Subarachnoid Hemorrhage (SAH)


What is subarachnoid hemorrhage (SAH)?

Subarachnoid hemorrhage (SAH) is a type of stroke. Head trauma is the most common cause.

In patients without head trauma, SAH is most commonly caused by a brain aneurysm. A brain aneurysm is a ballooning of an artery in the brain that can rupture and bleed into the space between the brain and the skull.

Risk factors for developing an aneurysm include:

Symptoms and Causes

What are the symptoms of subarachnoid hemorrhage (SAH)?

Most subarachnoid hemorrhages caused by brain aneurysms do not cause symptoms until they rupture. A ruptured brain aneurysm is an emergency and 9-1-1 should be called immediately. Symptoms of a ruptured brain aneurysm include:

  • Sudden worst headache of life
  • Associated neck or back pain
  • Nausea and vomiting
  • Decreased responsiveness
  • Sudden weakness
  • Dizziness
  • Seizure

Diagnosis and Tests

How is a subarachnoid hemorrhage (SAH) diagnosed?

  • Computerized tomography (CT scan) of the brain is a simple, effective way to see a subarachnoid hemorrhage. Another type of CT scan, CT angiography (CTA), visualizes blood vessels using contrast material injected intravenously (through a vein). Sometimes, a CT scan may miss a very small subarachnoid hemorrhage, or one that has occurred a week or two ago. Other tests may be ordered to detect a subarachnoid hemorrhage if a CT scan is negative. These tests include:
  • Lumbar puncture. A small needle is placed in the lowest part of the back to obtain cerebrospinal fluid, the fluid that bathes our brain and spinal cord. The fluid is tested for subarachnoid hemorrhage.
  • Magnetic resonance imaging (MRI) of the brain. This imaging test can show if there has been “subacute” blood, or bleeding in the brain, in the recent past.

Other tests given after subarachnoid hemorrhage (SAH) is diagnosed

The hospital care following the diagnosis of subarachnoid hemorrhage focuses on both discovering and treating the cause of the SAH, as well as managing its complications.

Aneurysm detection

Since brain aneurysms cause over 80 percent of nontraumatic subarachnoid hemorrhages, it is very important to image the brain’s arteries and then treat the aneurysm.

The most common test performed to best see the brain’s blood vessels is a cerebral angiogram. A catheter is placed in the main artery in the groin (femoral artery) or wrist (radial artery). Through this a thinner catheter is advanced through the body’s arterial system into the neck. Contrast material is then injected and the X-ray pictures capture the blood flowing in the brain’s arteries and brains.

Occasionally, subarachnoid hemorrhages may be caused by other brain or spine vascular lesions. An MRI of the brain and/or spine may be ordered if a cerebral angiogram does not demonstrate a brain aneurysm.

A much rarer vascular cause for subarachnoid hemorrhage, benign perimesencephalic SAH is a type of SAH in which no vascular lesion is found on imaging. Some theories regarding cause include bleeding from a vein or from a blood clot in the blood vessel wall.

Preventing aneurysm rebleeding

Once an aneurysm has ruptured, there is an increased chance that it can rebleed. Brain aneurysm rebleeding is dangerous and can be fatal. The chance of rebleeding can be reduced by:

  • Securing the aneurysm
  • Controlling blood pressure
  • Correcting any bleeding disorder or reversing certain types of blood thinning medications.

Management and Treatment

How is SAH from brain aneurysm treated?

Securing a brain aneurysm

There are several ways to treat a brain aneurysm, including open surgery or endovascular treatment. Endovascular treatment of an aneurysm is a minimally invasive option using cerebral angiography to access the aneurysm. The decision on which treatment is best depends on the characteristics of the aneurysm and overall health of the patient. The surgical team will discuss these options and recommendations for which treatment is best.

Open surgical techniques: clipping or bypass

Clipping. One treatment for securing a brain aneurysm is through microsurgical clipping. This surgery requires a craniotomy. A craniotomy is performed by making an incision on the head and temporarily removing a small portion of skull.

