About 80% of subarachnoid hemorrhages are caused by a ruptured brain aneurysm. A brain aneurysm is a bulge in a weak spot in a blood vessel wall, in the brain.
It's unknown why brain aneurysms develop, but risk factors include:
- Smoking
- High blood pressure (hypertension)
- Excessive alcohol consumption
- Severe head injury
- Family history of brain aneurysms
- Autosomal dominant polycystic kidney disease (ADPKD)
Subarachnoid hemorrhages sometimes occur during physical effort or straining, such as:
- Coughing
- Straining to have a bowel movement
- Lifting heavy objects
- Vigorous sex
What Is a Subarachnoid Hemorrhage?
A subarachnoid hemorrhage is a type of stroke usually caused by a burst blood vessel in the brain (a ruptured brain aneurysm).
What Are Symptoms of a Subarachnoid Hemorrhage?
There are usually no early signs of subarachnoid hemorrhages. When symptoms occur, they may include:
- Sudden severe headache unlike anything experienced before (“the worst headache of your life”)
- Stiff neck
- Nausea
- Vomiting
- Sensitivity to light
- Blurred or double vision
- Stroke-like symptoms
- Slurred speech
- Weakness on one side of the body
- Loss of consciousness or convulsions
A subarachnoid hemorrhage is a medical emergency. Call 911 and get to a hospital’s emergency department (do not drive yourself) immediately if you or someone you are with experiences any symptoms of subarachnoid hemorrhage.
How Is a Subarachnoid Hemorrhage Diagnosed?
A subarachnoid hemorrhage is diagnosed in the hospital with tests such as:
- Computerized tomography (CT) scan to check for signs of a brain hemorrhage
- Lumbar puncture to sample cerebrospinal fluid that surrounds the brain and spinal cord to check for signs of bleeding
If the results of the CT scan or lumbar puncture confirm a subarachnoid hemorrhage, additional testing is performed to determine treatment, including:
- Computed tomography angiography (CTA)
- Magnetic resonance angiography (MRA)
- Angiogram
What Is the Treatment for a Subarachnoid Hemorrhage?
A subarachnoid hemorrhage is a medical emergency and immediate treatment is needed to help reduce the risk of brain damage.
If a subarachnoid hemorrhage is confirmed or strongly suspected, patients are usually transferred to a specialist neuroscience unit that may include neurologists, neurosurgeons, neuroradiologists, and neurointensivists.
Treatment for a subarachnoid hemorrhage involves stopping the bleeding, which may be done by:
- Surgery to place a small clip on the blood vessel to stop blood from leaking into the brain
- An endovascular coil placed in the artery in that is bleeding
Long-term treatment for a subarachnoid hemorrhage involves addressing risk factors for the bleeding:
- Quit smoking
- Manage conditions such as high blood pressure (hypertension), high cholesterol, or diabetes
- Lose weight if needed/maintain a healthy body weight
- Eat a healthy, balanced diet
What Are Complications of a Subarachnoid Hemorrhage?
A subarachnoid hemorrhage can lead to complications such as:
- Rebleeding
- The brain aneurysm bursts again
- High risk of permanent disability or death
- Aneurysm repair is needed as soon as possible
- Vasospasm (also called delayed cerebral ischemia)
- A blood vessel spasms, causing it to narrow
- The blood supply to the brain becomes critically low, resulting in brain damage
- Symptoms include increased drowsiness, which can lead to a coma
- Medications such as nimodipine (Nymalize) may be prescribed to help prevent and treat vasospasm
- Hydrocephalus
- Build-up of fluid on the brain, which increases intracranial pressure and can lead to brain damage
- Symptoms may include including headache, vomiting, blurry vision, and difficulty walking
- May be treated with a lumbar puncture or a temporary tube surgically implanted into the brain to drain excess fluid
- Long-term complications
From 
Brain and Nervous System Resources
Image source: iStock Images
https://www.nhs.uk/conditions/subarachnoid-haemorrhage/
https://www.hopkinsmedicine.org/health/conditions-and-diseases/subarachnoid-hemorrhage