The myodural bridge existing in the Nephocaena phocaenoides

Abstract

Recent studies have identified that the myodural bridge (MDB) between the rectus capitis posterior minor (RCPmi) and the cervical spinal dura mater in the posterior atlanto-occipital interspace in humans. And it was supposed that the MDB may play essential physiological roles. As a result, the MDB is possibly a highly conserved structure in the evolution of mammals. However, there is little confirmative description about the existence of the MDB in marine mammals. The objective of this study was to explore the existence and the fiber property of the MDB in the Neophocaena phocaenoides. Six cadavers of the Neophocaena phocaenoides with formalin fixation were used in this study. One was used for head and neck CT scanning and three-dimensional (3D) reconstruction and suboccipital region dissection, two were for sectional observation by P45 plastinated sheets of head and neck, and three were for histological analysis of suboccipial structures. This is the first study to demonstrate the existence of the MDB in the aquatic mammals. The rectus capitis dorsal minor (RCDmi) originated from the inferior border of the occiput and inserted into the cervical spinal dura mater. At the ventral aspect of the RCDmi, the MDB directly extended through the posterior atlanto-occipital interspace and connected with the cervical spinal dura mater which was consisted of type Ⅰ collagen. In addition, the dorsal atlanto-occipital membrane was not found in the Neophocaena phocaenoides. The tendinous myodural bridge extended from the RCDmi to the spinal dura mater through the posterior atlanto-occipital interspace in the Neophocaena phocaenoides.

The myodural bridges' existence in the sperm whale

“…The MDB has been found in the suboccipital region of quadrupedal terrestrial mammals, which includes cats, rats, dogs, rabbits, guinea pigs, macaques, and mandrill [ 25 ], as well as one reptilian species (the siamensis crocodile) [ 26 ]. Regarding marine mammals, we recently confirmed the existence of the MDB in the finless porpoise ( Neophocaena phocaenoides ) [ 27 ]. In this study, we confirmed the existence of the MDB in the sperm whale via multiple research methods.…”

“…The fact that MDB exists universally in mammals has been reported only in a few studies so far. Our previous studies have proved the existence of the MDB in seven terrestrial mammal orders [ 25 ], one reptilian species (the siamensis crocodile) [ 26 ] and six finless porpoise ( Neophocaena phocaenoides ) [ 27 ]. The objective of this study is to examine the morphology of the MDB within other marine mammals and to discuss possible physiological functions from an evolutionary perspective.…”

Relationship between the sectional area of the rectus capitis posterior minor and the to be named ligament from 3D MR imaging

“…The myodural bridge (MDB) is a connective tissue band that connects the suboccipital muscles and nuchal ligament (NL) with the cervical spinal dura mater (SDM) [1][2][3][4][5][6]. It has been recently confirmed as a conserved structure in mammals [7][8][9]. The MDB has a critical role in transmitting tensile force from its muscular and ligamentous components to the SDM, which has an essential role in the etiology of headache and cervicocephalic pain syndrome [10][11][12][13][14].…”

Existence and Features of the Myodural Bridge in Gentoo Penguins: a morphological study

“…According to rencent reports, MDB dysfunction may occur with pathological conditions of the RCPmi muscle, resulting in the generation of cervicogenic headache, and other craniofacial disorders [13][14][15][16][17]. In recent years, researchers have found that the MDB is a universal structure in mammals [18], including marine mammals (Nephocaena phocaenoides and sperm whales) [19,20]. The MDB also exists in reptiles (Siamese crocodile and Trachemys scripta elegans) [21,22], as well as in birds (Rock pigeons and Gallus domesticus) [23,24].…”