The cranio-cervical junction (CCJ) represents a critical transitional zone between the cranium and cervical spine. It is speculated that changes of tissue compliance within the CCJ may disrupt normal cerebrospinal fluid (CSF) flow, but this hypothesis has not been sufficiently validated. Therefore, this research study investigated the influence of tissue compliance changes at the CCJ on CSF dynamics and its potential role in related neurological disorders. A collagen fibrous hyperplasia model was established by injecting bleomycin (BLM) into the posterior atlanto-occipital interspace (PAOiS) in mice. After four weeks, the soft tissues of the PAOiS were harvested for histological and molecular analyses to verify the successful establishment of the animal model. A biomechanical investigation was performed to assess tissue compliance in the PAOiS. CSF pressure in the lateral ventricle was monitored to evaluate the influence of the tissue compliance changes on CSF dynamics. After BLM treatment, the deposition of collagen fibers and the expression levels of Col Iα1 and α-SMA in the PAOiS were significantly increased, which indicated that collagen fibrous hyperplasia model in mice was successfully established. Uniaxial tensile testing results revealed a significant increase of the elastic modulus in the PAOiS, indicating enhanced stiffness and reduced compliance of the PAOiS tissue. Furthermore, CSF pressure in the lateral ventricle was elevated following these changes in the PAOiS tissue. This study demonstrated that reduced tissue compliance caused by hyperplasia can disrupt normal CSF dynamics, offering new insights into the pathogenesis of neurological disorders associated with CSF dynamics.

The ligamentum flavum (LF) is a passive stabilizing tissue that connects two adjacent vertebral arches and contributes to the enclosure the spinal canal, thereby closing the entire canal posteriorly. However, a gap exists at the posterior atlanto-occipital and atlanto-axial interspaces, where the LF is absent and replaced by the myodural bridge (MDB), which attaches to the spinal dura mater. The reasons for this anatomical difference and how it arises during development remain unclear. There are notable structural differences between MDB and LF. The MDB consists primarily of type I collagen fibers, while the LF contains both collagen and elastin fibers, with the latter comprising a higher proportion. This study speculates that LOX and LOXL1, as key regulators of fiber synthesis, play an essential role in the development of MDB and LF. Differences in the expression of LOX and LOXL1, which are involved in collagen and elastin cross-linking, may be one of the main factors underlying this structural divergence in the posterior cervical interspace. This study examined the cervicooccipital regions of rat embryos and young rats using histology, immunohistochemistry, and RT-qPCR to compare morphological and developmental differences between the MDB and LF. Additional experiments using the BAPN inhibitor were conducted to investigate the expression patterns and functional differences of LOX and LOXL1 during the development of the MDB and LF. Our aim is to clarify the developmental processes of the MDB and LF, identify the causes of structural differences in the posterior cervical interspaces, and reveal the molecular mechanisms regulating their formation. The conclusion of the current study as follows: ①The MDB and LF exhibit distinct histological developmental patterns: cells and fibers in the MDB align in an organized manner later than those in the LF, while the MDB forms its complete structures earlier than the LF. ②LOX and LOXL1 play critical roles in collagen and elastic fibers formation, mediating fiber synthesis in both the MDB and LF. ③Differential expression of LOX and LOXL1 during development leads to variations in fiber composition and maturation timing between the MDB and LF, contributing to their structural differences in the posterior cervical spinal interspace.

The myodural bridge complex (MDBC) is a phylogenetically conserved composite anatomical structure that anchors the suboccipital musculature and nuchal ligament to the spinal dura mater (SDM) at the cranio-cervical junction, with species-specific morphological adaptations across vertebrates. Physiological functions of the MDBC include hypothesized mediation of cerebrospinal fluid (CSF) circulation dynamics, stabilizing the SDM during head movements to prevent dural folding, and transmitting proprioceptive signals from suboccipital musculature to the central nervous system. Clinical evidence increasingly links MDBC pathological alterations to a spectrum of cranio-cervical disorders, such as chronic cervicogenic headaches, Chiari malformation Type I, cervicogenic dizziness, and Ehlers-Danlos syndrome-associated symptoms. A comprehensive understanding of MDBC structure and function is critical to unraveling its putative mechanistic role in CSF homeostasis and cranio-cervical biomechanics, thereby providing novel insights for the diagnosis and management of related neurological conditions. This review systematically summarizes current knowledge of the MDBC in terms of its morphology, physiology, developmental biology and pathology.

