Subarachnoid Hemorrhage

What is subarachnoid hemorrhage?

A subarachnoid hemorrhage is bleeding into the space that surrounds the brain. The brain is covered by several thin layers of tissue called meninges. Between two of these layers lies the subarachnoid space, which is normally filled with cerebrospinal fluid — the clear liquid that cushions and protects the brain and spinal cord. When a blood vessel on the surface of the brain leaks or bursts, blood spills into this space. Doctors classify this event under the medical code ICD-10 I60.9 when the exact source of the bleeding has not yet been specified.

Understanding what is subarachnoid hemorrhage begins with recognizing that it is a type of stroke. Unlike the more common ischemic stroke, which happens when a blood clot blocks blood flow to the brain, a subarachnoid hemorrhage is a hemorrhagic stroke — one caused by bleeding. The blood that escapes into the subarachnoid space irritates brain tissue, raises pressure inside the skull, and can interfere with the normal flow of cerebrospinal fluid.

Subarachnoid hemorrhage can affect people of any age, although it most often occurs in middle-aged adults. It appears to be somewhat more common in women than in men. It is a medical emergency in every case: rapid recognition and treatment can strongly influence how well a person recovers. In many hospital systems, including the neurology and neurosurgery departments of groups such as Acibadem, care for this condition is coordinated between emergency medicine, neurosurgery, and intensive care teams.

Symptoms of subarachnoid hemorrhage

The hallmark of subarachnoid hemorrhage symptoms is a sudden, extremely severe headache. Many patients describe it as the worst headache of their lives, and doctors often call it a “thunderclap headache” because it reaches maximum intensity within seconds to a minute. This headache is different from an ordinary tension headache or migraine, which usually build up gradually.

Common symptoms include:

• Sudden, severe headache — often described as explosive or unlike any previous headache
• Neck stiffness or neck pain — caused by blood irritating the membranes around the brain and spinal cord
• Nausea and vomiting — frequently accompanying the headache
• Sensitivity to light (photophobia)
• Brief loss of consciousness or fainting at the moment the bleeding starts
• Confusion, drowsiness, or reduced alertness
• Seizures — sudden episodes of abnormal electrical activity in the brain, which may cause shaking or loss of awareness
• Blurred or double vision, or a drooping eyelid
• Weakness or numbness on one side of the body in some cases

Symptoms can vary depending on how the bleeding developed. In some people, a smaller “warning leak” — sometimes called a sentinel headache — occurs days or weeks before a major rupture. This warning headache may be severe but short-lived, and it is easy to dismiss. Recognizing it and seeking care promptly can make a meaningful difference, because doctors may be able to find and treat the weakened blood vessel before a larger bleed occurs.

In the days after the initial bleed, new or worsening symptoms may appear. These can be caused by complications such as vasospasm (narrowing of the brain’s blood vessels), hydrocephalus (a buildup of cerebrospinal fluid that raises pressure in the skull), or rebleeding. A person recovering in the hospital who becomes more confused, weaker, or harder to wake needs immediate medical assessment.

When the hemorrhage follows a head injury rather than a burst blood vessel, symptoms may overlap with those of the injury itself — headache, confusion, drowsiness, and vomiting — which is one reason doctors monitor head-injury patients closely.

Causes and risk factors

The most frequent subarachnoid hemorrhage causes fall into two broad groups: spontaneous bleeding from a weakened blood vessel, and bleeding caused by head trauma.

Ruptured brain aneurysm. The leading cause of spontaneous subarachnoid hemorrhage is a ruptured cerebral aneurysm. An aneurysm is a weak, bulging spot in the wall of an artery, somewhat like a thin patch on a balloon. Aneurysms often develop at branch points of the arteries at the base of the brain. Many people live with small aneurysms that never cause problems, but when an aneurysm bursts, blood is released directly into the subarachnoid space.

Head trauma. Injuries from falls, road accidents, or blows to the head can tear small blood vessels on the surface of the brain, producing a traumatic subarachnoid hemorrhage. This is a common finding after significant head injury.

Other, less common causes include:

• Arteriovenous malformation (AVM) — an abnormal tangle of blood vessels in or near the brain that a person is usually born with
• Bleeding disorders or the use of blood-thinning medications (anticoagulants)
• Inflammation or infection of blood vessels in rare cases
• Use of stimulant drugs, such as cocaine, which can sharply raise blood pressure

Several factors are known to increase the risk of aneurysm formation and rupture:

• High blood pressure (hypertension) — sustained pressure stresses artery walls
• Smoking — one of the strongest modifiable risk factors
• Heavy alcohol use
• Family history — having close relatives who had brain aneurysms or subarachnoid hemorrhage raises risk
• Certain inherited conditions, such as polycystic kidney disease and some connective tissue disorders
• Age and sex — risk rises with age, and women are affected somewhat more often than men

Having a risk factor does not mean a person will develop the condition, and some people who suffer a subarachnoid hemorrhage have no identifiable risk factors at all. However, controlling blood pressure and stopping smoking are widely accepted ways to reduce risk.

