Pathology

How Berry Aneurysm causes Subarachnoid Hemorrhage



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What is a berry aneurysm?

The brain is a complex collection of tissues which include brain matter, covering membranes as well as the blood vessels. The vascular structure within the brain consist of two major circulations known as the anterior and posterior circulation and these two circulations link together through the ‘circle of willis’ from which smaller blood vessels runs in to the brain matter. In such instances, the points in which main blood vessels are traversed by smaller vessels can become intrinsically weak. At the same time, genetic constituents would also play a role in making these areas possess a weaker blood vessel wall.

When the blood vessels contain weaker walls, it is possible for such blood vessels to give in at times of persistent high blood pressures to form an out pouching from these sites. These out pouching will appear as a ‘berry’ and would contain a sac and a stem. Such an out pouching would be known as a berry aneurysm and are very susceptible towards a rupture.

Apart from the genetic susceptibility, certain other causes can also be associated with weakened blood vessel wall and among them head trauma, infections, connective tissue disorders as well as medical problems which leads to high blood pressure are considered rather common.

What is the subarachnoid space?

Subarachnoid space is considered to be the gap between the pia mater and the arachnoid membrane and is usually filled by the cerebrospinal fluid. Although the pia mater closely follows the contours of the brain and is vehemently attaches to the surface of the brain matter, the arachnoid membrane neither attaches to the pia mater nor does it attach itself to the dura mater which forms a covering around the arachnoid.  

How does the bleeding occur?

As mentioned before, some of the berry aneurysms that are present in the vessel walls can arise in the subarachnoid space and due to pressure changes in the vessel lumen they can get ruptured. The rupture can result in a bleeding which can range from a mild bleed to a massive hemorrhage. In such instances, the patients usually complains of a sudden severe headache which is often described as a ‘thunder clap’ headache and would also be associated with several other symptoms including loss of consciousness.

Things to remember

Usually, even if the person develops berry aneurisms it would not give rise to any symptoms unless it gets ruptured. Thus, as it happens unknowingly, it would be prudent to avoid smoking, cocaine abuse as well as obtain medications to control the blood pressure to maintain it at a normal level or else to prevent the shooting up of pressure from time to time.

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