What Is the Most Common Cause of 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.

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

• Uncontrolled high blood pressure
• Use of blood thinners
• Smoking
• Excess alcohol consumption
• Drug abuse (cocaine and mephentermine) 
• Connective tissue disorders

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:

• Altered or loss of consciousness
• Nausea and vomiting
• Confusion
• Slurred speech
• Neck rigidity or stiffness
• Vision problems such as diplopia (double vision)
• Photophobia (intolerance to bright light)
• Weakness in the limbs
• Difficulty walking or maintaining posture
• Seizures
• Numbness in any part of the body
• Memory impairment

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.