The myodural bridges' existence in the sperm whale.

Pei Liu,Nan Zheng,Hongjin Sui,Shengbo Yu,Campbell Gilmore,Yanyan Chi,Yutong Zhou,Xiaoying Yuan,Pu Chun,Chan Li,Songhai Li

doi:10.1371/journal.pone.0200260

Abstract

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.

Highlights

The suboccipital region is one of the most complicated areas of the human body
The atlanto-occipital interspace was enclosed by the dorsal atlanto-occipital membrane (DAOM), which originates from the upper boundary and terminated at the lower boundary of the atlanto-occipital interspace
In humans the myodural bridge (MDB) has been confirmed to exist between the deep suboccipital muscles, which includes the rectus capitis posterior minor (RCPmi) [1, 2, 10, 28, 29], rectus capitis posterior major (RCPma) [13, 14, 29], obliquus capitis inferior (OCI) [12, 15, 29] and the cervical dura mater

Summary

Introduction

The suboccipital region is one of the most complicated areas of the human body. As the connection of the head and neck, it plays important roles in head movement and in nervous impulse transmission of the brain and spinal cord. A bridge connecting the suboccipital musculature and cervical dura mater was found in the atlanto-occipital interspace by Kahn [1], and termed the “myodural bridge (MDB)” by Hack [2]. The MDB was first described as an anatomical bridge, which bridges the epidural space between the rectus capitis posterior minor (RCPmi) and the cervical dura mater. A few years later, the existence of the MDB had been observed between the cervical dura matter and multiple suboccipital muscles including the RCPmi, the rectus capitis posterior major (RCPma) and the obliquus capitis inferior (OCI) [3]. The existence of bridges between the nuchal ligament (NL) and the dura mater is controversial as researchers debate its source [4,5,6,7,8]

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