Showing papers on "Skull published in 2001"

Paleohistopathology of bone: A new approach to the study of ancient diseases

Abstract: Light microscopy, particularly the use of polarized light, has such a high value for the differential diagnosis of dry bones that it can no longer be neglected. Alterations caused intra vitam by disease or other living conditions can clearly be differentiated by this technique from changes due to postmortem reactions (e.g., pseudopathology). As a reliable diagnosis is the basis not only of the study of case reports but also of the etiology and epidemiology of diseases in ancient populations, paleopathologists would be well-advised to employ histological analysis for their research, to avoid false diagnoses. The necessary basis for such research is the knowledge of the general histology, histogenesis, and growth as well as pathophysiology of bone. Some new techniques which facilitate the practical use of microscopic analysis, such as the preparation of thin-ground sections from undecalcified bone samples and nonrehydrated mummified soft tissues, are described. Selected examples of mechanisms of pathological bone changes, particularly the determination of vestiges of diseases in macerated bones by microscopy, are presented. Emphasis is placed on the differential diagnoses of proliferative reactions (e.g., periosteal processes of long bones and the skull). In this context, the importance of meningeal reactions on the endocranial lamina of the skull for morbidity and mortality in ancient populations is demonstrated. Furthermore, porotic hyperostosis of the skull vault and the orbital roof, i.e., the cribra cranii externa and cribra orbitalia, is discussed. Selected examples of the etiology and epidemiology of ancient diseases are presented (e.g., anemia, scurvy, rickets, and meningeal diseases), and ideas on living conditions and their implications for the origin and the spread of disease are given to establish a better understanding of deficiency and infectious diseases in the past.

Fibrous dysplasia involving the skull base and temporal bone

Abstract: Objective To gain a broader appreciation of the clinical presentation, operative treatment, and outcome of patients with fibrous dysplasia involving the skull base. Design Retrospective review of a clinical case series. Setting A single tertiary academic medical center. Patients Twenty-one patients with histopathologically confirmed fibrous dysplasia involving the skull base cared for over a 15-year-period (1983-1998). Main Outcome Measures Clinical and radiographic location of the fibrous dysplasia lesions within the skull base, clinical presentation, surgical intervention, and clinical outcome were tabulated for each patient. Results The ethmoids were most commonly involved (71%), followed by the sphenoid (43%), frontal (33%), maxilla (29%), temporal (24%), parietal (14%), and occipital (5%) bones. The most common presenting features included atypical facial pain and headache, complaints referable to the sinuses, proptosis and diplopia, hearing loss, and facial numbness. Surgical treatment, guided by clinical presentation, ranged from simple biopsy with conservative follow-up to craniofacial resection. Conclusions Fibrous dysplasia can present in myriad ways within the skull base. Modern imaging modalities and histopathologic analysis have made diagnosis relatively straightforward. Surgery, particularly in such a challenging region as the skull base, should be reserved for patients with functional impairment or a cosmetic deformity. Because of the benign nature of the condition, the surgery itself should be relatively conservative, with the primary goal being preservation of existing function.

Variations in size and in symmetry of foramina of the human skull.

Abstract: The goal of this report is to define an average size and size range for many of the skull's foramina and to determine in which paired foramina asymmetry is commonly found so that researchers and clinicians examining foramina may have an anatomical reference. The incidence of foraminal variations is also discussed. Information on skull foraminal size and symmetry is increasingly important because of the advancements in radiologic techniques such as magnetic resonance imaging (MRI) and computed tomography (CT). These methods are making difficult diagnoses of pathologic conditions of skull foramina possible. The foramina of 100 randomly selected dry skulls were measured and the symmetry of paired foramina was noted. The average, largest, and smallest sizes for 29 different foramina and the length of one canal are listed. Information regarding the symmetry of 27 paired foramina and the length symmetry of the infraorbital canal was also gathered. Specific data collected for paired foramina include the percent of skulls in which (1) neither foramen of the pair was present, (2) both foramina of a pair were present, (3) both foramina of the pair are present and were both the same size within 0.5 mm, and (4) both foramina of a pair are present but there was greater than 0.5 mm difference in size between them.

Simplification as a trend in synapsid cranial evolution.

Abstract: The prevalence and meaning of morphological trends in the fossil record have undergone renewed scrutiny in recent years. Studies have typically focused on trends in body size evolution, which have yielded conflicting results, and have only rarely addressed the question as to whether other morphological characteristics show persistent directionality over long time scales. I investigated reduction in number of skull and lower jaw bones (through loss or fusion) over approximately 150 million years of premammalian synapsid history. The results of a new skull simplification metric (SSM), which is defined as a function of the number of distinct elements, show that pronounced simplification is evident on both temporal (i.e., stratigraphic) and phylogenetic scales. Postcranial evolution exhibits a similar pattern. Skull size, in contrast, bears little relationship with the number of distinct skull bones present. Synapsid skulls carried close to their observed maximum number of elements for most of the La...

