The relationship between myodural bridge, atrophy and hyperplasia of the suboccipital musculature, and cerebrospinal fluid dynamics.

The Myodural Bridge (MDB) is a physiological structure that is highly conserved in mammals and many of other tetrapods. It connects the suboccipital muscles to the cervical spinal dura mater (SDM) and transmits the tensile forces generated by the suboccipital muscles to the SDM. Consequently, the MDB has broader physiological potentials than just fixing the SDM. It has been proposed that MDB significantly contributes to the dynamics of cerebrospinal fluid (CSF) movements. Animal models of suboccipital muscle atrophy and hyperplasia were established utilizing local injection of BTX-A and ACE-031. In contrast, animal models with surgical severance of suboccipital muscles, and without any surgical operation were set as two types of negative control groups. CSF secretion and reabsorption rates were then measured for subsequent analysis. Our findings demonstrated a significant increase in CSF secretion rate in rats with the hyperplasia model, while there was a significant decrease in rats with the atrophy and severance groups. We observed an increase in CSF reabsorption rate in both the atrophy and hyperplasia groups, but no significant change was observed in the severance group. Additionally, our immunohistochemistry results revealed no significant change in the protein level of six selected choroid plexus-CSF-related proteins among all these groups. Therefore, it was indicated that alteration of MDB-transmitted tensile force resulted in changes of CSF secretion and reabsorption rates, suggesting the potential role that MDB may play during CSF circulation. This provides a unique research insight into CSF dynamics.

Internal Structural Connections in the Popliteus Tendon Complex with Posterior Cruciate Ligament and Clinical Implications / Conexiones Estructurales Internas en el Complejo Tendón Poplíteo con Ligamento Cruzado Posterior e Implicaciones Clínicas

SUMMARY: At present, the anatomical relationship the mid-portion of popliteus tendon complex (PTC) and the surrounding tissues is still unclear, especially its relationship to the posterior cruciate ligament (PCL). It affected the anatomical reconstruction of the posterolateral complex (PLC) injury. A total of 30 cases of the adult human knee joint fixed with formalin were used. Sagittal sections were made in 14 knee joints by the P45 plastination technique and dissection of 16 cases of knee joints. The P45 section revealed that the popliteus muscle fascia ran superiorly over the posterior edge of the tibial intercondylar eminence, and turned forward to be integrated into the PCL. Laterally, near the posterior edge of the lateral tibial plateau, the popliteus tendon penetrates through the articular capsule (AC), where two dense fibrous bundles were given off upwards by the popliteus tendon: one was the ventral fiber bundle, which ran superiorly over the posterior edge of the tibial plateau and then moved forwards to connect with the lateral meniscus; the dorsal fibers bundle ascended directly and participated in the AC. Meanwhile, the popliteus muscle dissection showed that at the posterior edge of the platform of the lateral condyle of the tibia, at the tendon-muscle transition, the PTC and AC were anchored to PCL.

En la actualidad, la relación anatómica entre la porción media del complejo tendinoso poplíteo (CTP) y los tejidos circundantes aún no está clara, especialmente su relación con el ligamento cruzado posterior (LCP). Esto afecta la reconstrucción anatómica de la lesión del complejo posterolateral (LCP). Se utilizaron un total de 30 casos de articulaciones de rodillas humanas de individuos adultos fijadas con formalina. Se realizaron cortes sagitales en 14 articulaciones de rodilla mediante la técnica de plastinación P45 y disección de 16 casos de articulaciones de rodilla. La sección P45 reveló que la fascia del músculo poplíteo discurría superiormente sobre el margen posterior de la eminencia intercondílea tibial y giraba hacia delante para integrarse en el LCP. Lateralmente, cerca del margen posterior de la platillo tibial lateral, el tendón poplíteo penetra a través de la cápsula articular (CA), donde el tendón poplíteo desprendió hacia arriba dos haces fibrosos densos: uno era el haz de fibras ventral, que corría superiormente sobre el margen posterior de la meseta tibial y luego se movió hacia adelante para conectar con el menisco lateral; el haz de fibras dorsales ascendía directamente y participaba en la CA. Por su parte, la disección del músculo poplíteo mostró que en el margen posterior del platillo del cóndilo lateral de la tibia, en la transición tendón-músculo, el CTP y el AC estaban anclados al LCP.

