Stem cells of the suture mesenchyme in craniofacial bone development, repair and regeneration.

Development of the skeleton is mediated through two distinct ossification mechanisms. Craniofacial bones are formed mainly through intramembranous ossification, a mechanism different from endochondral ossification required for development of the body skeleton. The skeletal structures are quite distinct between the two, thus they are likely to have their unique stem cell populations. The sutures serve as the growth center critical for healthy development of the craniofacial skeleton. Defects in suture morphogenesis cause its premature closure, resulting in development of craniosynostosis, a devastating disease affecting 1 in ~2,500 individuals. The suture mesenchyme has been postulated to act as the niche of skeletal stem cells essential for calvarial morphogenesis. However, very limited knowledge is available for suture biology and suture stem cells (SuSCs) have yet to be isolated. Here we report the first evidence for identification and isolation of a stem cell population residing in the suture midline. Genetic labeling of SuSCs shows their ability to self-renew and continually give rise to mature cell types over a 1-year monitoring period. They maintain their localization in the niches constantly produce skeletogenic descendants during calvarial development and homeostastic maintenance. Upon injury, SuSCs expand drastically surrounding the skeletogenic mesenchyme, migrate to the damaged site and contribute directly to skeletal repair in a cell autonomous fashion. The regeneration, pluripotency and frequency of SuSCs are also determined using limiting dilution transplantation. In vivo clonal expansion analysis demonstrates a single SuSC capable of generating bones. Furthermore, SuSC transplantation into injured calvaria facilitates the healing processes through direct engraftments. Our findings demonstrate SuSCs are bona fide skeletal stem cells ideally suited for cell-based craniofacial bone therapy as they possess abilities to engraft, differentiate.(Presented at the 1980th Meeting, April 16, 2019).

Internal and external sagittal craniovertebral alignment: A comparison between radiological and photogrammetric approaches in asymptomatic participants.

BACKGROUND: Photogrammetric measures are a commonly applied, highly reliable tool for appraising craniovertebral postures during clinical assessments, rehabilitation, and research interventions. OBJECTIVE: This study aimed to compare and contrast three external measures of postural alignment (EMPA) using photogrammetric and radiological approaches, and to discuss whether the craniovertebral angle (CVA) reflects the shape of the underlying cervical spine. DESIGN: Cross Sectional Correlation Study. METHOD: Young adults attended three assessment sessions (S1, S2 and S3). S1 involved a standardised photogrammetric protocol. S2 involved radiographic image acquisition. S3 followed the same protocol in S1 but excluded the self-balancing procedure. Each session's EMPA were compared through either paired or independent samples t-tests. The different radiographic cervical subtypes and their corresponding CVAs were assessed. RESULTS: There were no significant differences in any EMPA between the two photogrammetric sessions. The CVA was the only EMPA to show a significant difference between photogrammetric (S3) and radiographic approaches. Cervical subtype variability is present throughout the full CVA range. CONCLUSIONS: Despite the statistically significant difference in the CVA between approaches, the mean difference was small and unlikely to be clinically meaningful. Accordingly, the quantification of EMPA can be undertaken with high levels of precision and reliability using standardised photogrammetric procedures. The CVA, however, does not provide an indication of the shape of the underlying cervical spine. The distinct radiological differences in the inter-segmental orientation of each vertebral motion segment in conjunction with the differences in the overall global cervical alignment, both within and between participants, negate this possibility.

Evaluation of strain values of critical anatomic regions for two different pterygomaxillary approaches in Le Fort I osteotomy: An experimental study.

