of inter-individual shapes of foramen magnum outlines using Fourier descriptors which allow for shape outline evaluations with a resultant specimen character definition.

Concepts: Similarity, Shape, Foramen magnum, Raccoon, Procyon, Supreme Headquarters Allied Powers Europe, Crab-eating Raccoon

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To compare whether there are any differences between the 3 methods used for measure area of foramen magnum (FM) in skulls.

Concepts: Comparison, Foramen magnum

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To retrospectively analyze the clinical data of 6 foramen magnum neurenteric cyst patients and summarizethe clinical characteristics and treatment experience for this rare disease in our single center.

Concepts: Epidemiology, Experience, Knowledge, Foramina of the skull, Foramen magnum

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Although the embryology of the posterior cranial fossa can have life altering effects on a patient, a comprehensive review on this topic is difficult to find in the peer-reviewed medical literature. Therefore, this review paper, using standard search engines, seemed timely. The embryology of the posterior cranial fossa is complex and relies on a unique timing of various neurovascular and bony elements. Derailment of these developmental processes can lead to a wide range of malformations such as the Chiari malformations. Therefore, a good working knowledge of this embryology as outlined in this review of its bony architecture is important for those treating patients with involvement of this region of the cranium. This article is protected by copyright. All rights reserved.

Concepts: Developmental biology, Skull, Peer review, Vertebra, All rights reserved, Copyright, Foramen magnum, Arnold-Chiari malformation

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We compared the cranial base of newborn Pax7-deficient and wildtype mice using a computational shape modeling technology called particle-based modeling (PBM). We found systematic differences in the morphology of the basiooccipital bone, including a broadening of the basioccipital bone and an antero-inferior inflection of its posterior edge in the Pax7-deficient mice. We show that the Pax7 cell lineage contributes to the basioccipital bone and that the location of the Pax7 lineage correlates with the morphology most effected by Pax7 deficiency. Our results suggest that the Pax7-deficient mouse may be a suitable model for investigating the genetic control of the location and orientation of the foramen magnum, and changes in the breadth of the basioccipital.

Concepts: Gene, Genetics, Geometry, Cranial nerves, Anatomy, Model, Mouse, Foramen magnum

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An upward displacement of the odontoid process into the foramen magnum was observed in the skeletal remains of a young male unearthed from a 14th-17th century cemetery in the north-eastern Italy. Examination of skull bone vestiges and CT-SCAN analysis of the axis exhibited a clear-cut contact zone between the odontoid process and the anterior border of the foramen magnum. In addition, the odontoid process appeared backward deviated. Findings suggest a possible diagnosis of basilar impression/invagination. This anomalous contact may cause compression of neural and vascular structures with a multifaceted series of clinical symptoms. We are unable to set our finding into a complete presumptive diagnostic outline because there is no chance to estimate either the magnitude of the whole CVJ defect but we believe that the present case contributes to the general knowledge of the craniovertebral region and to bone pathology in ancient times.

Concepts: Time, Scientific method, Bone, Skull, Philosophy of science, Foramen magnum, Ancient history, Axis powers