Derivation of the mammalian skull vault.

Abstract: This review describes the evolutionary history of the mammalian skull vault as a basis for understanding its complex structure. Current information on the developmental tissue origins of the skull vault bones (mesoderm and neural crest) is assessed for mammals and other tetrapods. This information is discussed in the context of evolutionary changes in the proportions of the skull vault bones at the sarcopterygian-tetrapod transition. The dual tissue origin of the skull vault is considered in relation to the molecular mechanisms underlying osteogenic cell proliferation and differentiation in the sutural growth centres and in the proportionate contributions of different sutures to skull growth.

Clinical Vascular Anatomy and Variations

Abstract: 1 General Introduction.- 2 Spinal and Spinal Cord Arteries and Veins.- 3 Craniocervical Junction.- 4 Skull Base and Maxillofacial Region.- 5 The Skull Base and Extradural Arteries.- 6 Intradural Arteries.- 7 Intracranial Venous System.- References.

Postweaning ontogeny of the skull of didelphis albiventris

Abstract: Postweaning development of the skull of Didelphis albiventris was studied in juveniles (3.5-8 months), subadults (7.5-9.5 months), and adults (>9.5 months). Analysis of allometry of 15 skull measurements was performed on a continuous growth series of 52-61 specimens to evaluate quantitative ontogenetic changes. Complex modifications occurred in cranial bones or regions such as the palate, processes for origin and attachment of jaw muscles, mandibular joint, frontal region, braincase, occipital bones, and petrosal. All measurements except zygomatic breadth were either positively or negatively allometric. Neurocranial components grew with strongly negative (<1) coefficients of allometry. Adult proportions of the masticatory apparatus arose from the counteraction of developmental trends; for example, the space for large temporal muscles was provided by isometric growth of the zygomatic breadth versus slower growth of the braincase. We interpret most of the postweaning developments as a function of the shift from milk suckling to active mastication.

An Embryonic Oviraptorid (Dinosauria: Theropoda) from the Upper Cretaceous of Mongolia

Abstract: An embryonic oviraptorid skeleton is described within an egg from the Late Cretaceous Djadokha Formation of Ukhaa Tolgod, Mongolia. The specimen comprises the ventral part of the skull and most of the mandible, a poorly preserved axial skeleton missing most of the tail, and portions of the forelimbs, shoulder girdles, pelvis, and hindlimbs. The skull is readily referable to the theropod dinosaur clade Oviraptoridae on the basis of several skull specializations (edentulous, vertically oriented premaxilla, a sinusoidally shaped lower jaw, and an unusual articulation of the vomer and premaxilla), and the postcranial skeleton is consistent with this identification. The egg is equivalent in overall shape and microstructure to those found beneath several oviraptorid skeletons recovered from the same formation. The skeleton is well ossified and, in comparison with ossification patterns in living Aves, the evidence suggests that this species was closer to the precocial end of the precocial-altricial spec...

The effects of skull thickness variations on human head dynamic impact responses

Abstract: Variations in human skull thickness affecting human head dynamic impact responses were studied by finite element modeling techniques, experimental measurements, and histology examinations. The aims of the study were to better understand the influences of skull thickness variations on human head dynamic impact responses and the injury mechanisms of human head during direct impact. The thicknesses of the frontal bone of seven human cadaver skulls were measured using ultrasonic technology. These measurements were compared with previous experimental data. Histology of the skull was recorded and examined. The measured data were analyzed and then served as a reference to vary the skull thickness of a previously published three-dimensional finite element human head model to create four models with different skull thickness. The skull thicknesses modeled are 4.6 mm, 5.98 mm, 7.68 mm, and 9.61 mm. These models were impacted by a cylinder with a mass of 5.23 kg and an initial velocity of 6.33 m/s. Model responses were compared between models in terms of intracranial pressures, head impact accelerations, brain shear stresses, and skull von Mises stresses. It has been shown that the thickness of the skull influenced the dynamic responses of the head during direct impact. As skull thickness increased, skull deformation decreased as the skull absorbed less impact energy. However, this relationship cannot be linearly interpolated to the other parameters such as head acceleration and intracranial pressure responses. Based on model responses to half-sine wave pulses, skull and brain iso-stress curves were constructed for the thicker and thinner skulls. Thresholds for skull fracture and reversible concussion were established for the population represented by these skulls.