BACKGROUND: The purpose of this experimental study was to measure stresses both on the pterygoid plates and the skull base following two different pterygomaxillary approaches in Le Fort I osteotomy. MATERIAL AND METHODS: The prepared skull models were randomly divided into 2 groups of 7. In the first group (A), the pterygomaxillary area was left intact. In the second group (B), pterygomaxillary separation was performed with a fine bur. The stresses were measured by using strain gauges. These strain gauges were attached to 6 different anatomical sites. The skull models were mounted on a servo-hydraulic testing unit. Each model was then subjected to a continuous linear tension until a plastic deformation was seen. RESULTS: The statistical analyses showed that there were no significant differences (p>.05) between the 2 groups regarding the strain values. Moreover, no statistical differences (p>.05) were found between the two groups in terms of maximum applied forces. CONCLUSIONS: Considering the clinical conditions, the present study shows that when Le Fort I osteotomy performed without pterygomaxillary separation, there is no significant stress on the skull base during the downfracture. Moreover, it is considered that there is no need for an excessive force applied to perform downfracture in Le Fort osteotomies without pterygomaxillary separation.

Failure pressures after repairs of 2-cm × 2.5-cm rhinologic dural defects in a porcine ex vivo model.

BACKGROUND: The objective of this study was to determine failure pressures of 6 rhinologic repair techniques of large skull base/dural defects in a controlled, ex vivo model. METHODS: Failure pressures of 6 dural repairs in a porcine model were studied using a closed testing apparatus; 24-mm × 19-mm dural defects were created; 40-mm × 34-mm grafts composed of porcine Duragen (Integra), fascia lata, and Biodesign (Cook) were used either with or without Tisseel (Baxter International Inc.) to create 6 repairs: Duragen/no glue (D/NG), Duragen/Tisseel (D/T), fascia lata/no glue (FL/NG), fascia lata/Tisseel (FL/T), Biodesign/no glue (B/NG), and Biodesign/Tisseel (B/T). Saline was infused at 30 mL/hour, applying even force to the underside of the graft until repair failure. Five trials were performed per repair type for a total of 30 repairs. RESULTS: Mean failure pressures were as follows: D/NG 1.361 ± 0.169 cmH2 O; D/T 9.127 ± 1.805 cmH2 O; FL/NG 0.200 ± 0.109 cmH2 O; FL/T 7.833 ± 2.657 cmH2 O; B/NG 0.299 ± 0.109 cmH2 O; and B/T 2.67 ± 0.619 cmH2 O. There were statistically significant differences between glued (Tisseel) and non-glued repairs for each repair category (p < 0.05). CONCLUSION: All glued repairs performed better than non-glued repairs. Both D/T and FL/T repairs performed better than B/T repairs. No repair tolerated pressures throughout the full range of adult supine intracranial pressure.

Fetal Tendinous Connection Between the Tensor Tympani and Tensor Veli Palatini Muscles: A Single Digastric Muscle Acting for Morphogenesis of the Cranial Base.

Some researchers contend that in adults the tensor tympani muscle (TT) connects with the tensor veli palatini muscle (TVP) by an intermediate tendon, in disagreement with the other researchers. To resolve this controversy, we examined serial sections of 50 human embryos and fetuses at 6-17 weeks of development. At 6 weeks, in the first pharyngeal arch, a mesenchymal connection was found first to divide a single anlage into the TT and TVP. At and after 7 weeks, the TT was connected continuously with the TVP by a definite tendinous tissue mediolaterally crossing the pharyngotympanic tube. At 11 weeks another fascia was visible covering the cranial and lateral sides of the tube. This "gonial fascia" had two thickened borders: the superior one corresponded to a part of the connecting tendon between the TT and TVP; the inferior one was a fibrous band ending at the os goniale near the lateral end of the TVP. In association with the gonial fascia, the fetal TT and TVP seemed to provide a functional complex. The TT-TVP complex might first help elevate the palatal shelves in association with the developing tongue. Next, the tubal passage, maintained by contraction of the muscle complex, seems to facilitate the removal of loose mesenchymal tissues from the tympanic cavity. Third, the muscle complex most likely determined the final morphology of the pterygoid process. Consequently, despite the controversial morphologies in adults, the TT and TVP seemed to make a single digastric muscle acting for the morphogenesis of the cranial base.

Morphology of the human cervical vagus nerve: implications for vagus nerve stimulation treatment.