Recent research in Parkinson’s disease (PD) has increasingly focused on alterations in cerebrospinal fluid (CSF) dynamics and glymphatic system (GS) function. The myodural bridge (MDB), a structure connecting the suboccipital muscles to the spinal dura mater, is involved in the regulation of CSF dynamics. The rectus capitis posterior minor (RCPmi) is a core component of the myodural bridge complex (MDBC). This study employed magnetic resonance imaging (MRI) to evaluate morphological changes in the RCPmi in PD patients and to explore their potential association with CSF dynamics and disease duration. This retrospective MRI study included 349 participants: 156 patients with PD and 193 healthy controls (HC). The occiput-C2 angle (OC2A) was measured on mid-sagittal T2-weighted images. Standardized cross-sectional area (CSA) ratios of MDBC constituent muscles (RCPmi, RCPma, OCI) and non-constituent muscles (OCS, RCL) were quantified on axial images. In 51 PD patients with complete disease duration records (range 1–14 years), the correlation between RCPmi CSA and disease duration was analyzed. From the overall cohort, 277 participants with well-defined occipito-atlantal cistern (OAC) morphology (114 PD, 163 HC) were selected for measurement of OAC parameters (D-FM, D-C1, D-C2) and concurrent anteroposterior diameters of the medulla oblongata and upper cervical spinal cord at the corresponding anatomical levels. No significant differences were observed between the PD and HC groups in OC2A or atlas posterior arch CSA (P > 0.05), indicating that subsequent muscle comparisons were not biased by head position or individual anatomical variation. Compared with the HC group, the PD group exhibited significantly larger CSAs of all MDBC constituent muscles (P < 0.05), with the most pronounced difference noted for RCPmi (PD: 1.97 ± 1.35 vs. HC: 1.58 ± 1.07, P = 0.003). No significant differences were found for non-constituent muscles (P > 0.05). Within the PD group, RCPmi CSA showed a moderate positive correlation with disease duration (r = 0.47, P < 0.001). Analysis of OAC parameters revealed significantly larger D-C1 and D-C2 distances in the PD group compared with the HC group (D-C1: 3.96 ± 1.29 mm vs. 3.60 ± 1.29 mm, P = 0.020; D-C2: 2.75 ± 0.88 mm vs. 2.45 ± 0.82 mm, P = 0.004), whereas D-FM did not differ significantly (P > 0.05). Concurrent measurements of neural tissue anteroposterior diameters at the same anatomical levels as the OAC parameters showed no significant differences between PD group and HC group (P > 0.05). This study demonstrates selective hypertrophy of the RCPmi in patients with PD, with the degree of hypertrophy significantly correlated with both disease duration and OAC enlargement. These morphological findings provide a cross‑sectional imaging correlate of disease chronicity. The study did not directly measure CSF dynamics or longitudinal disease progression; therefore, any link between RCPmi hypertrophy and CSF function remains hypothetical and requires future functional and longitudinal validation.

