Subarachnoid hemorrhage


Subarachnoid hemorrhage is bleeding in the area between the brain and the thin tissues that cover the brain. This area is called the subarachnoid space.

Alternative Names

Hemorrhage - subarachnoid


Subarachnoid hemorrhage can be caused by:

Subarachnoid hemorrhage caused by injury is often seen in the elderly who have fallen and hit their head. Among the young, the most common injury leading to subarachnoid hemorrhage is motor vehicle crashes.

Risks include:

A strong family history of aneurysms may also increase your risk.


The main symptom is a severe headache that starts suddenly (often called thunderclap headache). It is often worse near the back of the head. Many people often describe it as the "worst headache ever" and unlike any other type of headache pain. The headache may start after a popping or snapping feeling in the head.

Other symptoms:

Other symptoms that may occur with this disease:

Exams and Tests

Signs include:

If your doctor thinks you have a subarachnoid hemorrhage, a head CT scan (without contrast dye) will be done right away. In some cases, the scan is normal, especially if there has only been a small bleed. If the CT scan is normal, a lumbar puncture (spinal tap) may be done.

Other tests that may be done include:


The goals of treatment are to:

Surgery may be done to:

If the person is critically ill, surgery may have to wait until the person is more stable.

Surgery may involve:

If no aneurysm is found, the person should be closely watched by a health care team and may need more imaging tests.

Treatment for coma or decreased alertness includes:

A person who is conscious may need to be on strict bed rest. The person will be told to avoid activities that can increase pressure inside the head, including:

Treatment may also include:

Outlook (Prognosis)

How well a person with subarachnoid hemorrhage does depends on a number of different factors, including:

Older age and more severe symptoms can lead to a poorer outcome.

People can recover completely after treatment. But some people die even with treatment.

Possible Complications

Repeated bleeding is the most serious complication. If a cerebral aneurysm bleeds for a second time, the outlook is much worse.

Changes in consciousness and alertness due to a subarachnoid hemorrhage may become worse and lead to coma or death.

Other complications include:

When to Contact a Medical Professional

Go to the emergency room or call the local emergency number (such as 911) if you have symptoms of a subarachnoid hemorrhage.


Identifying and successfully treating an aneurysm can prevent subarachnoid hemorrhage.


Mayer SA. Hemorrhagic cerebrovascular disease. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 408.

Reinhardt MR. Subarachnoid hemorrhage. J Emerg Nurs. 2010;36:327-329. PMID: 20624566

Tateshima S, Duckwiler G. Vascular diseases of the nervous system: intracranial aneurysms and subarachnoid hemorrhage. In: Daroff RB, Fenichel GM, Jankovic J, Mazziotta JC. Bradley's Neurology in Clinical Practice. 6th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 51C.