Detailed anatomy of the corpora-glans ligament via the P45 plastination method / Anatomía detallada de los ligamentos cuerpo cavernoso-glande mediante el método de plastinación P45

SUMMARY: The corporo-glans ligament is the ligament connecting the corpus cavernosum and the glans of the penis. The anatomical description of the corporo-glans ligaments shape is still uncertain, this knowledge affects penile reconstructive procedures. The anatomy of the corporo-glans ligament was analyzed and recorded via observing sagittal sections of 10 different penile P45 plastination sections. According to the P45 plastination sections, the corporo-glans junction displayed a fibrous tissue band connecting the distal ends of the two corpus cavernous (CC) with the glans penis (GP). The fibrous band was a round-obtuse shape and ran deep into the glans of the penis and occupied about 2/3 of the whole GP. The original end was laid in a socket embedded in the GP. The density of the fibers of the ligament at the original end close to the tunica albuginea was less than that of the other parts. The fibers originating from the tunica albuginea, directly extended to the blind end of the two CC, covering the distal end of the two CC.

El ligamento cuerpo cavernoso-glande es el ligamento que conecta el cuerpo cavernoso y el glande del pene. La descripción anatómica de la forma de los ligamentos cuerpo cavernoso -glande aún es incierta; este conocimiento afecta los procedimientos reconstructivos del pene. La anatomía del ligamento cuerpo cavernoso-glande se analizó y registró mediante la observación de 10 secciones sagitales diferentes del pene a través de plastinación P45. Según las secciones de plastinación, la unión cuerpo-glande mostraba una banda de tejido fibroso que conectaba los extremos distales de los dos cuerpos cavernosos con el glande del pene. La banda fibrosa tenía una forma redonda y obtusa y se adentraba profundamente en el glande del pene ocupando alrededor de 2/3 de él. En su origen se coloca en un espacio profundo en el glande del pene. La densidad de las fibras del ligamento cuerpo cavernoso-glande en su origen cercano a la túnica albugínea era menor que el de las otras partes. Las fibras que se originan en la túnica albugínea, se extienden directamente hasta el extremo ciego de los dos cuerpos cavernosos, cubriendo el extremo distal de estos.

The relationship between myodural bridges, hyperplasia of the suboccipital musculature, and intracranial pressure.

During mammalian evolution, the Myodural Bridges (MDB) have been shown to be highly conserved anatomical structures. However, the putative physiological function of these structures remains unclear. The MDB functionally connects the suboccipital musculature to the cervical spinal dura mater, while passing through the posterior atlanto-occipital and atlanto-axial interspaces. MDB transmits the tensile forces generated by the suboccipital muscles to the cervical dura mater. Moreover, head movements have been shown to be an important contributor to human CSF circulation. In the present study, a 16-week administration of a Myostatin-specific inhibitor, ACE-031, was injected into the suboccipital musculature of rats to establish an experimental animal model of hyperplasia of the suboccipital musculature. Using an optic fiber pressure measurement instrument, the present authors observed a significant increase in intracranial pressure (ICP) while utilizing the hyperplasia model. In contrast, surgically severing the MDB connections resulted in a significant decrease in intracranial pressure. Thus, these results indicated that muscular activation of the MDB may affect CSF circulation, suggesting a potential functional role of the MDB, and providing a new research perspective on CSF dynamics.

Identification of the myodural bridge in a venomous snake, the gloydius shedaoensis: what is the functional significance? / Identificación del puente miodural en una serpiente venenosa, gloydius shedaoensis: ¿cuál es el significado funcional?

