Dura mater

The dura mater has several functions and layers. The dura mater is a membrane that envelops the arachnoid mater. It surrounds and supports the dural sinuses (also called dural venous sinuses, cerebral sinuses, or cranial sinuses) and carries blood from the brain toward the heart.

Cranial dura mater has two layers called lamellae, a superficial layer (also called the periosteal layer), which serves as the skull's inner periosteum, called the endocranium and a deep layer called the meningeal layer. When it covers the spinal cord it is known as the dural sac or thecal sac. Unlike cranial dura mater, spinal dura mater only has one layer, known as the meningeal layer. The potential space between these two layers is known as the epidural space. [2]

Folds and reflections

Spinal reflections and folds.

The dura separates into two layers at dural reflections (also known as dural folds), places where the inner dural layer is reflected as sheet-like protrusions into the cranial cavity. There are two main dural reflections:

• The tentorium cerebelli exists between and separates the cerebellum and brainstem from the occipital lobes of the cerebrum.[3]
• The falx cerebri, which separates the two hemispheres of the brain, is located in the longitudinal cerebral fissure between the hemispheres.[4]

Two other dural infoldings are the cerebellar falx and the sellar diaphragm:

• The cerebellar falx (falx cerebelli) is a vertical dural infolding that lies inferior to the cerebellar tentorium in the posterior part of the posterior cranial fossa. It partially separates the cerebellar hemispheres.
• The sellar diaphragm is the smallest dural infolding and is a circular sheet of dura that is suspended between the clinoid processes, forming a partial roof over the hypophysial fossa. The sellar diaphgram covers the pituitary gland in this fossa and has an aperture for passage of the infundibulum (pituitary stalk) and hypophysial veins.

Many medical conditions involve the dura mater. A subdural hematoma occurs when there is an abnormal collection of blood between the dura and the arachnoid, usually as a result of torn bridging veins secondary to head trauma. An epidural hematoma is a collection of blood between the dura and the inner surface of the skull, and is usually due to arterial bleeding. Intradural procedures, such as removal of a brain tumour, or treatment of trigeminal neuralgia via a microvascular decompression require that an incision is made to the dura mater. To achieve a watertight repair and avoid potential post-operative complications the dura is typically closed with sutures. In the event that there is a dural deficiency, a dural substitute may be used to replace this membrane. Small gaps in the dura can be covered with a surgical sealant film.

In 2011, researchers discovered a connective tissue bridge from the rectus capitis posterior major to the cervical dura mater. Various clinical manifestations may be linked to this anatomical relationship such as headaches, trigeminal neuralgia and other symptoms that involved the cervical dura.[7] The rectus capitis posterior minor has a similar attachment.[8]

The dura-muscular, dura-ligamentous connections in the upper cervical spine and occipital areas may provide anatomic and physiologic answers to the cause of the cervicogenic headache. This proposal would further explain manipulation's efficacy in the treatment of cervicogenic headache.[9]

The American Red Cross and some other agencies accepting blood donations consider dura mater transplants, along with receipt of pituitary-derived growth hormone, a risk factor due to concerns about Creutzfeldt–Jakob disease.[10]

Cerebellar tonsillar ectopia, or Chiari, is a condition that was previously thought to be congenital but can be induced by trauma, particularly whiplash trauma.[11] Dural strain may be pulling the cerebellum inferiorly, or skull distortions may be pushing the brain inferiorly.

Dural ectasia is the enlargement of the dura and is common in connective tissue disorders, such as Marfan syndrome and Ehlers–Danlos syndrome. These conditions are sometimes found in conjunction with Arnold–Chiari malformation.

Spontaneous cerebrospinal fluid leak is the fluid and pressure loss of spinal fluid due to holes in the dura mater.

The name dura mater derives from the Latin for tough mother (or hard mother),[12] a loan translation of Arabic أم الدماغ الصفيقة (umm al-dimāgh al-ṣafīqah), literally 'thick mother of the brain', matrix of the brain,[13][14] and is also referred to by the term "pachymeninx" (plural "pachymeninges").[13]

• 
  Dura mater (spinal section)
• 
  Diagrammatic representation of a section across the top of the skull, showing the membranes of the brain, etc.
• 
  Diagrammatic transverse section of the medulla spinalis and its membranes.
• 
  Spinal cord. Spinal membranes and nerve roots.Deep dissection. Posterior view.
• 
  Spinal cord. Spinal membranes and nerve roots.Deep dissection. Posterior view
• 
  Autopsy. Dura mater is retracted by the forceps.

• Meninges
• Pia mater
• Arachnoid mater

• Media related to Dura mater at Wikimedia Commons
• youtube: exposure of falx cerebri, dura mater & arachnoid