The dura mater and the arachnoid are two of the three meninges that the human being has. The meninges are the structures that line the central nervous system. A subdural or subarachnoid hemorrhage refers to a hemorrhage that occurs below each of these two meninges.
The brain and spinal cord are protected by the skull and spine. But they also have another protection system: the meninges, also involved in nervous development. We have three meninges, from outside to inside they are:
- Dura mater.
- Pia mater.
The outermost and thickest, the dura, it is separated from the bone by the epidural space. In the skull, this space is virtual, that is, it does not exist because the dura is attached to the bone. However, it does exist in the spinal cord and is occupied by veins and fat.
Below the dura is the arachnoid, separated by the subdural space. This space is also virtual and only becomes real when a hemorrhage occurs and the blood separates the two meninges.
The arachnoid sends to the pia mater a series of extensions that cross the subarachnoid space. The subarachnoid space is occupied by cerebrospinal fluid which is responsible, among other things, for cushioning pressure changes due to shocks or sudden movements.
By last, the pia mater is intimately attached to the nervous tissue, accompanying it even in its furrows. The possibility of even accompanying it to the interior of the tissue is under investigation.
See also: 5 ways to keep your nervous system healthy
Subdural or subarachnoid hemorrhage
In a subdural or subarachnoid hemorrhage, the first circumstance is the leakage of blood from the blood vessels, which is stored in the spaces between the meninges. This causes damage to the brain tissue, thus generating various clinical conditions.
However, depending on whether the hemorrhage is subdural or subarachnoid, the triggers, the course of the pathology and its clinic will be different.
Subdural hemorrhage is defined as the collection of blood in the virtual space between the dura mater and the arachnoid. This blood is usually of venous origin and usually responds to traumatic causes. However, there are three types of subdural hematoma depending on the time it takes to become evident:
- Acute subdural hematoma.
- Subacute subdural hematoma.
- Chronic subdural hematoma.
Acute subdural hematoma
It is the one that is evidenced earlier. It is usually due to an intense trauma that tears the veins that go from the cerebral cortex to the meninges.
Whoever experiences it usually falls into a coma immediately. In addition, signs of hemispheric focality usually appear. This means that some specific part of the brain stops working. Some examples of focality are:
- Hemiparesis: partial impotence for movement due to injury to the area that governs motor skills.
- Mydriasis: abnormal increase in pupillary diameter due to injury to the area that controls the iris muscle.
Subdural subdural hematoma
It is somewhat slower in evolution, and is usually less severe. This is because the amount of extravasated blood is less and the coagulation mechanisms can stop the bleeding. Its cause is also usually traumatic.
First, you usually lose your conscience and then recover it. Then, for several days you will experience a progressive obnubilación, in addition to signs of focalidad.
Chronic subdural hematoma
It is the consequence of multiple minor traumas over time. These give rise to small extravasations of blood that, when not reabsorbed, end up giving rise to a subdural hematoma of considerable dimensions. It is relatively common in the elderly.
The early symptom is usually headache or headache, associated with alterations of affectivity and behavior. The deterioration is progressive, with a tendency to sleep, slow thinking and others.
Subarachnoid hemorrhage is defined as the collection of blood between the arachnoid and the pia mater. The blood is usually of arterial origin and obeys various causes. The most frequent is the rupture of an aneurysm, but it can also be due to vascular malformations.
Aneurysms may manifest with headaches or epileptic seizures before rupture. In up to a third of the cases, the triggering factor for rupture of the aneurysm is a physical effort with an emotional component or long exposure to the sun.
See also: Health tips to prevent an aneurysm
Once they are broken, subarachnoid hemorrhage begins. Most often it occurs between 40 and 60 years. The beginning of the clinic is abrupt and appear:
- Very intense headache.
- Photophobia (intolerance to light due to pain or discomfort).
Around 48 hours later the meningeal syndrome usually appears, due to irritation of the meninges. Thus, the anterior symptoms are joined neck stiffness. Focal deficits may also appear, such as paralysis of eye movements.
Subarachnoid hemorrhages cause sequelae in up to 60% of those who experience them. In addition, 40% of survivors develop some type of dependency.