SUMMARY: Myodural bridges (MDB) are anatomical connections between the suboccipital muscles and the cervical dura mater which pass through both the atlanto-occipital and the atlanto-axial interspaces in mammals. In our previous studies, we found that the MDB exists in seven terrestrial mammal species, two marine mammal species, two reptilian species, and one bird species. A recent study suggested that given the "ubiquity" of myodural bridges in terrestrial vertebrates, the MDB may also exist in snakes. Specifically, we focused on the Gloydius shedaoensis, a species of Agkistrodon (pit viper snake) that is only found on Shedao Island, which is in the southeastern sea of Dalian City in China. Six head and neck cadaveric specimens of Gloydius shedaoensis were examined. Three specimens were used for anatomical dissection and the remaining three cadaveric specimens were utilized for histological analysis. The present study confirmed the existence of the MDB in the Gloydius shedaoensis. The snake's spinalis muscles originated from the posterior edge of the supraoccipital bones and the dorsal facet of the exocciput, and then extended on both sides of the spinous processes of the spine, merging with the semispinalis muscles. On the ventral aspect of this muscular complex, it gave off fibers of the MDB. These MDB fibers twisted around the posterior margin of the exocciput and then passed through the atlanto-occipital interspace, finally terminating on the dura mater. We observed that the MDB also existed in all of the snakes' intervertebral joints. These same histological findings were also observed in the Gloydius brevicaudus, which was used as a control specimen for the Gloydius shedaoensis. In snakes the spinal canal is longer than that observed in most other animals. Considering the unique locomotive style of snakes, our findings contribute to support the hypothesis that the MDB could modulate cerebrospinal fluid (CSF) pulsations.

RESUMEN: Los puentes miodurales (MDB) son conexiones anatómicas entre los músculos suboccipitales y la duramadre cervical que pasan a través de los espacios intermedios atlanto-occipital y atlanto-axial en los mamíferos. En nuestros estudios anteriores, encontramos que el MDB existe en siete especies de mamíferos terrestres, dos especies de mamíferos marinos, dos especies de reptiles y una especie de ave. Un estudio reciente sugirió que dada la "ubicuidad" de los puentes miodurales en los vertebrados terrestres, el MDB también puede existir en las serpientes. Específicamente, nos enfocamos en Gloydius shedaoensis, una especie de Agkistrodon (serpiente víbora) que solo se encuentra en la isla Shedao, en el mar sureste de la ciudad de Dalian en China. Se examinaron seis especímenes cadavéricos de cabeza y cuello de Gloydius shedaoensis. Se utilizaron tres especímenes para la disección anatómica y los tres especímenes cadavéricos restantes se utilizaron para el análisis histológico. El presente estudio confirmó la existencia del MDB en Gloydius shedaoensis. Los músculos espinosos de la serpiente se originaron en el margen posterior de los huesos supraoccipital y la cara dorsal del exoccipucio, y luego se extendieron a ambos lados de los procesos espinosas de la columna vertebral, fusionándose con los músculos semiespinosos. En la cara ventral de este complejo muscular se desprendían fibras del MDB. Estas fibras MDB se ubican alrededor del margen posterior del exoccipucio y luego atraviesan el interespacio atlanto-occipital, terminando finalmente en la duramadre. Observamos que el MDB también existía en todas las articulaciones intervertebrales de las serpientes. Estos mismos hallazgos histológicos también se observaron en Gloydius brevicaudus, que se utilizó como muestra de control para Gloydius shedaoensis. En las serpientes, el canal espinal es más largo que el observado en la mayoría de los otros animales. Teniendo en cuenta el estilo único locomotor de las serpientes, nuestros hallazgos contribuyen a respaldar la hipótesis de que el MDB podría modular las pulsaciones del líquido cerebroespinal.

The myodural bridges' existence in the sperm whale.

Recent studies have identified that the myodural bridge (MDB) is located between the suboccipital muscles and cervical dura mater in the posterior atlanto-occipital interspace within humans. The myodural bridge has been considered to have a significant role in physiological functions. However, there is little information about the myodural bridge in marine mammals; we conducted this study to investigate and examine the morphology of the myodural bridge in a sperm whale. We also aim to discuss the physiological functions of the myodural bridge. In this study, a 15.1-meter long sperm whale carcass was examined. Multiple methods were conducted to examine the bridges of the sperm whale which included dissection, P45 plastination and histological analysis. This study confirmed the existence of the myodural bridge in the sperm whale and shows there are two types of the bridge in the sperm whale: one type was the occipital-dural bridge (ODB), the other type was the MDB. A large venous plexus was found within the epidural space and this venous plexus is thought to contain a great amount of blood when in deep water and thus the movements of suboccipital muscles could be a unique power source that drives cerebrospinal fluid circulation.