Diagnosis

Subarachnoid hemorrhage diagnosis begins with the patient’s story and a physical and neurological examination. Because the sudden severe headache is so characteristic, doctors take any “worst headache of my life” description very seriously and move quickly to imaging.

CT scan of the head. A computed tomography (CT) scan — a fast X-ray-based imaging test — is usually the first investigation. Fresh blood in the subarachnoid space typically shows up clearly on CT, especially when the scan is performed soon after symptoms begin. The sensitivity of CT is highest in the first hours after the bleed and gradually decreases as the blood is reabsorbed.

Lumbar puncture (spinal tap). If the CT scan is normal but the doctor still strongly suspects a hemorrhage, a lumbar puncture may be performed. In this test, a thin needle is inserted into the lower back to collect a small sample of cerebrospinal fluid. The presence of blood or blood-breakdown products (which give the fluid a yellowish tint called xanthochromia) supports the diagnosis even when imaging is inconclusive.

Vascular imaging. Once a subarachnoid hemorrhage is confirmed, doctors need to find the source of the bleeding. Options include:

• CT angiography (CTA) — a CT scan performed with contrast dye injected into a vein to outline the brain’s arteries
• Catheter cerebral angiography — a more detailed test in which a thin tube (catheter) is guided through the blood vessels and dye is injected directly into the brain arteries; this is often considered the most definitive test for detecting aneurysms
• Magnetic resonance imaging (MRI) and MR angiography — sometimes used, particularly when the bleed is older or the diagnosis is uncertain

Doctors also grade the severity of the hemorrhage using clinical scales that consider the patient’s level of consciousness and neurological function. These grades help the care team plan treatment and monitor progress, though they are estimates rather than predictions for any individual.

Treatment options

Subarachnoid hemorrhage treatment has three main goals: stabilize the patient, stop or prevent further bleeding, and prevent or manage complications. Treatment almost always takes place in a hospital, usually in an intensive care or specialized neurological unit.

Emergency stabilization

Initial care focuses on protecting breathing and circulation, controlling severe pain, managing blood pressure carefully, and treating seizures if they occur. Patients are monitored closely, because their condition can change quickly in the first days after the bleed.

Securing a ruptured aneurysm

If an aneurysm caused the hemorrhage, sealing it off is a priority, because a ruptured aneurysm can bleed again — and rebleeding is one of the most dangerous early complications. Two established approaches are used:

• Endovascular coiling. A minimally invasive procedure in which a specialist guides a thin catheter through the blood vessels (usually starting in the groin or wrist) up to the aneurysm, then releases tiny platinum coils inside it. The coils encourage clotting within the aneurysm, sealing it from the circulation. Related endovascular techniques, such as stents or flow-diverting devices, may be used in selected cases.
• Surgical clipping. An open operation in which a neurosurgeon places a small metal clip across the neck of the aneurysm, cutting it off from blood flow. This requires a craniotomy — the temporary removal of a small section of the skull to reach the brain.

The choice between coiling and clipping depends on the aneurysm’s size, shape, and location, the patient’s overall condition, and the expertise available. A multidisciplinary team typically weighs the options; neither approach is universally “better,” and your doctors will explain which is suitable in a particular situation.

Medications

Medications commonly used after subarachnoid hemorrhage include:

• Nimodipine, a calcium channel blocker that is widely used to reduce the risk of brain injury from vasospasm — the delayed narrowing of brain arteries that can occur in the days after the bleed
• Pain relievers chosen carefully to control headache without masking neurological changes
• Anti-seizure medications in some patients
• Stool softeners and other supportive medications to avoid straining, which can raise pressure in the head

Managing complications

If hydrocephalus develops — a buildup of cerebrospinal fluid that raises pressure inside the skull — doctors may place a temporary drain (an external ventricular drain) to relieve the pressure. Some patients later need a permanent shunt, a thin tube that diverts excess fluid to another part of the body. Vasospasm is monitored with repeated examinations and imaging, and may be treated with medications or endovascular procedures if it threatens blood flow to the brain.

Watchful waiting and non-aneurysmal cases

Not every subarachnoid hemorrhage requires a procedure. In some patients — for example, certain traumatic hemorrhages or bleeds with no aneurysm found on angiography — treatment may consist of close observation, blood pressure control, and supportive care while the blood is gradually reabsorbed. Doctors often repeat vascular imaging after some time to make sure no hidden aneurysm was missed.

Rehabilitation

After the acute phase, many patients benefit from rehabilitation, which can include physical therapy, occupational therapy, speech therapy, and neuropsychological support, depending on the effects of the hemorrhage. At centers such as Acibadem, rehabilitation planning generally begins during the hospital stay and continues after discharge.

