The myodural bridge or miodural ligament is a bridge of

connective tissue Connective tissue is one of the four primary types of animal tissue, a group of cells that are similar in structure, along with epithelial tissue, muscle tissue, and nervous tissue. It develops mostly from the mesenchyme, derived from the mesod ...

that extends between the

suboccipital muscles The suboccipital muscles are a group of muscles defined by their location to the occiput. Suboccipital muscles are located below the occipital bone The occipital bone () is a neurocranium, cranial dermal bone and the main bone of the occiput ( ...

and the cervical spinal dura mater, the outer membrane that envelops the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

. It provides a physical connection between the

musculoskeletal The human musculoskeletal system (also known as the human locomotor system, and previously the activity system) is an organ system that gives humans the ability to move using their muscular and skeletal systems. The musculoskeletal system provid ...

and

nervous system In biology, the nervous system is the complex system, highly complex part of an animal that coordinates its behavior, actions and sense, sensory information by transmitting action potential, signals to and from different parts of its body. Th ...

s, and the circulation of

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless Extracellular fluid#Transcellular fluid, transcellular body fluid found within the meninges, meningeal tissue that surrounds the vertebrate brain and spinal cord, and in the ventricular system, ven ...

. Its importance has been highlighted by various authors. The myodural bridge is mainly formed by

muscular MUSCULAR (DS-200B), located in the United Kingdom, is the name of a surveillance program jointly operated by Britain's Government Communications Headquarters (GCHQ) and the U.S. National Security Agency (NSA) that was revealed by documents release ...

and tendinous components. This bridge originates in the deep layers of the

, specifically in the

rectus capitis posterior minor muscle The rectus capitis posterior minor (or rectus capitis posticus minor) is a muscle in the upper back part of the neck. It is one of the suboccipital muscles. Its inferior attachment is at the posterior arch of atlas; its superior attachment is on ...

, and extends to join the dura mater of the cervical

. This structural connection forms a continuous link from the base of the

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

to the top of the

cervical spine In tetrapods, cervical vertebrae (: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In sauro ...

. Recent studies postulate the existence and functional importance of the myodural bridge in mammals. This membranous anatomical structure was discovered in the mid-90s. According to forensic studies conducted, this ligament has various patterns of insertion although the general consensus is that it primarily adheres to the

occipital bone The occipital bone () is a neurocranium, cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone lies over the occipital lob ...

, to the

, to the posterior arch of the

atlas An atlas is a collection of maps; it is typically a bundle of world map, maps of Earth or of a continent or region of Earth. Advances in astronomy have also resulted in atlases of the celestial sphere or of other planets. Atlases have traditio ...

bone, and to the dura mater. The term "Miodural Bridge Complex" postulates it as a new functional structure. It is a relevant anatomical structure due to its role in the

biomechanics Biomechanics is the study of the structure, function and motion of the mechanical aspects of biological systems, at any level from whole organisms to Organ (anatomy), organs, Cell (biology), cells and cell organelles, using the methods of mechani ...

and physiology of the

human body The human body is the entire structure of a Human, human being. It is composed of many different types of Cell (biology), cells that together create Tissue (biology), tissues and subsequently Organ (biology), organs and then Organ system, org ...

Physiological functions

Among its

physiological Physiology (; ) is the science, scientific study of function (biology), functions and mechanism (biology), mechanisms in a life, living system. As a branches of science, subdiscipline of biology, physiology focuses on how organisms, organ syst ...

functions are the biomechanical stabilization of the atlantooccipital joint and the dura mater, the regulation of

, mediation in

nociceptive In physiology, nociception , also nocioception; ) is the sensory nervous system's process of encoding noxious stimuli. It deals with a series of events and processes required for an organism to receive a painful stimulus, convert it to a molecular ...

transduction, monitoring of dura mater tension, and sensorimotor regulation in the cervical region (coordination of movements and sensory perception). The myodural bridge is also involved in

proprioceptive Proprioception ( ) is the sense of self-movement, force, and body position. Proprioception is mediated by proprioceptors, a type of sensory receptor, located within muscles, tendons, and joints. Most animals possess multiple subtypes of propri ...

transmission, preventing obstructions of the subarachnoid space and the cerebromedullary cistern.

Pathophysiology and clinical relevance

The myodural bridge displays physiological reciprocities with the

, which include the inferior oblique capitis (OCI), the

rectus capitis posterior major The rectus capitis posterior major (or rectus capitis posticus major) is a muscle in the upper back part of the neck. It is one of the suboccipital muscles. Its inferior attachment is at the spinous process of the axis (Second cervical vertebra); ...

(RCPM), and the

rectus capitis posterior minor The rectus capitis posterior minor (or rectus capitis posticus minor) is a muscle in the upper back part of the neck. It is one of the suboccipital muscles. Its inferior attachment is at the posterior arch of atlas; its superior attachment is ont ...

(RCPm), in addition to the posterior atlanto-occipital membrane and several meningo-vertebral structures. This may lead the myodural bridge to exert torque, traction, or shortening on the dura mater, creating abnormal tension that can result in head protrusion,

headaches A headache, also known as cephalalgia, is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of depression in those with severe headaches. Head ...

, and

vertigo Vertigo is a condition in which a person has the sensation that they are moving, or that objects around them are moving, when they are not. Often it feels like a spinning or swaying movement. It may be associated with nausea, vomiting, perspira ...

of cervicogenic origin. Pathomechanical or physiological abnormalities of the myodural bridge can affect the

blood volume Blood volume (volemia) is the volume of blood ( blood cells and plasma) in the circulatory system of any individual. Humans A typical adult has a blood volume of approximately 5 liters, with females and males having approximately the same blood p ...

in the suboccipital cavernous sinuses, leading to

cognitive disorders Neurocognitive disorders (NCDs), also known as cognitive disorders (CDs), are a category of mental health disorders that primarily affect cognitive abilities including learning, memory, perception, and problem-solving. Neurocognitive disorders in ...

associated with

(CSF) dysfunctions. It has also been proposed as an etiological factor in the symptoms associated with Arnold-Chiari type I disease. The role of the posterior cervical musculature in sensorimotor control, cervicocephalic pain, and

stabilization goes through biomechanical and anatomical interactions with the miodural bridge. There are soft tissue anatomical connections that cross the cervical

epidural space In anatomy, the epidural space is the potential space between the dura mater and vertebrae ( spine). The anatomy term "epidural space" has its origin in the Ancient Greek language; , "on, upon" + dura mater also known as "epidural cavity", "e ...

and link the suboccipital muscle

fascia A fascia (; : fasciae or fascias; adjective fascial; ) is a generic term for macroscopic membranous bodily structures. Fasciae are classified as superficial, visceral or deep, and further designated according to their anatomical location. ...

with the dura mater. The myodural bridge provides both passive and active anchoring to the spinal cord. It is also involved in the dura mater tension monitoring system to prevent dural folds and maintain the permeability of the spinal cord. Modulation of dura mater tension can be initiated through a sensory reflex to the contractile muscle tissues. Unanticipated movements, such as hyperflexion-extension injuries, stimulate the deep

and transmit traction forces through the miodural bridge to the cervical dura mater.

References

{{reflist Connective tissue Ligaments of the head and neck