Magnetic resonance imaging-based classification of the myodural bridge complex and its influencing factors.

Cerebrospinal fluid (CSF) circulation is considered the third circulation of the human body. Recently, some scholars have proposed the myodural bridge (MDB) as a novel power source for CSF flow. Moreover, the suboccipital muscles can exert a driving force on the CSF via the MDB. This hypothesis is directly supported by head rotation and nodding movements, which can affect CSF circulation. The MDB has been validated as a normal structure in humans and mammals. In addition, the fusion of MDB fibers of different origins that act in concert with each other forms the MDB complex (MDBC). The MDBC may be associated with several CSF disorder-related neurological disorders in clinical practice. Therefore, the morphology of the MDBC and its influencing factors must be determined. In this study, T2-weighted imaging sagittal images of the cervical region were analyzed retrospectively in 1085 patients, and magnetic resonance imaging (MRI) typing of the MDBC was performed according to the imaging features of the MDBC in the posterior atlanto-occipital interspace (PAOiS) and posterior atlanto-axial interspace (PAAiS). The effects of age and age-related degenerative changes in the cervical spine on MRI staging of the MDBC were also determined. The results revealed four MRI types of the MDBC: type A (no MDBC hyposignal shadow connected to the dura mater in either the PAOiS or PAAiS), type B (MDBC hyposignal shadow connected to the dura mater in the PAOiS only), type C (MDBC hyposignal shadow connected to the dura mater in the PAAiS only), and type D (MDBC hyposignal shadow connected to the dura mater in both the PAOiS and PAAiS). The influencing factors for the MDBC typing were age (group), degree of intervertebral space stenosis, dorsal osteophytosis, and degenerative changes in the cervical spine (P < 0.05). With increasing age (10-year interval), the incidence of type B MDBC markedly decreased, whereas that of type A MDBC increased considerably. With the deepening of the degree of intervertebral space stenosis, the incidence of type C MDBC increased significantly, whereas that of type A MDBC decreased. In the presence of dorsal osteophytosis, the incidence of type C and D MDBCs significantly decreased, whereas that of type A increased. In the presence of protrusion of the intervertebral disc, the incidence of type B, C, and D MDBCs increased markedly, whereas that of type A MDBC decreased considerably, with cervical degenerative changes combined with spinal canal stenosis. Moreover, the incidence of both type C and D MDBCs increased, whereas that of type A MDBC decreased. Based on the MRI signal characteristics of the dural side of the MDBC, four types of the MDBC were identified. MDBC typing varies dynamically according to population distribution, depending on age and cervical degeneration (degree of intervertebral space stenosis, vertebral dorsal osteophytosis formation, simple protrusion of intervertebral disc, and cervical degeneration changes combined with spinal canal stenosis, except for the degree of protrusion of the intervertebral disc and the degree of spinal canal stenosis); however, it is not influenced by sex.

Neck circumference as an indicator of Obesity for MetabolicSyndrome in Mexican Healthcare workers

Background: Neck circumference (NC) is a novel anthropometric indicator to assess adiposity in the cervical regionthat is rarely used in Mexico. The greatest advantage of this evaluation is the saving of time, minimal use of instruments, and no pre requisites for patients. Objective: This study aimed to determine the effective-ness of NC as an indicator of obesity for Metabolic Syndrome(MetS) in comparison with BMI and Waist Circumference(WC), and to define NC cutoff levels based on parameters established by the International Diabetes Federation in a groupof healthcare workers from a Public Health Hospital of the State of Morelos, Mexico. Methods: This was a no-randomized, cross-sectional-observational study. Instruments: Anthropometric evaluation and biochemical parameters: lipid profile, fasting glucose, and blood pressure. Statistical analysis: Descriptive, correlational, Poisson multiple regression adjusted by age/sex, and ROC curves using SPSS.23 program. Results: 200 healthcare workers were recruited (146 women and 54 men), age ẋ=42.87, σ=11.25 years. The prevalence of metS was 38% (37% in women and 40.7% in men). BMI, WC, and NC were significantly correlated: BMI and WC (r=.924),BMI and NC (r=.814), and NC and WC (r=.810) (p=.01).Like wise, they were related to hyperglycemia, hypertriglyceridemia, hypertension, and decreased in HDL-cholesterol levels. The NC best cut-off points coupled with two or more components of MetS in women was ≥35.12 cm [AUC=0.765 (95%CI, 0.688-0.843)] and in men ≥41.25 cm [AUC=0.787 (95%CI, 0.688-0.906)]. Conclusion: NC proved to be a reliable indicator that can be quickly and inexpensively evaluated for the determination of obesity for the preliminary diagnosis of MetS (AU)

Imaging of the Craniocervical Junction: A Pictorial Review.

