Neurocranial Length Research Articles

Breed-Specific Skull Morphology Reveals Insights into Canine Optic Chiasm Positioning and Orbital Structure through 3D CT Scan Analysis.

This study's CT scan-based morphometric analysis of 50 adult dogs explored the relationship between skull shape variations (determined by the skull index, SI), optic chiasm, optic canals, and orbital shape. Dogs were classified as brachycephalic (SI ≥ 59), mesocephalic (SI ≥ 51 but <59), and dolichocephalic (SI < 51). No significant age or weight differences were observed. Skull lengths (brachycephalic: 11.39 ± 1.76 cm, mesocephalic: 15.00 ± 2.96 cm, dolichocephalic: 17.96 ± 3.44 cm) and facial lengths (brachycephalic: 3.63 ± 1.00 cm, mesocephalic: 6.46 ± 1.55 cm, dolichocephalic: 8.23 ± 1.03 cm) varied significantly, with shorter orbital depths (brachycephalic: 2.58 ± 0.42 cm, mesocephalic: 3.19 ± 0.65 cm, dolichocephalic: 3.61 ± 0.77 cm) in brachycephalic dogs. The optic chiasm-to-inion horizontal length ratio to cranial horizontal length positively correlated with the SI (r = 0.883, p < 0.001), while the ratio to neurocranial length showed no SI correlation (range: 55.5-75.0). Brachycephalic breeds had a significantly wider optic canal angle (93.74 ± 16.00°), along with broader lacrimal-zygomatic and zygomatic frontal process angles. These findings highlight the zygomatic bone's role in influencing breed-specific orbital variations by connecting the face to the neurocranium, projecting the orbital rim outward and forward with facial shortening.

Comparison of a blind and an ultrasound-guided technique for Retrobulbar anesthesia in dogs undergoing unilateral subconjunctival enucleation.

This study compared the quality of retrobulbar anesthesia using a blind inferior-temporal palpebral approach (ITP) with an ultrasound-guided supratemporal (ST) technique in dogs undergoing unilateral enucleation. Twenty-one client-owned dogs were undergoing enucleation. Dogs were randomly assigned to receive ITP (n = 10) or ST (n = 11) with 0.5% ropivacaine at 0.1 mL/cm of neurocranial length. The anesthetist was blinded to the technique. Intraoperative data included cardiopulmonary variables, inhalant anesthetics requirement, and requirement for rescue analgesia (intravenous fentanyl 2.5 mcg/kg). Postoperative data included pain scores, sedation scores, and need for intravenous hydromorphone (0.05 mg/kg). Treatments were compared using Wilcoxon's rank sum test or Fisher's exact test as appropriate. Comparison of variables over time were tested using a mixed effect linear model on rank. Significance was set at p = 0.05. Intraoperative cardiopulmonary variables and inhalant requirements were not different between groups. Dogs receiving ITP required median (interquartile range, IQR) 1.25 (0, 2.5) mcg/kg intraoperative fentanyl while those receiving ST required none (p < 0.01). Intraoperative fentanyl was required in 5/10 and 0/11 of dogs in the ITP and ST groups, respectively (p = 0.01). Postoperative analgesia requirements were not significantly different between groups; 2/10 and 1/10 dogs in the ITP and ST groups, respectively. Sedation score negatively affected pain score (p < 0.01). The ultrasound-guided ST technique was more effective at decreasing intraoperative opioid requirements than the blind ITP approach in dogs undergoing unilateral enucleation.