OBJECTIVES: The vagus nerve has gained a role in the treatment of certain diseases by the use of vagus nerve stimulation (VNS). This study provides detailed morphological information regarding the human cervical vagus nerve at the level of electrode implant. RESULTS: Eleven pairs of cervical vagus nerves and four pairs of intracranial vagus nerves were analysed by the use of computer software. It was found that the right cervical vagus nerve has an 1.5 times larger effective surface area on average than the left nerve [1,089,492 ± 98,337 vs 753,915 ± 102,490 µm(2), respectively, (P < 0.05)] and that there is broad spreading within the individual nerves. At the right side, the mean effective surface area at the cervical level (1,089,492 ± 98,337 µm(2)) is larger than at the level inside the skull base (630,921 ± 105,422) (P < 0.05). This could imply that the vagus nerve receives anastomosing and 'hitchhiking' branches from areas other than the brainstem. Furthermore, abundant tyrosine hydroxylase (TH)- and dopamine ß-hydroxylase (DBH)-positive staining nerve fibres could be identified, indicating catecholaminergic neurotransmission. In two of the 22 cervical nerves, ganglion cells were found that also stained positive for TH and DBH. Stimulating the vagus nerve may therefore induce the release of dopamine and noradrenaline. A sympathetic activation could therefore be part of mechanism of action of VNS. Furthermore, it was shown that the right cervical vagus nerve contains on average two times more TH-positive nerve fibres than the left nerve (P < 0.05), a fact that could be of interest upon choosing stimulation side. We also suggest that the amount of epineurial tissue could be an important variable for determining individual effectiveness of VNS, because the absolute amount of epineurial tissue is widely spread between the individual nerves (ranging from 2,090,000 to 11,683,000 µm(2)). CONCLUSIONS: We conclude by stating that one has to look at the vagus nerve as a morphological entity of the peripheral autonomic nervous system, a composite of different fibres and (anastomosing and hitchhiking) branches of different origin with different neurotransmitters, which can act both parasympathetic and sympathetic. Electrically stimulating the vagus nerve therefore is not the same as elevating the 'physiological parasympathetic tone', but may also implement catecholaminergic (sympathetic) effects.

Three-dimensional geometric morphometric analysis of the nasopharyngeal boundaries and its functional integration with the face and external basicranium among extant hominoids.

The nasopharynx is a centrally located but understudied upper respiratory tract component. This study tested hypotheses related to the functional integration of the nasopharyngeal boundaries with the facial skeleton and external basicranium over the course of development in humans and nonhuman hominoids. It was hypothesized that facial morphology (width, length, and kyphosis) is related to nasopharyngeal width and choanal morphology, whereas relative external basicranial proportions are related to nasopharyngeal depth. Human infants were used as models of extreme orthognathy and external basicranial retroflexion, whereas nonhuman hominoids were used to model greater relative prognathism and external basicranial retroflexion. Both of these groups were contrasted against adult humans, who exhibit both extreme orthognathy and external basicranial flexion. Three-dimensional landmark coordinate data were collected from age-graded series of Homo, Pan, Gorilla, Pongo, and Hylobates. Generalized Procrustes Analysis was performed, and multivariate shape differences were evaluated via principal components analysis. Additionally, linear measures were extracted from the Procrustes-corrected sets of landmark data. Results indicate that human adults are indeed distinct from all groups in possessing a relatively shallow nasopharyngeal roof and shorter, more flexed external basicranial axis. Human adults and infants both exhibit greater relative choanal and nasopharyngeal width. Nonhuman hominoid faces tended to become airorhynch into adulthood, whereas humans exhibited the opposite trend. When pooling all the hominoids, facial width and palate length were strongly correlated with choanal and nasopharyngeal width, whereas facial kyphosis was strongly correlated with choanal orientation. The hypotheses were supported as the results indicated a morphologic relationship among nasopharyngeal boundaries, the facial skeleton, and the external basicranium.

Biomechanical evaluation of the craniovertebral junction after inferior-third clivectomy and intradural exposure of the foramen magnum: implications for endoscopic endonasal approaches to the cranial base.