BACKGROUND:The medial patellofemoral ligament (MPFL) is the most important passive restraint of the medial patella and provides approximately 53% to 80% of medial soft-tissue restraints, although its relationship to the parapatellar structures is still not completely understood. METHODS:Twenty-six formalin-fixed knees (13 for P45 plastination, 10 for dissection, and 3 for histology) were obtained from cadavers donated to the Department of Anatomy at Dalian Medical University. The mean age of the donors was 78.1 years (range, 52 to 95 years). These specimens were obtained from 4 women and 10 men. The integration of the anterior end of the MPFL with the extensor apparatus of the knee was observed, and the morphological observations were captured using a digital camera. RESULTS:The MPFL was found to be attached to the extensor apparatus in 3 ways: its main fibers ran deep to the vastus medialis obliquus (VMO) tendon and ultimately inserted into it; its upper portion extended from, and was reinforced by, the vastus intermedius (VI) tendon; and its lower portion merged weakly into the parapatellar tendon. No direct attachment to the patella was found. CONCLUSIONS:The MPFL attachments to the extensor apparatus occur in 3 locations: the VMO tendon, the VI tendon, and the parapatellar tendon-and not the patella. No direct attachment to that bone was identified. This study provides a comprehensive anatomical relationship between the MPFL and the extensor apparatus of the knee (the patella and quadriceps). Clinically, we suggest that reconstruction of the MPFL be performed with fixation of its anterior end to the VMO rather than to the patella.

The myodural bridge (MDB) was described as a dense fibrous tissue connecting the suboccipital musculature with the spinal dura mater. Now, the concept of the MDB was perceived as an exact anatomical structure likely essential for cerebrospinal fluid (CSF) circulation. The MDB has been shown to be universal across mammals, reptiles, and birds. To determine the existence of the MDB in other vertebrates on morphological study, representatives in amphibians and bony fishes were examined. It was found that the dense fibrous tissue connected the interarcuales muscle (IAR) and the spinal dura mater in the Xenopus laevis. In four examined fish species, somatic muscle fibers were directly anchored to the vertebral canal membrane. This observation led to the hypothesis that, during movement, these muscles may exert a pulling force on the membrane, generating negative pressure. It is speculated that this may serve as the driving force for CSF circulation. Thus, this connection suggests a functional similarity to the MDB observed in other vertebrate species. Based on this finding, the study proposes the MDB as a functionally analogous structure with a universal existence in amphibians and bony fishes.

Chiari malformation type I (CM-I) is the most common subtype of Chiari malformation which can lead to brainstem compression and alterations in cerebrospinal fluid (CSF) flow. Common complications in patients undergoing traditional surgical approach include pseudomeningocele, CSF leak, and exacerbation of symptoms. The authors present a new minimally invasive surgery technique for protection and strengthening of the myodural bridge (MDB) in order to prevent the postoperative complications. A retrospective study was performed on 55 CM-I patients undergoing surgical treatment from January 2019 to April 2024 in a center. These patients underwent the surgical procedure of either posterior fossa decompression with duraplasty and tonsillar coagulation (PFDDC) or PFDDC with protection and strengthening of the MDB (PFDDC + MDB). The clinical outcomes and complications of the two procedures. 29 patients underwent PFDDC, and 26 patients underwent PFDDC + MDB. Overall complications rates were significantly reduced in the PFDDC + MDB group (3.8% vs. 34.5%, P = 0.012). Meningitis was observed in 3 (10.3%) in the PFDDC group and 1 (3.8%) in the PFDDC + MDB group (P = 0.613). Pseudomeningocele was more frequent in the PFDDC group than in the PFDDC + MDB group (24.1% vs. 0%, P = 0.011). No patient required a revision operation. There were no statistical differences in symptom improvement between the two groups. PFDDC + MDB seems to be a safe and effective treatment for CM-I patients with or without syringomyelia. This new procedure can bring clinical improvement and lower complication rates.

Background:The medial patellofemoral ligament (MPFL) is the most important passive restraint of the medial patella and provides approximately 53% to 80% of medial soft-tissue restraints, although its relationship to the parapatellar structures is still not completely understood.Methods:Twenty-six formalin-fixed knees (13 for P45 plastination, 10 for dissection, and 3 for histology) were obtained from cadavers donated to the Department of Anatomy at Dalian Medical University. The mean age of the donors was 78.1 years (range, 52 to 95 years). These specimens were obtained from 4 women and 10 men. The integration of the anterior end of the MPFL with the extensor apparatus of the knee was observed, and the morphological observations were captured using a digital camera.Results:The MPFL was found to be attached to the extensor apparatus in 3 ways: its main fibers ran deep to the vastus medialis obliquus (VMO) tendon and ultimately inserted into it; its upper portion extended from, and was reinforced by, the vastus intermedius (VI) tendon; and its lower portion merged weakly into the parapatellar tendon. No direct attachment to the patella was found.Conclusions:The MPFL attachments to the extensor apparatus occur in 3 locations: the VMO tendon, the VI tendon, and the parapatellar tendon-and not the patella. No direct attachment to that bone was identified. This study provides a comprehensive anatomical relationship between the MPFL and the extensor apparatus of the knee (the patella and quadriceps). Clinically, we suggest that reconstruction of the MPFL be performed with fixation of its anterior end to the VMO rather than to the patella.