Morphometric investigation of neurocranium in domestic cat (Felis catus)

This study was intended to investigate some aspects of the morphometric characteristics of the neurocranium in domestic cat (Felis catus) of Bangladesh. Twenty adult domestic cat including 10 males and 10 female were euthanized using diazepam (@ 20 mg/kg) and their skulls were macerated to give morphometric parameters. Student t-test with level of significance set at 5% (p &lt; 0.05) was used to analyze the obtained values. The mean (mean ± SE) neurocranial volume was 28 ± 0.97 ml, neurocranial length was 6.63 ± 0.77 cm, and the neurocranial height and index were 3.32 ± 0.38 cm and 49.83%, respectively. The mean height and width of the foramen magnum were 1.32 ± 0.09 cm and 1.35 ± 0.08 cm, respectively, while the foramen index was below 100 at 90.72 ± 4.93. Parameters for the foramen magnum index showed significant difference between both sexes at p &lt; 0.05. The foramen magnum showed shape variations and there were multiple hypoglossal foramina in over 80% of the cats. Foramen magnum index was positively correlated with neurocranial volume. The results were discussed in terms of the usage of morphologic and morphometric characteristics of cranium and skulls in several basic and clinical applications in cat such as estimation of the brain density and the use of the cat for cranial pressure experiments. DOI: http://dx.doi.org/10.3329/bjvm.v11i1.17302 Bangl. J. Vet. Med. (2013). 11 (1): 69-73

Demythologizing Arctodus simus, the ‘short-faced’ long-legged and predaceous bear that never was

ABSTRACT In this study, we review the previous evidence on the paleobiology of the giant, ‘short-faced’ bear Arctodus simus (Mammalia: Carnivora: Ursidae) and contribute new ecomorphological inferences on the paleobiology of this enigmatic species. Craniodental variables are used in a comparative morphometric study across the families Felidae, Hyaenidae, Canidae, and Ursidae. Principal components analyses (PCAs) do not show an ecomorphological adaptation towards bone-cracking or hypercarnivory in the ‘short-faced’ bear. In contrast, PCAs and discriminant analyses restricted to the craniodental data set of ursids suggest close morphological resemblance between A. simus and the extant omnivorous bears. In addition, the scaling of snout length on neurocranial length in bears indicates that the face of A. simus was not particularly short. Body mass estimates obtained from major limb bone measurements reveal that A. simus specimens of around 1000 kilograms were more common than previously suspected. Scaling relationships in extant bears of limb lengths on the least width of the femoral shaft (the variable best correlated with body mass) indicate that A. simus was not as relatively long-legged as previously thought. For these reasons, although the isotopic signature of A. simus has been interpreted as evidencing that it consumed large amounts of flesh relative to some contemporary populations of Ursus arctos, our results do not support the previous views of A. simus as a fast-running super-predator or as a specialized scavenger. In contrast, the picture that emerges from this study is one of a colossal omnivorous bear whose diet probably varied according to resource availability.

Description, new reconstruction, comparative anatomy, and classification of the Sterkfontein Stw 53 cranium, with discussions about the taxonomy of other southern African early Homo remains

Specimen Stw 53 was recovered in 1976 from Member 5 of the Sterkfontein Formation. Since its incomplete initial description and comparison, the partial cranium has figured prominently in discussions about the systematics of early Homo. Despite publication of a preliminary reconstruction in 1985, Stw 53 has yet to be compared comprehensively to other Plio-Pleistocene fossils or assessed systematically. In this paper, we report on a new reconstruction of this specimen and provide a detailed description and comparison of its morphology. Our reconstruction differs in important respects from the earlier one, especially in terms of neurocranial length, breadth, and height. However, given that Stw 53 exhibits extensive damage, these dimensions are most likely prone to much error in reconstruction. In areas of well-preserved bone, Stw 53 shares many cranial features with Homo habilis, and we propose retaining it within this species. We also consider the affinities of dental remains from Sterkfontein Member 5, along with those from Swartkrans and Drimolen previously assigned to Homo. We find evidence for sympatry of H. habilis and Australopithecus robustus and possibly Plio-Pleistocene Homo sapiens sensu lato in Sterkfontein Member 5. At Swartkrans and Drimolen, we find evidence of H. habilis. We also compare the morphologies of Stw 53 and SK 847 and find compelling evidence to assign the latter specimen to H. habilis, as has been proposed.