The craniocervical junction (CCJ) is a complex anatomical structure comprising the occiput, the atlas, and the axis. The CCJ plays an important role in maintaining stability, providing protection, and supporting neurovascular structures. The CCJ can be affected by a wide range of congenital variants and traumatic, degenerative, inflammatory, and tumoral pathologies. This pictorial review the normal anatomy of the CCJ and presents the most common anatomical variants and pathologic conditions affecting the CCJ.

An anatomical study of the suboccipital cavernous sinus and its relationship with the myodural bridge complex.

The suboccipital cavernous sinus (SCS) and the myodural bridge complex (MDBC) are both located in the suboccipital region. The SCS is regarded as a route for venous intracranial outflow and is often encountered during surgery. The MDBC consists of the suboccipital muscles, nuchal ligament, and myodural bridge and could be a power source for cerebrospinal fluid circulation. Intracranial pressure depends on intracranial blood volume and the cerebrospinal fluid. Since the SCS and MDBC have similar anatomical locations and functions, the aim of the present study was to reveal the relationships between them and the detailed anatomical characteristics of the SCS. The study involved gross dissection, histological staining, P45 plastination, and three-dimensional visualization techniques. The SCS consists of many small venous sinuses enclosed within a thin fibrous membrane that is strengthened by a fibrous arch closing the vertebral artery groove. The venous vessels are more abundant in the lateral and medial portions of the SCS than the middle portion. The middle and medial portions of the SCS are covered by the MDBC. Type I collagen fibers arranged in parallel and originating from the MDBC terminate on the SCS either directly or indirectly via the fibrous arch. The morphological features of SCS revealed in this research could serve as an anatomical basis for upper neck surgical procedures. There are parallel arrangements of type I collagen fibers between the MDBC and the SCS. The MDBC could change the blood volume in the SCS by pulling its wall during the head movement.

Appropriate neck circumference and waist-to-height ratio cut-off points as predictors of obesity and cardiovascular risk in adolescents.

OBJECTIVE: To determine neck circumference (NC) and waist-to-height ratio (WHtR) cut-off points as predictors of obesity and cardiovascular risk in adolescents. METHODS: Cross-sectional study developed with a subsample of 634 adolescents aged 18 and 19 years belonging to the third phase of the "RPS" cohort (Ribeirão Preto, Pelotas and São Luís) carried out in 2016. The area under the ROC curve (AUC) was identified to assess the predictive capacity of NC and WHtR in relation to the percentage of body fat (%BF), obtained by air displacement plethysmography (ADP), and the cardiovascular risk estimated by the Pathobiological Determinants of Atherosclerosis in Youth (PDAY). RESULTS: The prevalence of obesity by %BF was 7.6% in males and 39.4% in females (p-value <0.001), and the high PDAY risk was 13.8% and 10.9%, respectively. For males, NC cut-off point was 44.0 cm and the AUCs were 0.70 (95%CI 0.58-0.83) to predict obesity and 0.71 (95%CI 0.62-0.80) to predict high cardiovascular risk; for females, NC cut-off point was 40 cm and the AUCs were 0.75 (95%CI 0.69-0.80) and 0.63 (95%CI 0.53-0.73), respectively. WHtR cut-off point was 0.50 for both sexes; for males, the AUCs to predict obesity and high risk according to PDAY were 0.90 (95%CI 0.80-0.99) and 0.73 (95%CI 0.63-0.82), respectively; for females, they were 0.87 (95%CI 0.83-0.90) and 0.55 (95%CI 0.45-0.65), respectively. CONCLUSION: WHtR and NC are good discriminators to assess obesity and cardiovascular risk in adolescents, especially in males.

Quantifying research on anatomical structures, a potential new metric for assessing clinical relevance.

Human anatomy remains an integral part of medical education, and recent studies have documented an emerging consensus on the key anatomical learning objectives for physicians and other health professionals in training, both at the graduate and postgraduate levels. Despite this progress, less attention has been given to assessing the clinical relevance of individual anatomical structures, and which structures students should master to achieve these learning objectives. In this study we hypothesized that published research involving individual anatomical structures is largely driven by the clinical relevance of these structures, and that tabulating the number of such publications can provide an up-to-date, evolving metric of clinical relevance. To test this hypothesis, we developed a semi-automated search routine that uses the PubMed database to quantify the publication frequency of anatomical structures and compared that to a previous study that assessed the importance of structures of the head and neck using the Delphi method, a formal procedure of generating expert consensus. Using our new approach, we were able to rank the research intensity of 2182 anatomical structures included in Grant's Dissector, a widely used textbook for anatomical dissection. Furthermore, a sample of these PubMed-derived ranks had a highly significant, positive correlation with ranks derived from a consensus of experts. Similar results were obtained when PubMed searches were restricted to journals that focus on applying knowledge in a clinical setting. Our study provides a potential new tool for anatomical educators who are aligning their basic science curricula with the clinical knowledge expected of medical graduates.