Objective To classify myodural bridge complex (MDBC) in the posterior atlanto-occipital interspace (PAOiS) and posterior atlanto-axial interspace (PAAiS) in cervical spondylotic myelopathy (CSM) based on Magnetic Resonance Imaging (MRI), analyzing the effects of sex, age, spinal compression ratio(CR), space available for the cord༈SAC༉, and cervical sagittal balance༈CSB) parameters on the classification of MDBC in CSM, the aim is to provide imaging evidence for the functional research and clinical application of MDBC. Methods Imaging data from 96 patients with CSM and 104 healthy adults were retrospectively selected, were evaluated by univariate analysis of factors and multi-factor analysis of factor Influencing the MRI Classification of MDBC in CSM . Results The results showed significantly lower proportions of Type A and Type B MDBC in the CSM group than in the control group (P < 0.001), the proportions of type C and type D MDBC were greater than those in the control group (P < 0.05), and have a statistically significant correlation with age (P < 0.05), but not with sex (P > 0.05). Types C and D predominated in the MDBC classification in CSM, regardless of sex and age (P > 0.05). Parameters such as the mean subaxial cervical space available for the cord (MSCSAC), and mean subaxial cervical compression ration (MSCCR) significantly influenced the MDBC classification in CSM (P < 0.05), particularly for Types C and D. Sex and CSB did not affect MDBC classification. Conclusion The MDBC classification in CSM predominantly showed Type C and Type D, regardless of age. MSCSAC and MSCCR are influencing factors of MDBC classification in CSM, particularly affecting Type C and Type D MDB, regardless of sex and CSB.

Clinical studies have shown that there may be a certain relationship between pathological changes of the myodural bridge complex (MDBC) and chronic headaches of unknown cause. But there is still a lack of experimental evidence to explain the possible mechanism. This study aims to further confirm this relationship between MDBC and chronic headaches and explore its potential occurrence mechanism in rats. Bleomycin (BLM) or phosphate-buffered saline (PBS) was injected into the myodural bridge fibers of rats to establish the hyperplastic model of MDBC. After 4 weeks, the occurrence of headaches in rats was evaluated through behavioral scores. The immunohistochemistry staining method was applied to observe the expression levels of headache-related neurotransmitters in the brain. Masson trichrome staining results showed that the number of collagen fibers of MDBC was increased in the BLM group compared to those of the other two groups. It revealed hyperplastic changes of MDBC. The behavioral scores of the BLM group were significantly higher than those of the PBS group and the blank control group. Meanwhile, expression levels of CGRP and 5-HT in the headache-related nuclei of the brain were increased in the BLM group. The current study further confirms the view that there is a relationship between pathological changes of MDBC and chronic headaches of unknown cause. This study may provide anatomical and physiological explanations for the pathogenesis of some chronic headaches of unknown cause.