OBJECT: Endoscopic endonasal approaches to the craniovertebral junction (CVJ) and clivus are increasingly performed for ventral skull-base pathology, but the biomechanical implications of these approaches have not been studied. The aim of this study was to investigate the spinal biomechanics of the CVJ after an inferior-third clivectomy and anterior intradural exposure of the foramen magnum as would be performed in an endonasal endoscopic surgical strategy. METHODS: Seven upper-cervical human cadaveric specimens (occiput [Oc]-C2) underwent nondestructive biomechanical flexibility testing during flexion-extension, axial rotation, and lateral bending at Oc-C1 and C1-2. Each specimen was tested intact, after an inferior-third clivectomy, and after ligamentous complex dissection simulating a wide intradural exposure using an anterior approach. Angular range of motion (ROM), lax zone, and stiff zone were determined and compared with the intact state. RESULTS: Modest, but statistically significant, hypermobility was observed after inferior-third clivectomy and intradural exposure during flexion-extension and axial rotation at Oc-C1. Angular ROM increased incrementally between 6% and 12% in flexion-extension and axial rotation. These increases were primarily the result of changes in the lax zone. No significant changes were noted at C1-2. CONCLUSIONS: Inferior-third clivectomy and an intradural exposure to the ventral CVJ and foramen magnum resulted in hypermobility at Oc-C1 during flexion-extension and axial rotation. Although the results were statistically significant, the modest degree of hypermobility observed compared with other well-characterized CVJ injuries suggests that occipitocervical stabilization may be unnecessary for most patients.

Histomorphometric analysis of the temporal bone after change of direction of force vector of mandible: an experimental study in rabbits.

OBJECTIVES: The present study aimed at performing a histological evaluation of the response of temporal bone tissue to a change of direction of the force vector of the mandible in relation to the base of the skull. MATERIAL AND METHODS: Adult rabbits were assigned into four groups with two control and four experimental animals in each group. experimental animals underwent surgery, which resulted in a change of direction of the force vector on the right temporomandibular joint. Samples were collected after 15, 30, 60 and 90 days for histological analysis. RESULTS: In the two-way analysis of variance, the effect of group and time was statistically significant (p<0.001). Additionally, a statistically significant interaction between group and time was observed (p<0.001). Control animals showed normal growth and development of the temporal region. In the experimental group, the change in direction of the force vector of the mandible induced significant changes in the temporal bone, with a bone modeling process, which suggests growth of this cranial structure. CONCLUSIONS: The methodology used in this experiment allows us to conclude that the change in direction of the force vector of the mandible in relation to the skull base induces remodeling and modeling processes in the temporal bone. The resumption of normal oral functions after bone healing of the mandibular fracture appears to increase cell activation in the remodeling and modeling of the temporal bone structure. The observation of areas of temporal bone modeling shows the relevance of further investigation on the correlation between the joint structures and craniofacial growth and development.

Histomorphometric analysis of the temporal bone after change of direction of force vector of mandible: an experimental study in rabbits

OBJECTIVES: The present study aimed at performing a histological evaluation of the response of temporal bone tissue to a change of direction of the force vector of the mandible in relation to the base of the skull. MATERIAL AND METHODS: Adult rabbits were assigned into four groups with two control and four experimental animals in each group. experimental animals underwent surgery, which resulted in a change of direction of the force vector on the right temporomandibular joint. Samples were collected after 15, 30, 60 and 90 days for histological analysis. RESULTS: In the two-way analysis of variance, the effect of group and time was statistically significant (p<0.001). Additionally, a statistically significant interaction between group and time was observed (p<0.001). Control animals showed normal growth and development of the temporal region. In the experimental group, the change in direction of the force vector of the mandible induced significant changes in the temporal bone, with a bone modeling process, which suggests growth of this cranial structure. CONCLUSIONS: The methodology used in this experiment allows us to conclude that the change in direction of the force vector of the mandible in relation to the skull base induces remodeling and modeling processes in the temporal bone. The resumption of normal oral functions after bone healing of the mandibular fracture appears to increase cell activation in the remodeling and modeling of the temporal bone structure. The observation of areas of temporal bone modeling shows the relevance of further investigation on the correlation between the joint structures and craniofacial growth and development.

