A subarachnoid hemorrhage is bleeding in the space between your brain and the membrane that covers it. Most often, it occurs when a weak area in a blood vessel (aneurysm) on the surface of the brain bursts and leaks. The blood then builds up around the brain and inside the skull. This increases pressure on the brain. It can cause brain cell damage, life-long problems, and disabilities.

When an aneurysm is located in the brain, it's called a cerebral, intracerebral, or intracranial aneurysm. A cerebral aneurysm often develops over a long period of time and may not cause any symptoms before it bursts (ruptures). Most aneurysms develop after age 40.

A subarachnoid hemorrhage may cause a type of stroke called a hemorrhagic stroke. This type of stroke causes bleeding inside the brain. Head trauma is the most common cause of subarachnoid hemorrhage. Most spontaneous, nontraumatic subarachnoid hemorrhages are caused by bleeding after a brain aneurysm rupture. It is different from an ischemic stroke, which is caused by a blood clot.

This bleeding may go through the brain tissue and leak into the area outside the brain. This area is called the subarachnoid space. This can be life-threatening. The blood from the hemorrhage can compress or displace vital brain tissue. A severe hemorrhage can cause a coma. Or it can leave you paralyzed.

Common symptoms include:

• Severe headache, the worst headache pain you've ever had that feels different from other headaches
• Loss of consciousness (may be brief or prolonged)
• Double vision
• Nausea or vomiting
• Trouble speaking
• Drooping eyelid
• Confusion and trouble concentrating
• Sensitivity to light
• Neck stiffness
• Neck pain
• Seizures

These symptoms may look like other health problems. Get medical care right away if you have these symptoms.

A brain aneurysm can lead to a subarachnoid hemorrhage. A brain aneurysm can cause these symptoms:

• Pain around the eye
• Changes in your vision, including double vision
• Dilated pupils
• Weakness or numbness on one side of your body
• Loss of hearing or trouble with balance
• Seizures
• Trouble with memory

If you have symptoms of a subarachnoid hemorrhage, you may need several tests for a diagnosis:

• CT scan. This test uses X-rays and a computer to make horizontal (axial) images of the brain. CT scans are more detailed than general X-rays.
• MRI scan. This test uses large magnets, radio waves, and a computer to make detailed images of the brain. It doesn't use X-rays.
• Angiogram. During this test, contrast dye is injected in the blood vessel. Then X-rays are taken to assess blood flow through them.
• Spinal tap. In this test, a special needle is placed into the low back, into the spinal canal. The pressure in the spinal canal and brain can be measured. A small amount of cerebrospinal fluid (CSF) can be removed. The CSF is checked for blood.

A diagnosis of a cerebral aneurysm isn't usually made until a subarachnoid hemorrhage has already occurred.

A subarachnoid hemorrhage is a medical emergency. Immediate treatment is needed to help reduce the risk for lifelong brain damage. The main goal is to stop the bleeding and prevent rebleeding. Medicines may be started to prevent vasospasm and control high arterial pressure. Other medicines, such as blood thinners (anticoagulants), will be stopped. Often, a doctor may do surgery to place a small clip or stent on the blood vessel. This is to stop blood from leaking into the brain.

Some types of aneurysms can be treated with a detachable endovascular coil. This procedure is done by either a radiologist or a neurosurgeon. It is done with a tiny cut (incision) in your groin. A thin tube called a catheter is put through the incision into the artery in your leg. It is pushed up to the artery in your head that is bleeding. Recovery time from this type of treatment is much shorter than traditional surgery. But not all aneurysms can be treated this way. Your doctor can determine if you are a candidate for this treatment after doing an angiogram.

Part of the long-term treatment of a subarachnoid hemorrhage includes addressing any risk factors that may have helped trigger the hemorrhage. One of the biggest risk factors is smoking. If you smoke, it's important to try to quit. Talk with your doctor if you need help quitting. They can offer advice, support, and resources. Gaining better control of conditions, such as diabetes, high cholesterol, or high blood pressure, is also important. Keeping a healthy body weight and eating a healthy diet can also reduce your risk.

After a subarachnoid hemorrhage, serious complications can occur. Swelling in the brain (hydrocephalus) is one of the possible problems. It's caused by the buildup of CSF and blood between the brain and skull. This can increase the pressure on the brain. A subarachnoid hemorrhage can also irritate and damage the brain's other blood vessels, causing them to tighten. This reduces blood flow to the brain. As blood flow becomes affected, another stroke can happen. This can lead to even more brain damage. In serious cases, the bleeding may cause lifelong brain damage, paralysis, or coma.

The sooner the bleeding in the brain is controlled, the better the outlook. Get emergency medical care if you have any signs, such as:

• Seizures
• Severe headache; the worst headache pain that you have ever had
• Nausea and vomiting with the headache
• Double vision
• Neck stiffness
• Trouble speaking
• Drooping eyelid
• Confusion and trouble concentrating
• Sensitivity to light with the headache

• A subarachnoid hemorrhage means that there is bleeding in the space that surrounds the brain.
• It is life-threatening and a medical emergency.
• It often occurs in people older than age 40.
• One of the first symptoms is often having a severe headache. This is often followed by loss of consciousness.
• Get medical care right away if any of the above symptoms affect you or a loved one.

Tips to help you get the most from a visit to your doctor:

• Know the reason for your visit and what you want to happen.
• Before your visit, write down questions you want answered.
• Bring someone with you to help you ask questions and remember what your doctor tells you.
• At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your doctor gives you.
• Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are and when you should report them to your doctor.
• Ask if your condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if you do not take the medicine or have the test or procedure.
• If you have a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your doctor if you have questions, especially after office hours and on weekends and holidays.