The Short Neck: Challenges and Techniques.

Establishing a pleasant cervical contour in short-neck patients is of one the most difficult challenges for a facial plastic surgeon. Subplatysmal volume reduction, platysma tightening, and skin distribution adequately coupled with the middle third facelift are the pillars of the surgical approach. Additionally, treating the small chin, which is frequently observed in these patients, improves the overall result. In this paper, an objective method to define short-neck patients is offered. The applied surgical anatomy of the neck is revised. Innovative strategies to treat the supra and infrahyoid subplatysmal structures are presented, including the sternohyoid muscles plicature and the use of the interplatysmal/subplatysmal fat flap. A novel chin augmentation technique, using a subperiosteal en bloc fat graft is also introduced. A modified deep plane approach is described, including a continuous suture of the middle third fasciocutaneous flap. A combined lateral platysma tensioning with the sternocleidomastoid rejuvenation is demonstrated. Lastly, the hemostatic net is revisited as a critical approach to resolve the defying skin accommodation.

Anatomy of Neck Muscles, Spaces, and Lymph Nodes.

The following article details the muscular anatomy of the head and neck, including insertion, origin, action and innervation, organized by anatomic subunit and/or major action. This article also describes the spaces of the head and neck, including boundaties and contents. Finally, cervical lymph nodes are addressed according to anatomic location and lymphatic drainage.

Root of the Neck and Extracranial Vessel Anatomy.

The root of the neck is the junctional anatomic structure between the thoracic inlet, the axilla, and the lower neck. The detailed radiological anatomy of this critical area is discussed in this review.

Cranial ecomorphology of turtles and neck retraction as a possible trigger of ecological diversification.

Turtles have a highly modified body plan, including a rigid shell that constrains postcranial anatomy. Skull morphology and neck mobility may therefore be key to ecological specialization in turtles. However, the ecological signal of turtle skull morphologies has not been rigorously evaluated, leaving uncertainties about the roles of ecological adaptation and convergence. We evaluate turtle cranial ecomorphology using three-dimensional geometric morphometrics and phylogenetic comparative methods. Skull shape correlates with allometry, neck retraction capability, and different aquatic feeding ecologies. We find that ecological variables influence skull shape only, whereas a key functional variable (the capacity for neck retraction) influences both shape and size. Ecology and functional predictions from three-dimensional shape are validated by high success rates for extant species, outperforming previous two-dimensional approaches. We use this to infer ecological and functional traits of extinct species. Neck retraction evolved among crownward stem-turtles by the Late Jurassic, signaling functional decoupling of the skull and neck from the shell, possibly linked to a major episode of ecomorphological diversification. We also find strong evidence for convergent ecological adaptations among marine groups. This includes parallel loss of neck retraction, evidence for active hunting, possible grazing, and suction feeding in extinct marine groups. Our large-scale assessment of dietary and functional adaptation throughout turtle evolution reveals the timing and origin of their distinct ecomorphologies, and highlights the potential for ecology and function to have distinct effects on skull form.

Tartarugas tem um plano corpóreo bastante modificado, que inclui um casco rígido que restringe sua anatomia pós-craniana. Portanto, a morfologia craniana e a mobilidade do pescoço devem ser centrais nas especializações ecológicas de tartarugas. No entanto, o sinal ecológico das diferentes morfologias de crânio de tartarugas não foi ainda rigorosamente avaliado, deixando incertezas sobre os papéis de adaptações ecológicas e convergência. Avaliamos a ecomorfologia craniana de tartarugas utilizando morfometria geométrica tridimensional e métodos filogenéticos comparativos. A forma craniana correlaciona com alometria, capacidade de retração do pescoço e diferentes ecologias alimentares aquáticas. Encontramos que variáveis ecológicas influenciam apenas a forma do crânio, enquanto uma importante variável funcional (a capacidade de retração do pescoço) influencia tanto a forma como o tamanho do crânio. Predições ecológicas e funcionais para espécies viventes a partir de formas tridimensionais são validadas com altas taxas de sucesso, superando abordagens bidimensionais. Utilizamos isso para inferir traços ecológicos e funcionais de espécies extintas. A retração do pescoço evoluiu em linhagens extintas mais próximas à origem do grupo-coronal durante o Jurássico Final, indicando uma dissociação funcional entre crânio e pescoço do casco, algo possivelmente ligado a um importante episódio de diversificação ecomorfológica. Também encontramos forte evidência para adaptações ecológicas convergentes em grupos marinhos. Isso inclui a perda paralela da retração do pescoço, evidência de caça ativa, alimentação por sucção, além de possível preferência por plantas aquáticas em grupos marinhos extintos. Nosso estudo de larga-escala sobre adaptações funcionais e relacionadas à dieta ao longo da evolução de tartarugas revela o tempo e origem de suas distintas ecomorfologias, e destaca ainda o potencial de ecologia e função terem efeitos distintos sobre a forma craniana.

