What is the Dura Mater?
The dura mater, or pachymeninx, is the outermost, toughest, and most fibrous of the three membranes, or meninges, covering the brain and spinal cord. The pia mater and arachnoid mater make up the remaining layers of the meninges, with the pia mater being the innermost layer. It is made up of two layers itself; a superficial layer and the deeper dura mater proper.
The meninges fill with cerebrospinal fluid between the pia mater and arachnoid. The primary function of the cerebrospinal fluid and meninges is to cover and protect the central nervous system. Being the toughest, outermost layer, the dura mater, often called just the dura, is thicker than the other two layers and helps to restrict movement of the brain within the skull. Parts of the this tough layer also divide the brain into its two hemispheres.
The dura mater also has several vein-like sinuses that help carry oxygen-rich blood back to the heart after it has traveled to the brain. While these veins have no valves, they allow for drainage of normal blood flow. Excessive bleeding that causes an abnormal amount of blood to collect between the dura and the arachnoid is known as a subdural hematoma. This condition is usually the result of head injury from trauma. Similarly, a collection of blood between the dura and the inner skull is called an epidermal hematoma and is typically the result of arterial bleeding.
The dura mater has been used for grafting, primarily during neurosurgery, but also in other procedures. A disease known as Creutzfeldt-Jakob Disease (CJD), which is a rare, degenerative brain disease, is also known to be transmittable during such a graft.
Meningitis is an infection of the meninges, which is most commonly caused by virus but can also be caused by bacteria. Bacterial meningitis is less common, but is far more serious than viral meningitis, which often resolves on its own with no treatment. Fever, stiff neck, and severe headache are common symptoms of meningitis, the latter two being caused by the effect the infection has on the dura mater and other membranes.
I recently had a colleague, in his 50s, get meningitis, I believe bacterial. They actually had to induce a coma for a week or so. He is fine now, and recovering slowly, but it really is a scary disease.
So this explains to me why some people who get meningitis die quickly, while others have long term damage and still others get better easily. Not only because there are two different forms, but because I imagine different people's dura mater and other meninges must react differently to the attack of the virus or bacteria.
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