A Study on Relationship between Single-Slice Hounsfield Unit(HU) value of the Chinese proximal humerus and Bone Mineral Density(BMD) Using Routine Chest CT and Dual-energy X-ray Absorptiometry(DEXA) was performed. Data were collected from 240 individuals who underwent DEXA and routine chest CT scans (including full images of the proximal humerus) on the samet 967 day a Hospitals between January 2019 and December 2021. The method of measuring single-slice HU values of the proximal humerus ontine rou chest CT scans exhibited high reliability and repeatability (intraclass correlation coefficient > 0.961, P < 0.001). A strongositive pcorrelation was observed between single-slice HU values of the proximal humerus and DEXA results, with the 20-mm HU value demonstratinghighest the correlation. Across different BMI groups, the Area Under Curve (AUC) for the 20-mm HU value was consistently the largest (AUC=0.701- 0.813, P< 0.05). Therefore, the 20-mm HU value can be considered a reliable reference for the opportunistic screening ofD, lo with BM reference values of -4HU for underweight individuals, -13HU for normal weight individuals, -7HU for overweight individuals,-16HU and for obese individuals. Values below these thresholds indicate a risk of low BMD. This study enriches the Chinese BMD data ands a offer swift and effective approach for opportunistically screening low BMD.

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.

目的 人肌硬膜桥为枕下头后小直肌、头后大直肌、头下斜肌及项韧带等与硬脊膜之间的致密纤维连接结构,具有重要的生理作用及临床意义.已有研究提出肌硬膜桥可能与脑脊液循环和慢性颈源性头痛有关.目前研究发现,哺乳动物中普遍存在肌硬膜桥这一结构,并且鸟类中的家鸡、岩鸽,爬行纲中的暹罗鳄、巴西龟都存在肌硬膜桥样结构.为进一步分析肌硬膜桥在不同纲目的结构形态差异,为其功能研究提供基础.本次研究以爬行纲蜥蜴目中最常见的丽纹攀蜥为实验对象,补充爬行纲肌硬膜桥的形态特点.方法 采用大体解剖、厚断层切片、组织学切片染色等方法,对20只丽纹攀蜥的枕后区结构特点及肌硬膜桥样结构的存在情况进行观察.结果 丽纹攀蜥枕后肌由融合的头背大直肌、头背小直肌、头前斜肌(我们定义为头背直肌)及头后斜肌构成.于寰枕间隙内,自头背直肌腹侧发出的片状致密纤维连接组织向腹侧走行,与硬脊膜紧密相连.于寰枢间隙内,自头后斜肌腹侧发出的致密纤维连接组织向腹侧走行,与硬脊膜紧密相连.且此致密纤维连接结构为具有极强双折光性的Ⅰ型胶原纤维.结论 丽纹攀蜥的头背直肌、头后斜肌与硬脊膜之间存在致密的纤维连接结构,即肌硬膜桥样结构.此结构可能与丽纹攀蜥头颈部的活动密切相关,发挥与人类肌硬膜桥相似的生理功能.

The myodural bridge is a dense connective tissue connecting muscles and ligaments to the spinal dura mater in the atlanto-occipital interspace. Some researchers believe that the myodural bridge may play a vital physiological role. It is possible, for instance, that the prevention of spinal dura mater infoldings might be involved in regulated cerebrospinal fluid circulation. For instance, it is possible to prevent spinal dura mater infoldings, regulating cerebrospinal circulation. Bats are nocturnal and the only mammals that can perform a genuine and sustained flight, whereas tree shrews are arboreal mammals that often climb to a high altitude of about 10,000 feet. Both animals have lifestyles that are different from other previously studied mammals. The study of these two animals will shed further light on the existence of the myodural bridge in mammals. Gross anatomical dissection was used to observe the connections between the deep muscles of the neck and the dura mater at the level of the atlanto-occipital interspace. The existing structures were analyzed using conventional and special histological staining techniques. The suboccipital regions in bats and tree shrews contained the rectus capitis dorsal major (RCDma), rectus capitis dorsal minor (RCDmi), oblique capitis anterior (OCA), and oblique capitis posterior (OCP). Dense connective tissue connects the RCDmi to the posterior atlanto-occipital membrane (PAOM) and the latter to the spinal dura mater. The myodural bridge in these mammals shares a similar structure to the myodural bridge in humans. Histological analyses confirmed that the connective fibers of the myodural bridge were primarily type I collagen fibers. In this study, it is supplemented by the existence of the myodural bridge in mammals. This further demonstrates that myodural bridge widely exists in the normal anatomy of mammals. This provides morphological support for a comparative anatomical study of the physiological function of the myodural bridge.

