what is the most common cause of a subarachnoid hemorrhage
Head injury or a ruptured brain aneurysm is the most common cause of a subarachnoid hemorrhage

Head injury is the most common cause of a subarachnoid hemorrhage. In people without head trauma, however, a subarachnoid hemorrhage is usually caused by ruptured brain aneurysm. A brain aneurysm occurs when there is abnormal bulging or ballooning of a blood vessel that can burst and bleed into the brain.

Another potential cause of a subarachnoid hemorrhage is cerebral arteriovenous malformation (AVM), which refers to abnormal tangles of the blood vessels that connect the arteries and veins in the brain. AVMs generally develop before birth.

What is a subarachnoid hemorrhage?

A subarachnoid hemorrhage is a medical emergency that occurs when there is bleeding from a damaged artery in the subarachnoid space present around the brain. 

The brain is located inside a bony covering called the cranium. Both the brain and spinal cord are surrounded by three protective layers of tissue called the meninges. These meninges are called the pia mater, arachnoid, and dura mater.

The space between the pia mater (the layer closest to the brain) and arachnoid is called the subarachnoid space. This space contains cerebrospinal fluid (CSF). Because the cranium is a rigid or non-expandable structure, bleeding in the subarachnoid space exerts pressure on the brain, which can lead to a severe disability or even death.

What are risk factors for a subarachnoid hemorrhage?

Sometimes, a subarachnoid hemorrhage may occur without an obvious cause (idiopathic). Risk factors that may put you at risk of subarachnoid hemorrhage include: 

What are the symptoms of a subarachnoid hemorrhage?

The most remarkable symptom of a subarachnoid hemorrhage is a sudden and severe headache, often called a thunderclap headache. People often report it as the worst headache of their life. The headache is severe in intensity and builds rapidly within minutes. 

Other symptoms may vary depending on the site of the hemorrhage in the brain:

How is a subarachnoid hemorrhage treated?

A subarachnoid hemorrhage requires urgent diagnosis and treatment. The affected person must be rushed to the emergency room, although management starts with prehospital care. 

Treatment is aimed at:

  • Stopping bleeding and preventing further bleeding
  • Treating the cause of bleeding
  • Relieving symptoms
  • Preventing disability and life-threatening complications

Doctors may perform surgery to relieve excess pressure from the brain caused by the accumulated blood and prevent further bleeding. Bleeding may be stopped by clipping the ruptured aneurysm. Alternatively, other procedures such as endovascular embolization or stenting may be required. 

In some cases, doctors may also treat underlying risk factors such as high blood pressure. Additional supportive care may include efforts to maintain breathing, blood pressure, and electrolytes as well as to relieve pain and anxiety and prevent/treat seizures.

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Medically Reviewed on 8/27/2021
References
https://emedicine.medscape.com/article/1164341-overview

https://www.uclahealth.org/neurosurgery/subarachnoid-hemorrhage

https://emedicine.medscape.com/article/794076-overview