New genus of dorudontine archaeocete (cetacea) from the middle‐to‐late eocene of south carolina

Abstract: A new archaeocete whale from the late middle or early late Eocene of South Carolina, Chrysocetus healyorum gen. et sp. nov., is described on the basis of a single subadult specimen. This individual includes: a partial skull; hyoid apparatus; lower jaws; teeth; all cervical, some thoracic and some lumbar vertebrae; ribs and sternum; left forelimb elements; and pelves. The specimen includes portions of much of the body, but while some of the bones are fairly complete, others are damaged, particularly the skull. The pelves resemble those of Basilosaurus, documenting a similar stage of hind limb reduction in dorudontines and suggesting that Chrysocetus was not able to support its body on land. The acetabulum for articulation of the femur is well formed and indicates that the hip joint was functional. Chrysocetus is distinguishable from other described dorudontines based on body size, characteristics of the teeth, and forelimb elements. Absence of deciduous teeth in a subadult individual of Chrysocetus may be indicative of an early stage of the evolution of monophyodonty.

In vivo surface strain and stereology of the frontal and maxillary bones of sheep: implications for the structural design of the mammalian skull.

Abstract: Does the skull of the sheep behave as a tube or as a complex of independent bones linked by sutures? Is the architecture within cranial bones optimized to local strain alignment? We attempted to answer these questions for the sheep by recording from rosette strain gauges on each frontal and maxillary bone and from single-axis gauges on each dentary of five sheep while they fed on hay. Bone structure was assessed at each rosette gauge site by stereological analysis of high-resolution radiographs. Structural and strain orientations were tested for statistical agreement. Ranges of strain magnitudes were +/-1200 mu epsilon on the mandible, +/-650 mu epsilon on the frontals, and +/-400 mu epsilon on the maxillae. Each gauge site experienced one strain signal when on the working (chewing) side and a different one when on the balancing (nonchewing) side. The two signals differed in mode, magnitude, and orientation. For example, on the working side, maxillary gauges were under mean compressive strains of -132 mu epsilon (S.D., 73.3 mu epsilon), oriented rostroventrally at 25 degrees -70 degrees to the long axis of the skull. On the balancing side, the same gauges were under mean tensile strains of +319 mu epsilon (S.D., 193.9 mu epsilon), at greater than 65 degrees to the cranial axis. Strain patterns on the frontals are consistent with torsion and bending of the whole skull, indicating some degree of tube-like mechanical behavior. Frontal and maxillary strains also showed a degree of individual loading, resulting from modulation of strains across sutures and local effects of muscle activity. The sheep skull seems to behave as a tube made of a complex of independent bones. Structural orientation was in statistically significant agreement with the orientation of working-side compressive principal strain epsilon 2, even though principal tensile strains may be as large or larger. Cranial bone architecture in sheep is not optimized to both strain signals it experiences.

The development of the skull in Acrochordus granulatus (Schneider) (Reptilia: Serpentes), with special consideration of the otico-occipital complex.

Abstract: The skull of Acrochordus has been characterized by the absence of a crista circumfenestralis (a synapomorphy shared by all snakes), and by the absence of a recessus scalae tympani that in other squamates forms by subdivision of the embryonic metotic fissure. These traits have variably been identified as either plesiomorphic or paedomorphic. The study of the development of the osteocranium in a series of cleared and stained embryos of Acrochordus shows a close correspondence to the development of the skull in other snakes. The exception is the formation of the postorbital from two ossification centers. The significance of this observation, which might suggest the embryonic fusion of a postfrontal with a postorbital, remains enigmatic, as it is based on one side only of the skull of a single specimen. By contrast, a rudimentary and modified crista circumfenestralis can be identified in the skull of Acrochordus. Furthermore, absence of a recessus scalae tympani is not due to an undivided fissura metotica, but results from the obliteration of the anterior part of the metotic fissure instead. With respect to this character, Acrochordus is neither plesiomorphic, nor paedomorphic, but autapomorphic. This interpretation of the skull of Acrochordus is compatible with the sister-group relationships this genus shares with colubroid snakes. J. Morphol. 249:252–266, 2001. © 2001 Wiley-Liss, Inc.