A new stethacanthid chondrichthyan from the lower Carboniferous of Bearsden, Scotland

ABSTRACT Exceptionally complete material of a new stethacanthid chondrichthyan, Akmonistion zangerli, gen. et sp. nov., formerly attributed to the ill-defined genera Cladodus and Stethacanthus, is described from the Manse Burn Formation (Serpukhovian, Lower Carboniferous) of Bearsden, Scotland. Distinctive features of A. zangerli include a neurocranium with broad supraorbital shelves; a short otico-occipital division with persistent fissure and Y-shaped basicranial canal; scalloped jaw margins for 6–7 tooth files along each ramus; a pectoral-level, osteodentinous dorsal spine with an outer layer of acellular bone extending onto a brush-complex of up to 160% of neurocranial length; a heterosquamous condition ranging from minute, button-shaped, flank scales to the extraordinarily long-crowned scales of the brush apex; and a sharply up-turned caudal axis associated with a broad hypochordal lobe. The functional implications of this anatomy are discussed briefly. The rudimentary mineralization of the axial skeleton and small size of the paired fins (relative to most neoselachian proportions) are contrasted with the massive, keel-like, spine and brush complex: Akmonistion zangerli was unsuited for sudden acceleration and sustained high-speed pursuit of prey. Cladistic analysis places Akmonistion and other stethacanthid genera in close relation to the symmoriids. These taxa are located within the basal radiation of the chondrichthyan crowngroup, but more detailed affinities are uncertain. They may represent a plesion series on the holocephalan stem lineage, or a discrete clade branching from the base of the elasmobranch lineage.

Growth changes in the craniofacial complex of the rat after prolonged papain administration

The purpose of the study was to evaluate by radiographic and biometric means the effects of prolonged papain administration on growth of the craniofacial complex, to gain further insight into the importance of cranial cartilage for skull enlargement during rapid skeletal growth (25 to 70 days of age). Fifty 21-day-old male Lewis strain rats were divided randomly into three groups. Group 1 ( n = 20) received 45 daily injections intraperitoneally of a 2% solution of crude papain in normal saline from 25 to 70 days of age. Group 2 ( n = 20) were given 30 daily injections at the same dose level from 40 to 70 days of age, and group 3 ( n = 10) served as untreated controls. Animals were weighed daily until 70 days of age and then every other day until killed at day 120. Submental-vertex and lateral skull radiographs were obtained at 25, 40, 53, 70, 90, and 120 days of age with standardized skull positioning and radiographic settings. Cephalometric measurements of 22 linear dimensions were made in each of 360 cephalograms, and the data analyzed statistically with Student's t test. Growth velocity curves were evaluated for evidence of catch-up growth. Body-weight gain by papain-treated groups was less than for controls (p < 0.001). Skull and nasal lengths, middle cranial base length, and sphenoidal length were significantly shorter (p < 0.001). Neurocranial length was also shortened, whereas neurocranial height and supraoccipital height increased. Reduction of skull dimensions was generally more pronounced in the earlier injected group. The effectiveness of catch-up growth was not constant and was more successful in the later injected group. Catch-up growth was effective for posterior nasal, neurocranial and supraoccipital heights, cranial width, and posterior cranial base length. The incomplete nature of catch-up growth may have been due to the particular timing and severity of the insult, the frequency of administration of the enzyme and the peak velocity of dimensional growth relative to the time of papain administration. (A M J O RTHOD D ENTOFAC O RTHOP 1994;105:270-8.)

Craniofacial abnormalities in mice with X‐Linked hypophosphatemic genes (Hyp or Gy)