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.

The myodural bridge complex (MDBC) is described as a functional anatomic structure that involves the dense connective tissue fibers, muscles, and ligaments in the suboccipital region. It has recently been proposed that the MDBC can influence cerebrospinal fluid (CSF) circulation. In the present study, bleomycin (BLM), a type of antibiotic that is poisonous to cells, was injected into the posterior atlanto-occipital interspace (PAOiS) of rats to induce fibrous hyperplasia of structures in PAOiS. Sagittal sections of tissues obtained from the posterior-occipital region of the rats were stained utilizing the Masson Trichrome staining method. Semiquantitative analysis evidenced that the collagen volume fraction of collagen fibers of the MDBC, as well as the sum of the area of the spinal dura mater and the posterior atlanto-occipital membrane in the BLM group were significantly increased (p < .05) compared to that of the other groups. This finding illustrates that the MDBC fibers as well as other tissues in the PAOiS of rats in the BLM group developed fibrotic changes which reduced compliance of the spinal dura mater. Indeed, the sectional area of the rectus capitis dorsal minor muscle in the BLM group was measured to be increased. These changes may further restrict CSF flow. The present research provides support for the recent hypothesis proposed by Labuda et al. concerning the pathophysiology observed in symptomatic adult Chiari malformation Type I patients, that there exists a relationship between the altered compliance of the anatomic structures within the craniocervical region and the resultant compensatory hyperplasia of the MDBC.

A comparative study of the morphology of suboccipital cavernous sinus (SCS) using MRI and cast specimens was performed. The present retrospective study analysed the craniocervical magnetic resonance venography (MRV) imaging data of 61 patients. Three-dimensional reconstruction was performed using Mimics 19.0. The SCS left-right diameter(d1), distance from the midline (d2), supero-inferior diameter(d3), anteroposterior diameter (d4), distance from posterior diameter to skin (d5), and diameter of the SCS at different parts (d6-d8) were measured. Comparison between MRV images and cast specimens, the SCS, marginal sinus, anterior condylar vein, and vertebral artery venous plexus were symmetrical and could be bilaterally displayed, whereas the presence of extra condylar vein and posterior condylar vein exhibited different types. The adjacency between the SCS and its communicating vessels and changes in its communicating vessels corresponded well with the MRV images and cast specimens. Many types of the presence of left and right lateral condylar and posterior condylar veins were found in the cast specimens, which could be divided into the bilateral presence of posterior condylar and lateral condylar veins, unilateral presence of posterior condylar veins, and unilateral presence of lateral condylar vein. A total of 61 cases analysed using MRV images revealed the bilateral presence of posterior condylar and lateral condylar veins (77.1 %), the unilateral presence of posterior condylar vein (18.0 %), and the unilateral presence of lateral condylar vein (9.8 %), of which the bilateral presence of posterior condylar and lateral condylar veins accounted for the largest proportion. MRV images and cast specimens of the SCS showed its normal morphological structure and adjacency, thus providing accurate and complete Three-dimensional imaging anatomical data of the SCS and its communicating vascular structures. This study enriches the Chinese SCS imaging anatomy data and may be valuable in clinical practice.

Recent studies have evidenced that the anatomical structure now known as the myodural bridge (MDB) connects the suboccipital musculature to the cervical spinal dura mater (SDM). In humans, the MDB passes through both the posterior atlanto-occipital and the posterior atlanto-axial interspaces. The existence of the MDB in various mammals, including flying birds (Rock pigeons and Gallus domesticus) has been previously validated. Gentoo penguins are marine birds, able to make 450 dives per day, reaching depths of up to 660 feet. While foraging, this penguin is able to reach speeds of up to 22 miles per hour. Gentoo penguins are also the world's fastest diving birds. The present study was therefore carried out to investigate the existence and characteristics of the MDB in Gentoo penguin (Pygoscelis papua), a non-flying, marine bird that can dive. For this study, six Gentoo penguin specimens were dissected to observe the existence and composition of their MDB. Histological staining was also performed to analyze the anatomic relationships and characteristic of the MDB in the Gentoo penguin. In this study, it was found that the suboccipital musculature in the Gentoo penguin consists of the rectus capitis dorsalis minor (RCDmi) muscle and rectus capitis dorsalis major (RCDma) muscle. Dense connective tissue fibers were observed connecting these two suboccipital muscles to the spinal dura mater (SDM). This dense connective tissue bridge consists of primarily type I collagen fibers. Thus, this penguin's MDB appears to be analogous to the MDB previously observed in humans. The present study evidences that the MDB not only exists in penguins but it also has unique features that distinguishes it from that of flying birds. Thus, this study advances the understanding of the morphological characteristics of the MDB in flightless, marine birds.