Strength testing of the human olfactory nerve at the frontal skull base.

Olfactory dysfunction may influence the quality of life tremendously. This study investigated the strength of the human olfactory nerve at the frontal skull base using cadavers. A total of 180 olfactory nerves were examined in 90 human cadaveric heads. The cut edges of the olfactory nerves were pulled until they were pulled out from the skull base. In the first set of 30 cases, each right olfactory nerve was pulled 0° laterally and 0° upward, and each left olfactory nerve was pulled 0° laterally and 15° upward. In the second set of 30 cases, each right olfactory nerve was pulled 0° laterally and 15° upward, and each left olfactory nerve was pulled 15° laterally and 15° upward. In the third set of 30 cases, each right olfactory nerve was pulled 15° laterally and 15° upward, and each left olfactory nerve was pulled 30° laterally and 15° upward. The strength of the olfactory nerve was measured when pulled in each direction. There was no significant difference in the strength of the olfactory nerves when pulling them in the postero-upward direction between 0° and 15° upward. The strengths of the olfactory nerves when pulling them in the postero-lateral direction 0° and 15° laterally were 3.14±1.87 and 4.05±1.70 g (mean ± standard deviation [SD]), respectively; the difference was almost significant. The olfactory nerve could be pulled more laterally than posteriorly because the retraction force is absorbed by the lateral wall of the olfactory fossa.

Do high-speed drills generate high-frequency noise in mastoid surgery?

BACKGROUND: The introduction of increasingly high speed drills for mastoid surgery has heightened the concern that cochlea damage may occur in both the operated and nonoperated ear. It has been observed clinically that this damage could be associated with frequencies above 8,000 Hz and that, to observe these changes, high-frequency audiometry should be performed. Previous studies have investigated noise transmission to the cochlea at frequencies below 4,000 Hz only. There having been, until recently, limitations to the equipment available to measure higher frequencies. OBJECTIVE: To define the characteristics of noise transmitted to the cochlea during drilling of temporal bone, specifically in the higher frequency ranges up to 20,000 Hz. METHODS: Cleaned temporal bones were fitted with 3 mutually perpendicular accelerometers, capable of measuring frequencies in the range 500 to 20,000 Hz. The system was calibrated using a Kamplex Audio Traveller AA220 pure tone audiometer, and accelerometer outputs were recorded on a personal computer at a sampling frequency of 102.4 kHz per channel. The magnitude of the noise transmitted to the cochlea was determined for a range of burrs. RESULTS: Maximum transmission of sound was 108 dBA at 4,000 Hz using a 6.5-mm burr on the cortical mastoid bone. The average results showed that the sound transmission tailed off at the higher frequencies dropping to 84 dBA at 8,000 Hz and 40 dBA at 16,000 Hz. CONCLUSION: The high-frequency hearing reduction noted in patients after mastoid surgery was shown not to be due to excessive high-frequency noise generated by drilling.

Evc works in chondrocytes and osteoblasts to regulate multiple aspects of growth plate development in the appendicular skeleton and cranial base.

Ellis-van Creveld syndrome protein homolog (Evc) was previously shown to mediate expression of Indian hedgehog (Ihh) downstream targets in chondrocytes. Consequently disruption of the Ihh/Pthrp axis was demonstrated in Evc(-/-) mice, but the full extent of Evc involvement in endochondral development was not totally characterized. Herein we have examined further the Evc(-/-) growth plate in a homogeneous genetic background and show that Evc promotes chondrocyte proliferation, chondrocyte hypertrophy and the differentiation of osteoblasts in the perichondrium, hence implicating Evc in both Pthrp-dependent and Pthrp-independent Ihh functions. We also demonstrate that Evc, which localizes to osteoblast primary cilia, mediates Hedgehog (Hh) signaling in the osteoblast lineage. In spite of this, bone collar development is mildly affected in Evc(-/-) mutants. The onset of perichondrial osteoblastogenesis is delayed at the initial stages of endochondral ossification in Evc(-/-) mice, and in later stages, the leading edge of expression of osteoblast markers and Wnt/ß-catenin signaling components is located closer to the primary spongiosa in the Evc(-/-) perichondrium owing to impaired osteoblast differentiation. Additionally we have used Ptch1-LacZ reporter mice to learn about the different types of Hh-responsive cells that are present in the perichondrium of normal and Evc(-/-) mice. Evc mediates Hh target gene expression in inner perichondrial cells, but it is dispensable in the external layers of the perichondrium. Finally, we report cranial base defects in Evc(-/-) mice and reveal that Evc is essential for intrasphenoidal synchondrosis development.