X-Linked hypophosphatemia is the most common cause of metabolic rickets in humans and is characterized by a reduced renal TmP/GFR and hypophosphatemia. Clinically, these changes are associated with growth retardation including attenuated craniofacial growth, femoral and tibial bowing, and radiologic and histomorphometric evidence of rickets and osteomalacia. Similar mutations occur in mice at the Hyp and Gy gene loci. Direct craniometric measurements were made on mouse skulls to investigate the pattern of craniofacial growth differences in the Hyp/+, Hyp/Hyp and Gy/+ genotypes and to compare these to littermate normals in the C57BL/6J mouse strain. There was generalized attenuation in craniofacial growth in all mutants. The heterozygous Hyp and Gy mutants showed similar patterns of craniofacial growth with diminished neurocranial length, viscerocranial length, and mandibular height. The Gy/+ was significantly smaller than the Hyp/+ in neurocranial width. The homozygous Hyp mouse was not affected more severely than the heterozygous Hyp except in overall cranial length, nasal bone length, and mandibular length from mandibular foramen to third molar. In summary, the heterozygous Hyp and Gy mutant mice showed similar patterns of craniofacial growth. The homozygous Hyp mouse was not affected more severely than the heterozygous Hyp except in three of the 15 measured variables. Thus, these data demonstrate the almost complete dominance of the Hyp gene. In contrast, the Gy gene is incompletely dominant. The heterozygous Gy females survive, but the hemizygous Gy males do not, on a C57BL/6J background. This suggests that there is a family of closely linked genes on the X chromosome which, while similar in their effects on phosphate homeostasis, have differing mechanisms of action.

Dental and craniofacial development in the normal and growth-retarded human fetus.

Craniofacial and dental development were examined in 32 human fetuses, 22--42 weeks of gestational age, nine of which were classified as light-for-dates (LFD). Statistically significant differences were detected between the LFD and the normal group with respect to upper and lower jaw size and cranial base length but not in the case of neurocranial length, orbital height or deciduous molar crown size. The structures which are least affected by intrauterine growth retardation are those whose growth rate is normally either low throughout the second half of gestation or falls substantially during the 10 weeks prior to term.

The effect of extreme temperatures and starvation on the body proportions of the rat.

AbstractThe effects of extremely cold and hot environments on body proportions of rats were studied. These effects included changes in the length of the tail, trunk, extremities, cranio‐facial and nasal dimensions, in bone robusticity and bone shape, in the size of the ear and in some characteristics of the skin and hair. Since animals in both extreme temperatures fail to gain normal body weight, all changes were also studied in a group of starving rats. Because of the lower body weight and its concomitant reduction of body measurements, absolute values were avoided for analysis and all parameters were related to neurocranial length and trunk length. Such a triple experimental approach (response to cold, heat, and starvation) combined with a two‐fold frame of reference (neurocranial length and trunk length), as well as statistical corrections for body weight loss, made it possible to differentiate between nutrition‐specific and temperature‐specific responses under conditions of extreme temperature exposure. Moreover, some attention was given to endocrine pathways involved in some morphological changes. The methodological advantages of a multi‐experimental approach over a single‐experimental technique were demonstrated.

The role of basicranial synchondroses in flexure processes and ontogenetic development of the skull base.

AbstractThe contribution of the basicranial synchondroses in the growth of neurocranial length and ontogenetic development of the cranial base were investigated. The study concentrated on the midsphenoidal synchondrosis and its delayed fusion in nonhuman primates when compared to man, and on the spheno‐occipital synchondrosis. The mode and time of fusion of both growth centers were observed, and their role in the ontogenetic growth changes (flattening processes) of the cranial base were established. The chondrogenic ossification of midsphenoidal and spheno‐occipital synchondroses was studied on 20 skulls of Macaca mulatta females, ranging in age from newborn specimens to those 24 months old. The technique of in vivo tetracycline bone labeling was used for histologic evaluation of the material. Different chondrogenic growth patterns were observed in both synchondroses. The endochondral activity of the spheno‐occipital synchondrosis increased with age, from a nonactive narrow cartilaginous column in the neonatal specimen to a broad band with high chondrogenic ossification in the 24‐month‐old specimens. This growth center contributes to elongation of the posterior portion of the cranial base and is a secondary factor in its flexion.The midsphenoidal synchondrosis seems to be the primary factor in the mode of flexure of the cranial base in Macaques. This growth center is very active in the first ten months of life but later exhibits cessation of chondrogenic activity and long remains unfused. The first signs of fusion were observed as late as 72 months of age. At the same time, the continuous process of cranial base flattening showed the first signs of tapering off.