Abstract
The “myodural bridge” was described in literatures as a dense fibrous tissue connecting the sub-occipital musculature with the spinal dura mater in human studies. Now the concept of “myodural bridge” was perceived as an exact anatomical structure presumably essential for critical physiological functions in human body, and might exist in other mammals as well. To determine the existence of the “myodural bridge” in other mammals and to lay a foundation for the functional study, we examined representatives in five different mammalian orders. Based on the anatomical dissections, P45 plastinated sections and histological sections, we found that a dense fibrous tissue connected the rectus capitisdorsalis minor and the spinal dura mater through the dorsal atlanto-occipital interspace with or without the medium of the posterior atlanto-occipital membrane. These observed connective tissues were very similar to the “myodural bridge” previously described in humans. We proposed that the “myodural bridge”, as an evolutionally conserved structure, presents in many other mammals. Moreover, we believed that the “myodural bridge” might be a homologous organ in mammals. Thus, this study could provide an insight for our understanding the physiological significance of the “myodural bridge”, especially in human.
Highlights
The sub-occipital region is one of the most complex anatomical regions in the human body
In Macacamulatta, Canisfamiliaris, Feliscatus, Oryctolaguscuniculus, Rattusnorvegicus and Caviaporcellus, the post-occipital muscles were found to consist of the rectus capitis dorsal major (RCDma, same as rectus capitis posterior major (RCPma) in humans), the rectus capitis dorsal minor (RCDmi, same as rectus capitis posterior minor (RCPmi) as in humans), the oblique capitis anterior (OCA, same as OCS in humans), and the oblique capitis posterior (OCP, same as oblique capitis inferior (OCI) in humans) (Fig. 1A–F)
In 1995, Hack revealed a dense band of tissue connecting the RCPmi and posterior atlanto-occipital (PAO) membrane, and the latter was intimately attached to the outer surface of the dura mater by a fine connective tissue bridge, especially near the midline[1]
Summary
The sub-occipital region is one of the most complex anatomical regions in the human body. Dissections of 11 human cadavers by Hack et al.[1] revealed a dense band of tissue connecting the RCPmi and the posterior atlanto-occipital (PAO) membrane. It was suggested that the MDB might act to prevent in-folding of the spinal dura mater during head extension[1], or act to trigger cervical neck extensors that would resist hyperflexion or hypertranslation[12], or play a role in maintaining the integrity of the subarachnoid space[5], or work as a pump to propel the circulation of cerebral spinal fluid[13]. Those proposed functions have not been demonstrated so far. To determine the universal existence of the MDB in mammals and to lay the foundation for exploring the MDB’ functions in humans, we examined the presence of the MDB in seven different mammals with a combination of techniques including gross dissection, P45 sheet plastination and histological staining
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