Subarachnoid Hemorrhage

A subarachnoid hemorrhage is bleeding between the arachnoid mater and the pia mater. These are the tissues that cover the brain and its blood vessels and contain cerebrospinal fluid. Treatment for subarachnoid hemorrhage varies by case—and particularly according to the cause of the hemorrhage. Surgical options when an aneurysm is present include clipping, coiling, flow diversion, embolization, or resection. Surgical treatment for a hemorrhage caused by arteriovenous malformation (AVM) may include embolization, resection, or radiosurgery.

A subarachnoid hemorrhage is a rare form of stroke, accounting for about 3 percent of cases. It is a medical emergency, and the goal of treatment is to secure the bleeding site as soon as possible. Ruptured aneurysms tend to bleed again within hours or a few days after initial bleeding. Efficient evaluation and treatment decisions are best made by a specialized, experienced stroke team at a comprehensive stroke center like the one at Columbia University Irving Medical Center/NewYork-Presbyterian Hospital.


The most common symptom of a subarachnoid hemorrhage is a sudden, severe headache that becomes worse over a matter of seconds. It is sometimes called a “thunderclap” headache or described as “the worst headache” of someone’s life. The headache is sometimes followed by a loss of consciousness lasting minutes, hours or days. Vision changes, confusion, nausea and vomiting may also be present. Seizures are possible. These symptoms indicate a medical emergency.

In some cases, a set of prodromal symptoms may occur an average of 10 to 20 days before the hemorrhage itself. These symptoms include headache, dizziness, vision changes, eye pain, seizures, or changes in the ability to move some part of the body. These symptoms are not sufficient by themselves to diagnose an impending subarachnoid hemorrhage; they can also be caused by many other conditions. But they may prompt further urgent investigation that reveals the risk for hemorrhage, especially in patients known to be at risk.


The symptoms of a subarachnoid hemorrhage are usually very classic. The symptoms alone strongly suggest (but cannot confirm) the diagnosis.

To confirm the diagnosis, an emergency CT scan is performed. Also known as a computed tomography scan or a CAT scan, a CT scan uses a computer and X-rays to form detailed images of the body’s structures.

If no subarachnoid hemorrhage is found on CT scan in a patient whose symptoms suggest one, a lumbar puncture may be performed. In this test, a doctor uses a needle to remove some fluid from around the spine in the lower back. Analysis of this fluid can either indicate subarachnoid hemorrhage or suggest another condition.

When a subarachnoid hemorrhage is found, doctors may next perform an angiogram. In an angiogram, a special dye is injected into the bloodstream through a plastic tube placed in a large artery in the patient’s leg. As the dye travels through the bloodstream, it allows doctors to create detailed images of blood flow—including aneurysms and AVMs. An angiogram provides information about the size, location, shape, and blood flow of the lesion causing the hemorrhage.

Subarachnoid hemorrhages are emergencies, and every case is different. Doctors weigh many complex factors as they decide which tests to perform and when.

Risk Factors

The most common cause of a subarachnoid hemorrhage is an aneurysm that ruptures. Aneurysms can be present at birth or can develop later in life due to high blood pressure, smoking, trauma, or other factors. An aneurysm can rupture at any age, but the event is most common between the ages of 40 and 65. An aneurysm that leaks small amounts of blood (called sentinel leaks) in advance of rupturing may cause some of the prodromal symptoms described above.

Another cause of subarachnoid hemorrhage is an arteriovenous malformation. These malformations are present at birth but may cause no symptoms until they rupture. Occasionally they grow large enough to produce a mass effect. Arteriovenous malformations large enough to exert a mass effect may cause some of the prodromal symptoms described above.


Prompt treatment at a comprehensive stroke center can maximize a patient’s chances of achieving the best possible outcome.

Treatment varies by case. In general, surgical treatment options for an aneurysm include clipping, coiling, flow diversion, embolization, or resection. Surgical treatment options for AVM include embolization, resection, or radiosurgery.

  • Clipping: Using an open surgical procedure to place a clip that squeezes the aneurysm’s blood supply closed with an open surgical procedure
    • Coiling: Using a minimally invasive radiology procedure to fill the aneurysm with tiny metal coils that cause blood to clot
    • Flow diversion: Inserting a tube in an artery that directs blood flow past the aneurysm
  • Embolization: Injecting a glue-like substance into the lesion that encourages blood there to clot
    • Resection: Removing the aneurysm or AVM
    • Radiosurgery: Delivering precise beams of radiation that slowly shut down the affected vessels

The selection of and timing for each procedure depends on a great variety of factors and a comprehensive team of open surgeons and endovascular surgeons discuss each case to determine the best treatment for each individual patient.

Doctors must also manage possible complications of subarachnoid hemorrhage. One such complication is vasospasm. For reasons that are not fully understood, vasospasm often occurs 7-9 days after the initial bleed, though it can occur as long as three weeks later. Since vasospasm is a leading cause of poor outcome, patients generally stay in the hospital for up to three weeks after the initial subarachnoid hemorrhage so they can be monitored for vasospasm. Vasospasm can often be treated with medication. If it is resistant to medication, vasospasm may be treated with endovascular techniques. The patient remains in a dedicated Neuro ICU during the at-risk period.

Doctors also monitor patients for hydrocephalus, problems with the lungs or heart, and other conditions that can arise after subarachnoid hemorrhage.