Application of the new 'XU-line' in the dynamic ultrasonographic evaluation of the spatial displacement of anterior cervical tissues for airway management: protocol for a prospective observational study.

INTRODUCTION: Patients with cervical spondylosis have a high incidence of difficult airway, and unpredicted difficult intubation may be life-threatening. Traditional predictors and imaging data may suggest a difficult airway, but these data have limited predictive value, with low sensitivity and specificity. Ultrasonography is a non-irradiating, reproducible, inexpensive and simple tool that provides good imaging of the cervical soft tissue for airway assessment. This study will use the new 'XU-line' in the dynamic ultrasonographic airway evaluation of the spatial displacement of the anterior cervical tissues to determine whether preoperative ultrasonographic assessment of the neck anatomy can predict difficult airway. METHODS AND ANALYSIS: This prospective, observational study will be conducted in a single centre. Four hundred and eleven patients scheduled for anterior cervical decompression and fusion under general anaesthesia will be recruited. The parallel trunk reference line through the mentum is defined as the XU-line, and the spatial displacement of the anterior cervical soft tissue relative to the XU-line at six anatomical levels in the transverse plane and two distances in the sagittal plane will be measured on ultrasonography with the patient in the supine position and the sniff position. The spatial displacement distances of soft tissue structures relative to the XU-line will be compared between the 'easy intubation' and 'difficult intubation' groups (in accordance with the Cormack-Lehane classification). Receiver operating characteristic curves will be used to determine the sensitivity and specificity of the 'difficulty prediction capability' of each ultrasonographic and physical measurement. Multiple logistic regression analysis will be performed to determine the independent predictors of difficult intubation. ETHICS AND DISSEMINATION: Ethical approval for this study has been obtained from the Peking University Third Hospital Medical Science Research Ethics Committee. The results of this study will be disseminated via a peer-reviewed publication and national and international conferences and workshops. TRIAL REGISTRATION NUMBER: ChiCTR2000034446.

Sexual selection promotes giraffoid head-neck evolution and ecological adaptation.

The long neck of the giraffe has been held as a classic example of adaptive evolution since Darwin's time. Here we report on an unusual fossil giraffoid, Discokeryx xiezhi, from the early Miocene, which has an unusual disk-shaped headgear and the most complicated head-neck joints in known mammals. The distinctive morphology and our finite element analyses indicate an adaptation for fierce head-butting behavior. Tooth enamel isotope data suggest that D. xiezhi occupied a niche different from that of other herbivores, comparable to the characteristic high-level browsing niche of modern giraffes. The study shows that giraffoids exhibit a higher headgear diversity than other ruminants and that living in specific ecological niches may have fostered various intraspecific combat behaviors that resulted in extreme head-neck morphologies in different giraffoid lineages.

A new concept of the fiber composition of cervical spinal dura mater: an investigation utilizing the P45 sheet plastination technique.

PURPOSE: Few reports have been published regarding the microanatomy of the dura mater located at the craniovertebral junction (CVJ). In clinic, the precise microanatomy of the CVJ dura mater would be taken into account, for reducing surgical complications and ineffective surgical outcomes. The main objective of the present investigation was to further elucidate the fiber composition and sources of the cervical spinal dura mater. METHODS: The formalin-fixed adult head and neck specimens (n = 21) were obtained and P45 plastinated section method was utilized for the present study. The fibers of the upper cervical spinal dura mater (SDM) were examined in the P45 sagittal sections in the CVJ area. All photographic documentation was performed via a Canon EOS 7D Mark camera. RESULTS: The posterior wall of the SDM sac at CVJ was found to be composed of stratified fibers, which are derived from three sources: the cerebral dura mater, the occipital periosteum, and the myodural bridge (MDB). The proper layer of the cerebral dura mater passes over the brim of the foramen magnum and enters the vertebral canal to form the inner layer of the SDM, and the fibers originating from the periosteum of the brim of the foramen magnum form the middle layer. The fibers of the MDB are inserted into the SDM and form its outer layer. It was found that the total number of fibers from each origin varied in humans. CONCLUSION: At the CVJ, the posterior wall of the SDM is a multi-layered structure composed of three different originated fibers. The cerebral dura mater, the periosteum located at the brim of the foramen magnum, and MDB contribute to the formation of the SDM. The present study would be beneficial to the choice of surgical approach at the CVJ and the protection of the SDB.