Living with subarachnoid hemorrhage and outlook

The outlook after a subarachnoid hemorrhage varies widely. It depends on the cause and severity of the bleed, how quickly treatment was received, the person’s age and general health, and whether complications developed. Honesty matters here: subarachnoid hemorrhage is a serious condition, and some patients do not survive it or are left with lasting disability. At the same time, many people — particularly those with smaller bleeds who were treated promptly — recover well and return to independent lives.

Recovery is often gradual and can take months. Common challenges during recovery include:

• Fatigue — often profound in the early months and slow to improve
• Headaches that persist for a period after the bleed
• Memory, concentration, and thinking difficulties
• Mood changes, including anxiety, depression, and irritability
• Sleep disturbances

These effects can occur even when scans look reassuring, and they often improve over time, although the pace differs from person to person. Support from family, employers, and mental health professionals can be valuable during this period. Many patients gradually return to work, sometimes in stages.

Long-term follow-up usually includes managing blood pressure, stopping smoking, limiting alcohol, and attending scheduled imaging appointments to check that a treated aneurysm remains sealed and to look for any new aneurysms, particularly in people with a family history. Your medical team can advise on driving, exercise, and travel, since guidance depends on individual circumstances and local regulations.

Frequently asked questions

What is subarachnoid hemorrhage in simple terms?

It is bleeding into the fluid-filled space that surrounds the brain, most often caused by a burst aneurysm (a weak, bulging spot on a brain artery) or by a head injury. Because the escaped blood irritates the brain and raises pressure inside the skull, it is always treated as a medical emergency.

How serious is a subarachnoid hemorrhage?

It is a life-threatening condition. Some people do not survive the initial bleed or its complications, while others recover well, especially when the hemorrhage is recognized quickly and treated promptly. The severity of the bleed, the person’s condition on arrival at the hospital, and whether complications develop all influence the outcome, so no general statement applies to every patient.

Can a subarachnoid hemorrhage heal on its own?

The blood itself is gradually reabsorbed by the body over days to weeks. However, if a ruptured aneurysm caused the bleeding, it will not heal reliably on its own and carries a real risk of bleeding again, which is why doctors usually recommend a procedure to seal it. Some smaller or traumatic bleeds may be managed with careful monitoring alone, but that decision belongs to the treating team.

What does the headache of a subarachnoid hemorrhage feel like?

Patients typically describe a sudden, explosive headache that reaches its worst intensity within seconds — often called a thunderclap headache — and many say it is the worst headache they have ever experienced. It is frequently accompanied by neck stiffness, nausea, vomiting, or fainting. Any headache like this warrants emergency evaluation, even if it eases on its own.

How long does recovery from a subarachnoid hemorrhage take?

Recovery timelines vary widely. Some people improve substantially within weeks, while others need many months of rehabilitation, and some effects — such as fatigue or difficulty concentrating — can linger longer. Doctors generally describe recovery as gradual, and follow-up appointments help track progress and adjust rehabilitation plans.

Can a subarachnoid hemorrhage happen again?

It can, particularly if a ruptured aneurysm is not secured, or if a person has additional aneurysms or ongoing risk factors such as uncontrolled high blood pressure or smoking. Securing the aneurysm with coiling or clipping greatly reduces the risk of rebleeding from that aneurysm, and follow-up imaging helps confirm that the repair remains effective.

Is subarachnoid hemorrhage the same as a stroke?

It is one type of stroke. Most strokes are ischemic, caused by a blocked artery, while a subarachnoid hemorrhage is a hemorrhagic stroke, caused by bleeding around the brain. The two types have different causes and treatments, which is why rapid diagnosis with imaging is so important.

When to see a doctor

Subarachnoid hemorrhage is an emergency. Call your local emergency number or go to the nearest emergency department immediately if you or someone near you experiences any of the following:

• A sudden, severe headache that peaks within seconds to a minute — especially if it feels like the worst headache of your life
• Headache with neck stiffness, vomiting, or sensitivity to light
• Loss of consciousness, fainting, or a seizure, particularly alongside a severe headache
• Sudden confusion, drowsiness, or difficulty waking someone up
• Sudden weakness, numbness, vision changes, or trouble speaking
• A severe headache after a head injury, or worsening drowsiness in the hours or days following one

You should also seek prompt (non-emergency) medical advice if you have a strong family history of brain aneurysms or subarachnoid hemorrhage, or if you experienced a brief but unusually severe headache recently, even if it has resolved. A doctor can assess whether screening or further tests are appropriate for your situation. Acting quickly on warning signs is one of the most important steps anyone can take, because early diagnosis and treatment of subarachnoid hemorrhage often shape the outcome.