A dense bridge-like tissue named the myodural bridge (MDB) connecting the suboccipital muscles to the spinal dura mater was originally discovered in humans. However, recent animal studies have revealed that the MDB appears to be an evolutionarily conserved anatomic structure which may have significant physiological functions. Our previous investigations have confirmed the existence of the MDB in finless porpoises. The present authors conducted research to expound on the specificity of the MDB in the porpoise Neophocana asiaeorientalis (N.asiaeorientalis). Five carcasses of N.asiaeorientalis, with formalin fixation, were used for the present study. Two of the carcasses were used for head and neck CT scanning, three-dimensional reconstructions, and gross dissection of the suboccipital region. Another carcass was used for a P45 plastination study. Also, a carcass was used for a histological analysis of the suboccipital region and also one was used for a Scanning Electron Microscopy study. The results revealed that the MDB of the N.asiaeorientalis is actually an independent muscle originating from the caudal border of the occiput, passing through the posterior atlanto-occipital interspace, and then attaches to the cervical spinal dura mater. Thus the so called MDB of the N.asiaeorientalis is actually an independent and uniquely specialized muscle. Based on the origin and insertion of this muscle, the present authors name it the 'Occipital-Dural Muscle'. It appears that the direct pull of this muscle on the cervical spinal dura mater may affect the circulation of the cerebrospinal fluid by altering the volume of the subarachnoid space via a pumping action.

Abstract The myodural bridge (MDB) connects the suboccipital musculature to the spinal dura mater (SDM) as it passed through the posterior atlanto-occipital and the atlanto-axial interspaces. Although the actual function of the MDB is not understood at this time, it has recently been proposed that head movement may assist in powering the movement of cerebrospinal fluid (CSF) via muscular tension transmitted to the SDM via the MDB. But there is little information about it. The present study utilized dogs as the experimental model to explore the MDB’s effects on the CSF pressure (CSFP) during stimulated contractions of the suboccipital muscles as well as during manipulated movements of the atlanto-occiptal and atlanto-axial joints. The morphology of MDB was investigated by gross anatomic dissection and by histological observation utilizing both light microscopy and scanning electron microscopy. Additionally biomechanical tensile strength tests were conducted. Functionally, the CSFP was analyzed during passive head movements and electrical stimulation of the suboccipital muscles, respectively. The MDB was observed passing through both the dorsal atlanto-occipital and the atlanto-axial interspaces of the canine and consisted of collagenous fibers. The tensile strength of the collagenous fibers passing through the dorsal atlanto-occipital and atlanto-axial interspaces were 0.16 ± 0.04 MPa and 0.82 ± 0.57 MPa, respectively. Passive head movement, including lateral flexion, rotation, as well as flexion–extension, all significantly increased CSFP. Furthermore, the CSFP was significantly raised from 12.41 ± 4.58 to 13.45 ± 5.16 mmHg when the obliques capitis inferior (OCI) muscles of the examined specimens were electrically stimulated. This stimulatory effect was completely eliminated by severing the myodural bridge attachments to the OCI muscle. Head movements appeared to be an important factor affecting CSF pressure, with the MDB of the suboccipital muscles playing a key role this process. The present study provides direct evidence to support the hypothesis that the MDB may be a previously unappreciated significant power source (pump) for CSF circulation.