Intraoperative facial nerve motor evoked potential monitoring during skull base surgery predicts long-term facial nerve function outcomes.

OBJECTIVES: This study was designed to clarify whether facial nerve motor evoked potentials (FNMEPs) elicited by transcranial electrical stimulation during skull base surgery are useful for predicting long-term facial nerve function. METHODS: We analyzed FNMEP findings in 35 patients with skull base tumors. Mean follow-up was 24.4 months. Corkscrew electrodes positioned at C3 or C4 and Cz were used to deliver supramaximal stimuli. FNMEPs were recorded from the orbicularis oculi and oris muscles. RESULTS: The correlation between the final-to-baseline FNMEP ratio and initial or long-term facial nerve function was examined. Initial post-operative facial nerve function correlated significantly with the FNMEP ratios in the orbicularis oculi (r = -0.53, P < 0.005) and orbicularis oris (r = -0.80, P < 0.001) muscles. The correlations between FNMEP ratios and facial nerve function remained significant during long-term follow-up (orbicularis oculi muscle: r = -0.43, P < 0.05; orbicularis oris muscle: r = -0.71, P < 0.001). All patients in whom the FNMEP ratio in the orbicularis oculi muscles remained above 50% were assigned to the satisfactory facial nerve function (House-Brackmann Grades i and ii) group at the final examination. DISCUSSION: FNMEP monitoring can predict facial nerve function not only immediately after surgery but also long-term.

Ligaments of the craniocervical junction.

The specialized ligaments of the craniocervical junction must allow for stability yet functional movement. Because injury to these important structures usually results in death or morbidity, the neurosurgeon should possess a thorough understanding of the anatomy and function of these ligaments. To the authors' knowledge, a comprehensive review of these structures is not available in the medical literature. The aim of the current study was to distill the available literature on each of these structures into one offering.

Microsurgical anatomy of Liliequist's membrane demonstrating three-dimensional configuration.

OBJECT: Liliequist's membrane (LM) is an important arachnoid structure in the basal cisterns. The relevant anatomic descriptions of this membrane and how many leaves it has are still controversial. The existing anatomical theories do not satisfy the needs of minimally invasive neurosurgery. We aimed to establish the three-dimensional configuration of LM. METHODS: Fifteen adult formalin-fixed cadaver heads were dissected under a surgical microscope to carefully observe the arachnoid mater in the suprasellar and post-sellar areas and to investigate the arachnoid structure and its surrounding attachments. RESULTS: It was found that the LM actually consists of three types of membranes. The diencephalic membrane (DM) was usually attached by the mesencephalic membrane (MM) from underneath, and above DM it was usually a pair of hypothalamic membranes (HMs) extending superomedially. The pair of HMs was stretched between the DM (or MM) and the hypothalamus and were seldom attached to the carotid-chiasmatic walls between the carotid cistern and the chiasmatic cistern. These three types of membranes (DM, MM, and HM) comprised the main arachnoid structure in the anterior incisural space and often presented as four connected leaves. However, only two thirds of the specimens had all three types of membranes, and there was considerable variation in the characteristics and shapes of the membranes among the specimens. CONCLUSION: All three types of membranes comprising LM serve as important anatomical landmarks and interfaces for surgical procedures in this area.

Evidence for the influence of diet on cranial form and robusticity.