Development of the bony skull in common sole: brief survey of morpho‐functional aspects of ossification sequence

Abstract: The postembryonic development of the bony cephalic skeleton in the common sole Solea solea, observed from hatching to the juvenile stage or postmetamorphic larva, appears to follow a similar chronological order to that observed in other Pleuronectiformes and Perciformes and the sequence in bone formation is a response to functional demands. At hatching, S. solea has no bony structure. On day 4, only the outlines of maxillaries and opercular bones are visible. On day 6, a thin parasphenoid appears between the orbits and isolates the braincase from the buccal cavity making food ingestion possible without any impact on the brain. On day 8, the dentaries form and two small preopercular bones appear on each side of the head. On day 9, at weaning from the yolk sac, branchial arches support the gill filaments (used for respiration and trapping phytoplankton which pass through the open mouth). On day 10, the premaxillaries develop in front of the maxillaries, The superimposing of the maxillaries and the premaxillaries is a typical feature of species possessing an acanthopterygian protractile mouth at the adult stage. On day 12, the frontals develop above the orbits and the set of opercular bones is complete. On day 18, the migration of the left eye begins. On day 20, the left eye has moved to the median crest of the head. On day 23, both eyes are located on the same side. On day 26, the braincase is formed by a basioccipital, exoccipitals, pterotics, sphenotics and a supraoccipital. On day 50, new structures have appeared, others have developed and have undergone an extensive remodeling due to metamorphosis.

Postnatal Msx1 expression pattern in craniofacial, axial, and appendicular skeleton of transgenic mice from the first week until the second year.

Abstract: Phenotypes associated with Msx1 mutations have established the prominent role of this divergent homeogene in skeletal patterning. Previous studies have been achieved during antenatal development in relation with the early death of null mutant mice. Therefore, the present study is devoted to Msx1 homeogene in the postnatal craniofacial, axial, and appendicular skeleton. A knock-in transgenic mouse line was studied from the first postnatal week until 15 months. Whole-mount β-galactosidase enzymology identified Msx1 protein expression pattern. Maintained expression of Msx1 was observed in growing and adult mice, specifically in the sites where Msx1 plays an early morphogenetic role during initial skeletal patterning. These included the craniofacial sutures, autopodium, mandible, and alveolar bone. Furthermore, active membranous and endochondral bone formation involved Msx1 in the entire skeleton. Histologic sections showed that progenitor as well as differentiating and differentiated cells of all the bone cell lineages could express the Msx1 protein (chondrocytes, osteoblasts, tartrate-resistant acid phosphatase positive osteoclasts and chondroclasts). Recent developments in the genetic and developmental biology of skeletal morphogenesis demonstrate that genes critical for development are jointly expressed in discrete embryonic signalling and growth centers, the enamel knot in teeth, the cranial suture in skull morphogenesis, and the progress zone in the limb buds. The present study suggests that these signalling pathways are jointly important throughout the entire lifetime with an exquisite site-specificity spatially related to early patterning. © 2001 Wiley-Liss, Inc.

The cranium of Parapithecus grangeri, an Egyptian Oligocene anthropoidean primate

Abstract: A nearly complete skull of Parapithecus grangeri from the early Oligocene of Egypt is described. The specimen is relatively undistorted and is undoubtedly the most complete higher primate skull yet found in the African Oligocene, which also makes it the most complete Oligocene primate cranium worldwide. Belonging in superfamily Parapithecoidea, a group regarded by some as the sister group to all other Anthropoidea, this skull reveals important information about the radiation of stem anthropoideans. This cranium is about 15% larger than size estimates based on a fragmentary cranium of its contemporary and close relative Apidium phiomense. It is about the same size as that of the gray gentle lemur, Hapalemur griseus, or of platyrrhines such as the owl monkey, Aotus trivirgatus, or the titi monkey, Callicebus torquatus. Comparatively small orbits and size differences in jaws and teeth show it was both diurnal and dimorphic. This is the only specimen of the species that shows (from sockets) that there were four small upper incisors. Several mandibular specimens of the species establish that there were no permanent lower incisors and that the symphysis was fused. Like other early anthropoideans this species possessed a lower encephalization quotient and less-developed orbital frontality than later anthropoideans. There is full postorbital closure and fusion of the metopic suture, and the ectotympanic forms a rim to the auditory aperture. A probable frontal/alisphenoid contact is a potentially derived resemblance to Catarrhini. A proposed separate genus for the species P. grangeri is not sustained.

Cranial morphology of the anguilliform clariid Channallabes apus (Günther, 1873) (Teleostei: Siluriformes): are adaptations related to powerful biting?

