Subarachnoid and Subdural Hemorrhages

Some strokes are from a bad lifestyle, and others are due to trauma. Keep reading to learn more about subdural and subarachnoid hemorrhages.
Subarachnoid and Subdural Hemorrhages
Nelton Abdon Ramos Rojas

Written and verified by the doctor Nelton Abdon Ramos Rojas.

Last update: 27 May, 2022

The dura and arachnoid are two of the three meninges that humans have. Meninges are the structures that line the central nervous systemSubarachnoid and subdural hemorrhages refer to hemorrhages that happen in each of these two parts.

The meninges

The skull and spine protect the brain and spinal cord. However, they also have another protection system: the meninges. In fact, these also help with nerve development.

As the NIH Cancer Dictionary explains: “Meninges are the three layers of tissue that cover and protect the brain and spinal cord.” We have three of these layers, which are:

  • Dura mater
  • Arachnoid
  • Pia mater

The outermost and thickest, the dura mater, is separated from the bone by the epidural space. In the skull, this space doesn’t exist because the dura is attached to the bone. However, it does exist in the spinal cord where the veins and fat are.

Below the dura is the arachnoid, separated by the subdural space. This space also only becomes real when it starts bleeding, and the blood separates the two meninges.

The arachnoid extends through this space to the pia mater. The subarachnoid space has cerebrospinal fluidIn fact, it cushions pressure changes from sudden blows or movements.

Finally, the pia mater sticks to the nervous tissue, even in its grooves. In addition, scientists are still figuring out if it goes inside the tissue as well.

The inside of a brain.

Subarachnoid and subdural hemorrhages

In subarachnoid and subdural hemorrhages, the first thing is blood flowing out of the blood vessels. These vessels are in the space between the meninges. Therefore, this damages brain tissue.

However, depending on the type of hemorrhage, they will have different effects and need different treatments.

Subdural hemorrhages

Subdural hemorrhages are where blood collects in the space between the dura and arachnoid. This blood usually comes from veins after trauma. However, there are three types of hematoma depending on the time it takes to show:

  • Acute subdural hematoma
  • Subacute subdural hematoma
  • Chronic subdural hematoma

Acute subdural hematoma

This type shows up the soonest. It’s usually due to severe trauma that tears the veins that go from the cerebral cortex to the meninges.

Whoever has this usually falls immediately into a comaIn addition, some parts of the brain stop working. Some examples of this are:

  • Hemiparesis: Partial difficulty moving. In fact, this is because the injury happened to the part of the brain that handles motor skills.
  • Mydriasis: Pupils get bigger. This is because the injury happened to the area that controls the iris muscle.

Subacute subdural hematoma

This shows up slower, and is usually less serious. This is because there’s less blood. In addition, the blood also starts to clot. However, it’s also caused by trauma.

Generally, the person loses consciousness and then recovers. Then, for several days, the person will feel clouded and have issues focusing.

Chronic subdural hematoma

This is a consequence of multiple injuries over time. These have small extravasations of blood from vessels. Then, when they aren’t reabsorbed, they end up with a hematoma. In fact, this is common among the elderly.

The first symptom is usually a headache, then changes in behavior and mood. This happens little by little. In addition, people with this start to sleep more, have trouble thinking, and other symptoms.

Subarachnoid Hemorrhages

Subarachnoid hemorrhages are where blood pools between the arachnoid and the pia mater. The blood usually comes from arteries, and can have lots of different causes. The most common is the rupture of an aneurysm. However, they can have other causes too.

Aneurysms can come with headaches or even epileptic seizures before they burst. In up to one third of cases, the trigger can be something physical with an emotional component. In addition, it can happen from being in the sun for too long.

A lady with a headache.

Once they break, that’s when the hemorrhage begins. Usually, these happen between the ages of 40 and 60, and are linked with the following symptoms.

  • Vomiting
  • Clouded thoughts
  • Intense headaches
  • Pain or discomfort from light

About 48 hours later, the meningeal syndrome appears, since the meninges are irritated, and then the neck stiffens too. In addition, you may experience eye issues, like paralysis of eye movements.
Subarachnoid hemorrhages cause sequelae in up to 60% of cases. In addition, 40% of survivors will permanently rely on others in some way.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.