Newborn with isolated severe deficiency of cranial vault ossification: a case of cleidocranial dysplasia
Elena BorelliSalvatore AversaMario MottaElisa CavalleriClaudio CeredaLorenzo PinelliAlba PilottaFrancesco Maria Risso
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Cleidocranial Dysplasia
Cranial vault
In vertebrates, it has been argued that the development and evolution of an enlarged brain requires an increased basal metabolic rate or a compensatory reduction in the resources devoted to the formation of other metabolically costly tissues, leading to a reduction in the size of such organs. While the latter scenario is indirectly supported by comparative data, especially in primates, this inherently ontogenetic phenomenon has not been addressed in a mechanistic framework. Our experimental study investigates the relationship between brain growth and cranial development in ß-catenin transgenic mice with remarkably increased levels of prenatal neurogenesis. To evaluate associated changes in skull form and control for variation in maternal resources among mouse litters, we directly compare data from transgenic and wild-type littermates. Ossification patterns in the limbs and skull were also analyzed to control for within-subject variation in skeletal formation. Transgenic mice, with relatively larger brains, are characterized by a corresponding decrease in the degree of cranial ossification for a given age, in contrast to the presence of similar rates of postcranial ossification between transgenic and wild-type mice. This disparity is most pronounced in the neurocranial vault, which is supplied by a greater number of vessels in common with the brain than the facial skull. Mice with relatively larger brains had a decrease in cranial ossification. As modern humans are more encephalized than living apes and most extinct hominids, our findings provide unique insights into hominid evolution, particularly the “expensive tissue hypothesis” regarding energetic tradeoffs during neural and cranial development.
Cranial vault
Heterochrony
Postcrania
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Cleidocranial Dysplasia
Cranial vault
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During development, the embryonic cartilaginous skull in most vertebrates is partially replaced by bones with endochondral and perichondral ossifications. Muscle attachments are thought to influence the patterns of ossification and, hence, the differentiation of the skull. To investigate the association between muscle attachments and early ossifications of reptilian embryos, we conducted digital 3D reconstructions of the cranium, the head, and the neck musculature from a histological section series of a late term embryonic tuatara, Sphenodon punctatus, with a total body length of 52 mm. As the sole living rhynchocephalian species, it is an important outgroup in comparative studies of squamate evolution. We found that head and neck muscles are largely associated with early ossification of the basal plate and the palatoquadrate, and with three other ossifications in an older specimen with a total body length of 72 mm. These results suggest that tensile forces resulting from embryonic muscle contraction are largely, but not exclusively, correlated with the area of endochondral ossification in the chondrocranium and palatoquadrate in tuatara. Beyond little-known genetic factors, the complexity of chondrocranial architecture, the progress of its development, and the effect of multiple muscle transmitting forces in the chondrocranium must be considered to provide a more comprehensive discussion of the mechanical properties of the embryonic skull.
Endochondral ossification
Cranial vault
Neurocranium
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Abstract The osteocranium of a late embryo of the Egyptian snake, Psammophis sibilans (age, 58 days; total body length, 190 mm) has been described. Attention was given to the relation of the different bones to the adjacent cartilages of the chondrocranium as well as to the topographical relation of the bones to each other in the late embryonic state. Several adjacent bones have not yet come in contact with each other. The membrane‐bones make their appearance shortly before any sign of ossification in the cartilaginous cranium. The maxillary, palatine and pterygoid premordia have a slight earlier appearance than the other bony premordia. The lacrymal, postfrontal, squamosal, jugal, quadratojugal and epipterygoid bones are completely absent. The laterosphenoid bone is never performed in cartilage. The whole columella auris is ossified.
Columella
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The skeletogenesis and osteology of the syncranium of the redeye tetra Moenkhausia sanctaefilomenae is described. Skeletal development is rapid, with many elements of the chondrocranium and splanchnocranium well formed prior to the onset of ossification. The chondrocranium develops from an initial set of cartilaginous precursors, and continued elaboration proceeds from a series of processes which expand and converge to form the floor of the cranial vault, the otic capsule, the supraorbital bridge and the ethmoid region. Prodigious growth is observed for a number of splanchnocranial elements, including the Meckel's cartilage and the ceratohyal cartilage. Ossification occurs in overlapping phases with initial ossification of the jaws and neurocranial floor followed by the splanchnocranium, the supraorbital bridges and the ethmoid and cranial vault. Teeth are observed primarily on the premaxilla and dentary, while a single tooth is present on the maxilla. Particular cartilages, which had originally formed in the early larva, appear to degenerate and have no ossified representative in the adult syncranium. The cranial development for M. sanctaefilomenae is compared to those of other characiforms.