Abstract: Within the clariids (air-breathing catfish), a complete range of fusiform to anguilliform species can be observed. This study deals with the cranial morphology of Channallabes apus, an extreme anguilliform (eel-like) species, compared to the anguilliform Gymnallabes typus and the more fusiform Clarias gariepinus. The overall morphology of the head of Channallabes apus shows a hypertrophied adductor mandibulae complex, with the corresponding substantial narrowing of the neurocranium, seen in the frontals, the sphenotics, the pterotics and the posttemporo-supracleithra, as well as the reduction and displacement of the eyes and some canal bones, such as the infraorbitals and the suprapreopercles. The presence of a hypertrophied muscle complex possibly indicates that a more powerful bite may occur. This implies that adaptations can be expected in several parts of the skull. On the lower jaw of C. apus a higher coronoid process is found, and on the suspensorium, two sets of three processes are present on the hyomandibular bone, indicating a stronger connection to the neurocranium. Several of the observed features, such as the elongation of the body, the reduction of the eyes, the increase in vertebrae number, limblessness and the increasing rigidity of the skull, may also be related to a process of miniaturization.

A case of body stalk anomaly at 10 weeks of gestation

Abstract: We describe a case of body stalk anomaly which was diagnosed at 10 weeks of gestation on a dating scan. The fetus was visualized within the exocelomic cavity outside an apparently intact amniotic membrane. The fetus displayed multiple anomalies characteristic of body stalk syndrome including a skull and brain defect, abdominal wall defect, kyphoscoliosis and gross deformities of the lower limbs. These findings do not support early amniotic membrane rupture as the primary event in the pathogenesis of body stalk anomaly and indicate that the exocelomic location of the fetus may actually be one of the features of this complex developmental anomaly.

Surgical correction of scaphocephaly: experiences with a new procedure and follow-up investigations.

Abstract: Introduction: Simple resection of the sagittal suture and the use of alloplastic material or extensive skull resections have long been proven to be unsatisfactory in the treatment of sagittal synostosis. In contrast to these experiences, the immediate correction of skull shape seems to yield the best results without significant morbidity. Patients: Thirty-six scaphocephalic infants with an average age of 6.5 (3.5-14) months underwent operation by our craniofacial team since 1994. Methods: Wide resection of the sagittal suture was used in combination with a bone-strip resection along the coronal and lambdoid sutures. Occasionally partial resection and reshaping of the frontal or occipital bone was necessary to correct an extremely bulging skull. The cranial growth and shape was monitored by anthropometric skull measurements in the last 20 patients. Results: Except in two cases, in which the dura mater was minimally injured intraoperatively, no complications occurred in any patient. Craniofacial oedema always occurred but disappeared after 72 h. The immediate correction of the skull shape was successful in all cases and was completed within 6 months postoperatively. There was no iatrogenic bone defect one year after surgery. Postoperative skull shape and growth was normal. Conclusion: These procedures seem to be effective in the treatment of scaphocephalus. Further normalization of skull shape is achieved by unrestricted postoperative brain growth. Copyright 2001 European Association for Cranio-Maxillofacial Surgery.

The development of the tooth pattern and dentigerous bones in Polypterus senegalus (Cladistia, Actinopterygii).

Abstract: Summary The formation sequence of the tooth-bearing bones and the tooth pattern in early ontogeny of Polypterus senegalus is investigated using transparent preparation, histological sections, and SEM. During the attachment step of the yolk-sac larva the first dermal bones and teeth are formed. Teeth appear simultaneously in the areas of the maxillary, dentary, dermopalatine, prearticular, and coronoid 1 along with the first separate anlagen of these bones. A monostichous arrangement of primary teeth is established on the maxillary, dentary, and dermopalatine. Polystichous tooth arrangements do not occur before the early pterolarval phase, and then only in connection with bones of the palate and inner dental arcades. Especially pronounced is the influence of tooth formation on the structure of the parasphenoid that becomes much thickened by accretion of denticulate platelets, but we found neither evidence for a distinct vomeral contribution to the parasphenoid, nor a composite origin of the ectopterygoid in ontogeny. First replacement teeth are found in association with the maxillary and dentary as early as the late apterolarval phase. Primary teeth are of a single general type, whereas from the pterolarval phase onward three tooth types can be distinguished that are restricted to certain tooth bearing bones. Relatively late in ontogeny, dermo-metapterygoid and entopterygoid become formed and colonised by teeth, whereas first branchial teeth and tooth plates appear earlier during the first phase of extrinsic larval feeding. Characteristics of development of the dentition are discussed in comparison with character states of other better known fossil and recent taxa among Actinopterygii and Sarcopterygii. Compared to the assumed basic pattern of actinopterygian fishes, Polypteriformes show a derived condition with respect to structure, arrangement, replacement, and differentiation of teeth, which arises in sequence during larval development. This also corresponds to observed changes of feeding behaviour and functional demands during larval life.