The evolutionary significance of cranial form and robusticity in early Homo has been variously attributed to allometry, encephalization, metabolic factors, locomotor activity, and masticatory forces. However, the influence of such factors is variably understood. To evaluate the effect of masticatory loading on neurocranial form, sibling groups of weanling white rabbits were divided into two cohorts of 10 individuals each and raised on either a soft diet or a hard/tough diet for 16 weeks until subadulthood. Micro-CT was used to quantify and visualize morphological variation between treatment groups. Results reveal trends (P < 0.10) for greater outer table thickness of the frontal bones, zygomatic height, and cranial globularity in rabbits raised on a hard/tough diet. Furthermore, analyses of three-dimensional coordinate landmark data indicate that the basicrania of hard/tough diet rabbits exhibit more robust middle cranial fossae and pterygoid plates, as well as altered overall morphology of the caudal cranial fossa. Thus, long term increases in masticatory loads may result in thickening of the bones of the neurocranial vault and/or altering the curvature of the walls. Differences in cranial regions not directly associated with the generation or resistance of masticatory forces (i.e., frontal bone, basicranium) may be indirectly correlated with diet-induced variation in maxillomandibular morphology. These findings also suggest that long-term variation in masticatory forces associated with differences in dietary properties can contribute to the complex and multifactorial development of neurocranial morphology.

Variability of human foramen magnum size.

The foramen magnum is an important landmark of the skull base and is of particular interest for anthropology, anatomy, forensic medicine, and other medical fields. Despite its importance, few osteometric studies of the foramen magnum have been published so far. A total of 110 transverse and 111 sagittal diameters from Central European male and female dry specimens dating from the Pleistocene to modern times were measured, and related to sex, age, stature, ethnicity, and a possible secular trend. Only a moderate positive correlation between the transverse and the sagittal diameter of the foramen magnum was found. Surprisingly, neither sexual dimorphism, individual age-dependency, nor a secular trend was found for either diameter. Furthermore, the relationship between the individual stature and foramen magnum diameters was weak: thus foramen magnum size cannot be used as reliable indicator for stature estimation. Further consideration of possible factors influencing the variability of human foramen magnum size shall be explored in larger and geographically more diverse samples, thus serving forensic, clinical, anatomical, and anthropological interests in this body part.

Orthodontics in a quantum world II: cranial movement and parafunction.

Maintenance of brain vitality is the most important function of the body. Several oral behaviors are involved in this process. Typical facial characteristics and intra-oral change can result from this. Symptomatically, the response can resemble a temporomandibular joint disorder. An integrative systems approach gives a basis for understanding and treating the condition.

The primate subarcuate fossa and its relationship to the semicircular canals part II: adult interspecific variation.

Studies have reported an empirical link between the size of the semicircular canals and locomotor agility across adult primates. In this paper, we investigate the possibility that this relationship does not follow from the function of the semicircular canals to sense head rotations, but rather reflects spatial constraints imposed by the subarcuate fossa. The latter sits among the three canals and contains the petrosal lobule of the cerebellar paraflocculus, a structure involved in neural processing of locomotion-related eye movements. Hence, it is feasible that agility-related variations of lobule and fossa size affect the arc size of the surrounding semicircular canals. The present study tests such hypothetical correlations by evaluating canal size, fossa size, and agility among extant adult primates. Phylogenetically informed multivariate regression analyses show that, after controlling for body mass, the size of the subarcuate fossa has a significant positive effect on the overall size of the anterior canal and the width of the posterior canal. Multivariate regressions involving the height of the posterior canal and overall size of the lateral canal are not significant. Further bivariate analyses confirm that fossa size is unlikely to play a role in the previously reported link between agility and the size of the posterior and lateral canals. However, fossa size, especially its opening though the arc of the anterior canal, cannot be excluded as a factor that influences the size of the anterior canal more than agility. The findings show that the most reliable functional signals pertaining to locomotion in species that possess a patent subarcuate fossa are likely to come from the lateral canal and are least likely to come from the anterior canal.