Cranial vault
Premaxilla
Osteology
Neurocranium
Intramembranous ossification
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Abstract The development of the skull of Dermophis mexicanus (Caeciliidae) is described and compared to that of other caecilians. The chondrocranium is well developed in embryos of 25 mm total length (TL); ossification begins in the quadrate and the articular element of the lower jaw at about 30 mm TL. The occipital arch then ossifies, followed by the dorsal and lateral dermal bones, then the ventral endochondral and dermal elements. The stapes ossifies at 55 mm TL. The amount of skull roofing increases during ontogeny, although the anterior rims of the nasal capsules, the anterior part of the mesethmoid, and the hyoid apparatus remain cartilaginous throughout life. Dermophis mexicanus lacks many primary embryonic ossification centers reported by Marcus et al. ('35) for Hypogeophis ; presence of these ossification centers has been presumed to be indicative of a primitive skull morphology derived with little modification from archaic amphibians (“stegocephalians”). The fetal skull is highly kinetic, and some kinesis is retained in adults. We suggest that fetal skull kinesis and early ossification of jaw suspension elements are functionally related to the intraoviducal feeding mode of this viviparous species. Based on this evidence, together with the observed ossification pattern and bone homologies, we conclude that stegokrotaphy (complete skull roofing) in caecilians is a derived condition, correlated with fossoriality, and does not indicate a direct relationship of caecilians to any known early amphibian taxon.
Neurocranium
Endochondral ossification
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Natrix
Cranial vault
Occipital bone
Colubridae
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The present paper considers the significance of a variety of cranial flexions in the process of orthocephalization of the rat skull between 14 and 60 days postnatally. The study is based on a sample of 27 male rats, who have been x-rayed at 14, 30 and 60 days with subsequent analyses of the photographs obtained. In this period the angle between the cranial base and the facial part of the skull becomes more obtuse, i.e. the skull becomes more orthocranial. The cranial base becomes at the same time more airobasal (lordotic). Angular changes between the individual bones in the cranial vault straightens the vault markedly. By this it becomes orthodorsal. As the angle between the basisphenoid and the parietal bones stays more or less constant between 14 and 60 days, the impression is created that both the anterior and posterior parts of the neural skull rotate upwards relative to this bone complex. Thus, orthocephalization in the period between 14 and 60 days both consists of flexions between the facial and neural parts of the skull (prebasal flexions), and may be more importantly of interosseous ventral and dorsal flexions.
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Parietal bone
Occipital bone
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Background The petroclival ligament (PL) forms the roof of Dorello's canal (DC). In humans, partial and complete ossification of this ligament have been reported. When completely ossified, DC is transformed into a bony foramen for the abducens nerve and accompanying vascular structures. As this osteological finding might have an impact on skull base surgery, this anatomical study was performed. Methodology Using 100 adult human skulls, the presence of an ossified PL was noted and classified. The diameter of the resultant bony foramen and laterality were documented. Additionally, PL was evaluated histologically in 10 heads. Results Overall, 8% of the sides were found to have partial or complete ossification of the PL. Partial ossification (type I) was noted on 3% of the sides. Completely ossified PL was identified on 5% of the sides. Some ossified ligaments (2.5%) were seen as an ossified bridge (type II), and others (2.5%) were converted into small foramina (type III). Three skulls (3%) were found to have a completely ossified ligament bilaterally. The mean diameter of the underlying DC was 0.8 mm. Partially ossified ligaments were statistically more likely to be on the right sides, and the diameter of the underlying DC was statistically smaller in type III. Histologically, the PL was found to have bone within it on three skull sides. Conclusions An ossified ligament can be found on imaging of the skull base. Moreover, during surgical approaches to the petroclival region and, specifically, DC, skull base surgeons should be cognizant of this anatomical variation.
Foramen
Osteology
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Abstract An appreciation of ontogenetic changes to the cranial base is important for understanding the evolution of modern human skull form. Using geometric morphometric techniques, this study explores midline shape variations of the basicranium and midface during human prenatal ontogeny. In particular, the analysis sets out to explore shape variations associated with endochondral ossification and to reassess shape variations previously observed on the basis of angular measures. Fifty‐four formalin‐preserved human fetuses were imaged using high‐resolution MRI. Coordinates for 10 landmarks defining the midline basicranium and midface were acquired and areas of ossification in the midline basioccipital, basisphenoid, and presphenoid cartilages were measured as percentages of overall cranial base area. The results show shape variations with increasing fetal size that are consistent with cranial base retroflexion, anterior facial projection and dorsal facial rotation. These growth variations are centered on the midsphenoid area and are associated with disproportionate variations of sphenoid height and length. Small but significant correlations were observed between ossification of the presphenoid cartilage and components of shape that described, among other variations, sphenoid shortening. While ossification cannot be directly linked with the shape variations observed, it seems likely that bone formation plays a role in modulating the influence of other factors on the fetal cranial base. Am J Phys Anthropol 2003. © 2003 Wiley‐Liss, Inc.
Endochondral ossification
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