Clipping treatment for brain aneurysm | Cleveland Clinic

After the brain is exposed, the surgical team uses an intraoperative microscope to dissect through the brain to access the aneurysm. Once the aneurysm is visualized, a small clip is placed around the base, or neck, of the aneurysm. The skull portion is replaced and fastened with plates and screws, and the incision is closed.

  • Vessel bypass. If the aneurysm is a type that won’t allow straightforward microsurgical clipping, vessel bypass may be done. After a craniotomy is performed and the aneurysm is accessed, another blood vessel may be sewn onto the artery past the aneurysm to make sure blood flows well to the brain after the aneurysm is secured. Blood vessels that may be used include another artery within the brain itself, a scalp artery, or arteries that are taken from the arm or veins in the leg. All of the metal used in open surgery is MRI safe and made of titanium or titanium alloys.

Endovascular surgical techniques: coiling and/or stenting/flow diversion

Endovascular treatment is a minimally invasive method to treat brain aneurysms.

  • Coiling. A cerebral angiogram is performed, passing a catheter into the brain. When an aneurysm is coiled, a catheter is extended into the base of the aneurysm and platinum coils are released into the aneurysm. These coils fold in such a way as to fill the aneurysm. The coils then form a clot to prevent any further blood flow into the aneurysm. There are times when a stent may be used to support the coils remaining in the aneurysm and protect normal blood flow through the artery.

Coiling to treat brain aneurysm | Cleveland Clinic

  • Stenting/flow diversion. A newer device used to treat aneurysms is called a flow diversion device. These special types of stents (tubes) are placed across the base of the aneurysm and reduce blood flow into the aneurysm, causing a clot to form in the aneurysm and eventually cure it. A patient who receives a stent or flow diversion device is also prescribed medications to prevent clots from forming within the stent of the flow diversion device. Specific medications and duration of treatment may vary.

How are possible complications from subarachnoid hemorrhage from brain aneurysm treated?

Brain swelling and hydrocephalus

Complications from SAH can include brain swelling and hydrocephalus. Bleeding from a subarachnoid hemorrhage can cause swelling of the brain, which can be life threatening. Monitoring of the brain’s pressure is important for any patient with symptoms of significant brain swelling. Medications can be used to treat brain swelling.

Bleeding can also cause hydrocephalus, an excess of the cerebrospinal fluid (CSF) in the brain. Our brains float in a bath of CSF. This fluid is made primarily in spaces in the center areas of our brain called ventricles. The bleeding that occurs in SAH can cause an obstruction in the ventricles that blocks the fluid from passing through and these spaces get larger.

This bleeding can also interfere with the brain’s ability to reabsorb the fluid normally. Hydrocephalus can be potentially dangerous if untreated. The treatment for hydrocephalus is to drain the excess fluid (see below).

External ventricular drain (EVD). An external ventricular drain, or EVD, is a drain placed in the ventricle of the brain to serve both as a monitor for intracranial pressure (ICP), as well as a treatment for brain swelling and hydrocephalus. An EVD is placed by drilling a small hole in the skull and passing the catheter into one of the ventricles in the brain (shaded area of brain in illustration). Most patients have an EVD for 1 to 2 weeks. As the blood in the cerebrospinal fluid (CSF) clears, the team will attempt to “wean” the EVD by draining less fluid and determining if the patient can circulate and absorb their CSF normally.

External ventricular drain | Cleveland Clinic

Shunt surgery. Most patients need an EVD temporarily until the brain can resume the regular flow and absorption of CSF. For some, the blood interferes with brain's normal absorption of CSF. If this occurs, a surgery called a shunt placement is recommended. A shunt surgery permanently places a drain from the ventricles into the peritoneal cavity of the abdomen to treat hydrocephalus.


A seizure is an over-excitability of a brain cell’s electrical discharges. A patient can have a seizure that causes shaking of one part or all of the body. Or “silent” seizures may occur, which may cause sleepiness but are not otherwise clinically detected.

After a subarachnoid hemorrhage, a patient may have a seizure from the sudden increase in brain pressure, or due to the bleeding in the brain irritating the brain cells. Patients are treated with medications to prevent them from seizing at the onset of the hemorrhage. They may also require longer-term therapy based upon the treatment and whether or not they actually seize.