Head and Neck Characteristics as Risk Factors For and Protective Factors Against Mild Traumatic Brain Injury in Military and Sporting Populations: A Systematic Review.

BACKGROUND: Investigators have proposed that various physical head and neck characteristics, such as neck strength and head and neck size, are associated with protection from mild traumatic brain injury (mTBI/concussion). OBJECTIVES: To systematically review the literature and investigate potential relationships between physical head and neck characteristics and mTBI risk in athletic and military populations. METHODS: A comprehensive search of seven databases was conducted: MEDLINE, EMBASE, CINAHL, Scopus, SPORTDiscus, Cochrane Library, and Web of Science. Potential studies were systematically screened and reviewed. Studies on military and athletic cohorts were included if they assessed the relationship between physical head-neck characteristics and mTBI risk or proxy risk measures such as head impact kinematics. RESULTS: The systematic search yielded a total of 11,723 original records. From these, 22 studies met our inclusion criteria (10 longitudinal, 12 cross-sectional). Relevant to our PECO (Population, Exposure, Comparator, and Outcomes) question, exposures included mTBI incidence and head impact kinematics (acceleration, velocity, displacement) for impacts during sport play and training and in controlled laboratory conditions. Outcome characteristics included head and neck size (circumference, mass, length, ratios between these measures), neck strength and endurance, and rate of force development of neck muscles. DISCUSSION: We found mixed evidence for head and neck characteristics acting as risk factors for and protective factors against mTBI and increased susceptibility to head impacts. Head-neck strength and size variables were at times associated with protection against mTBI incidence and reduced impact kinematics (14/22 studies found one or more head-neck variable to be associated with protection); however, some studies did not find these relationships (8/22 studies found no significant associations or relationships). Interestingly, two studies found stronger and larger athletes were more at risk of sustaining high impacts during sport. Strength and size metrics may have some predictive power, but impact mitigation seems to be influenced by many other variables, such as behaviour, sex, and impact anticipation. A meta-analysis could not be performed due to heterogeneity in study design and reporting. CONCLUSION: There is mixed evidence in the literature for the protective capacity of head and neck characteristics. We suggest field-based mTBI research in the future should include more dynamic anthropometric metrics, such as neck stiffness and response to perturbation. In addition, laboratory-based mTBI studies should aim to standardise design and reporting to help further uncover these complicated relationships.

Normal Vascular Structures and Variants on Head and Neck Imaging.

The vasculature of the neck, comprised of arteries and veins, provides for the supply and return of blood to and from the brain, and to structures of the neck and face. Knowledge of normal appearance and anatomy, and anatomic variants, may help one distinguish between normal and pathologic processes in the neck, which may affect diagnosis or choice of surgical approach. Other related structures that are important to recognize include the thoracic duct and carotid body. In this article examples of mostly computed tomography and MR imaging of normal anatomy and some of these variants are shown.

Are clinical medical students confident about their head and neck anatomy knowledge?

Anatomy is a pillar of medical knowledge and essential for safe medical and surgical practice. The literature highlights concerns regarding anatomy knowledge, and knowledge of the head and neck in particular, in medical students and newly qualified doctors. We investigated medical students' confidence to be assessed on head and neck anatomy, the amount of teaching they received, and its mode of delivery, through an online survey completed by 185 medical students across two English Universities (122 (66%) students from University A and 63 (34%) from University B). Students were in their third to fifth year of medical school. A total of 126 (68%) had received two to four sessions on head and neck anatomy, and 56 (30%) had received one or two sessions. A total of 113 (61%) had received prosection teaching, and 44 (24%) had received computer/virtual anatomy teaching. In total, 140 (76%) did not feel confident to be assessed on head and neck anatomy, and 137 (74%) did not feel they had received an adequate amount of head and neck anatomy teaching. Despite formal head and neck anatomy teaching most of our cohort did not feel confident to be assessed on the topic. Further work is required to integrate anatomy into the clinical years and to devise a national undergraduate curriculum to enhance an interest in head and surgery as a career.