Some patients require monitoring for seizures with an electroencephalogram (EEG). An EEG is a test that uses electrodes temporarily attached to the scalp that show abnormalities in the brain’s electrical activity.

Vasospasm and treatment methods

After an aneurysm ruptures, the brain’s arteries may begin to narrow due to the presence of the blood and inflammation. This condition is called vasospasm. If the vasospasm is significant (called clinical vasospasm), a patient may develop neurologic changes and even suffer an ischemic stroke.

The peak period for development of vasospasm occurs between the 7th and 10th days after the aneurysm bleeds, but may extend to 14 days or longer after the hemorrhage.

  • Close neurologic monitoring is key in monitoring for vasospasm. Other tests such as transcranial Doppler (TCD) may be used in monitoring for vasospasm.
  • The medication nimodipine is thought to improve outcomes from vasospasm following subarachnoid hemorrhage.
  • Maintaining hydration is key and is monitored closely.

If a patient develops clinical vasospasm a number of medical measures are put in place to optimize oxygenated blood flow delivery to the brain in the intensive care unit. A cerebral angiogram may also be needed to treat vasospasm.

  • Patients with severe brain swelling, or those who cannot undergo an external ventricular drain (EVD), may benefit from another type of brain pressure monitor. The intraparenchymal (ICP) monitor is a tiny catheter advanced into the brain after a small hole is drilled through the skull and a bolt is secured to the skull.
  • Patients who are at risk for vasospasm and are in a coma or have a significantly depressed neurologic exam may also receive an intraparenchymal brain tissue oxygen monitor. Similar to the ICP monitor, this tiny brain tissue oxygen monitor is advanced into the brain through a small hole drilled through the skull.

How long are hospital stays for subarachnoid hemorrhage (SAH)?

Length of stay in the hospital varies based on patients’ clinical status. Most patients are admitted in the hospital anywhere from 10 to 20 days based on their condition, need for rehabilitation, and the presence and/or course of vasospasm. Patients diagnosed with benign perimesencephalic subarachnoid hemorrhage are usually discharged within 1 week.

Living With

What follow up is needed after subarachnoid hemorrhage (SAH)?

Patients are often seen in outpatient neurosurgical follow up after 1 month with a CT brain to evaluate neurologic recovery and evaluate for delayed hydrocephalus. Hydrocephalus can occasionally occur weeks after a hemorrhage if there is slow imbalance between the brain’s production and reabsorption of cerebrospinal fluid.

Additional follow up with aneurysm imaging depends on the aneurysm’s initial treatment and the appearance of the aneurysm at discharge. It is important to maintain a long-term relationship with the cerebrovascular neurosurgical group for aneurysm monitoring.

What is recovery after a subarachnoid hemorrhage (SAH)?

Recovery after a subarachnoid hemorrhage widely varies based upon the cause and the extent of neurologic injury. Most patients with subarachnoid hemorrhage from an aneurysm require inpatient rehabilitation after the hospital stay, as well as outpatient therapy for months following. Feeling sad or anxious about the hospital stay or the illness is common. It is important to discuss these feelings with friends and family, as well as the medical team.


Cleveland Clinic Stroke Support Group. The Cleveland Clinic offers a stroke support group which meets regularly. For more information about the support group, click link above or call 216-636-0450.

Annual Cleveland Clinic Brain Aneurysm Awareness Run/Walk. The Cleveland Clinic hosts an annual brain aneurysm charity walk and run. This is also a great way for patients and families to celebrate survivorship and honor patients. All proceeds benefit patient resources and aneurysm research. For more information, click link above or call 216-623-9933.

Outside brain aneurysm support information

  • Brain Aneurysm Foundation is a nonprofit organization offering educational materials and support group information.
  • The Bee Foundation is a nonprofit organization advocating for brain aneurysm research.
  • Joe Niekro Foundation is a nonprofit organization offering educational materials, caregiver information, and support group information.
  • Lisa Colagrossi Foundation is a nonprofit organization promoting community awareness and education about brain aneurysms.

Last reviewed by a Cleveland Clinic medical professional on 06/18/2018.

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy