Bleeding in the brain

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What is a subarachnoid haemorrhage?

A subarachnoid haemorrhage is a type of stroke caused by bleeding in and around the brain.

The most common symptom of a subarachnoid haemorrhage is a sudden and very severe headache which has been described as 'like being hit on the head with a shovel’.

Other symptoms can include:

  • being
  • seizures (fits)
  • loss of consciousness
  • sudden death (in about 1 in 10 cases)

Read more about the

symptoms of a subarachnoid haemorrhage


Subarachnoid haemorrhage is a medical emergency that requires immediate treatment.

If you or someone you know thinks a subarachnoid haemorrhage has occurred you should immediately dial 999 for an ambulance.

A person with a subarachnoid haemorrhage will need to be admitted to hospital.

There are two main treatment approaches:

  • using medication to prevent complications (see below)
  • using surgery to repair the source of the bleeding

Read more about

treating a subarachnoid haemorrhage

What causes a subarachnoid haemorrhage?

The majority of subarachnoid haemorrhages are caused when a brain aneurysm bursts open. A

brain aneurysm
is a bulge in a blood vessel caused by a weakness in the blood vessel wall. (The medical term for a burst brain aneurysm is a ruptured intracranial aneurysm.)

The blood from a burst aneurysm can damage brain tissue, while the reduction in blood supply can starve the brain of oxygen causing further damage.

It is not always clear why aneurysms develop in the first place but certain things are known to increase your risk of developing one, including:

Read more about the

causes of a subarachnoid haemorrhage


A subarachnoid haemorrhage can cause both short and long-term complications.

Serious short-term complication include:

  • further bleeding at the site of the aneurysm
  • blood vessels near the site of the aneurysm go into spasm (vasospasm) reducing the blood supply further

Long-term complications include:

  • epilepsy
    – where a person has repeated seizures (fits)
  • problems with certain mental functions such as memory, planning and concentration
  • changes in mood such as

Read more about the

complications of a subarachnoid haemorrhage

Who is affected

Four out of five cases occur in people aged between 40 and 65 years, but it can happen at any age; although it is rare in children.

It is more common in women than men.

Subarachnoid haemorrhages are more common in black people compared to other ethnic groups. This could be because black people are more likely to develop high blood pressure.


The outlook for subarachnoid haemorrhage has improved in the last few decades, and about 65% of patients will survive. However, recovery can be a slow and often frustrating process and it is common to have difficulties with issues such as relationships and resuming day to day activities

Read more about

recovering from a subarachnoid haemorrhage

Haemorrhage To haemorrhage means to bleed or lose blood. Blood Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart. Blood vessels Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are veins, arteries and capillaries. Brain The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses. Tissue Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.

Subarachnoid haemorrhage symptoms

Symptoms of a subarachnoid haemorrhage include:

  • a sudden and severe headache – it has been described as a ‘thunderclap headache’, similar to a sudden hit on the head, resulting in a blinding pain unlike anything ever experienced before
  • stiff neck
  • feeling and being sick
  • loss of consciousness or convulsions (uncontrollable shaking)
  • stroke-like symptoms
    such as slurred speech and weakness on one side of the body

If you (or someone in your care) experience the symptoms above you need immediate emergency medical care. Call for an ambulance.

The symptoms of a subarachnoid haemorrhage are similar to

(an infection of the brain's protective membranes) because in both conditions people experience a severe headache and a stiff neck.

Unlike meningitis, people with a subarachnoid haemorrhage do not usually have a high fever or skin rash. However, both conditions are extremely serious and emergency medical treatment should be sought straightaway in either case.

Causes of subarachnoid haemorrhages

Subarachnoid haemorrhages are mainly caused by aneurysms.


Around 8 out of 10 subarachnoid haemorrhages are caused by

brain aneurysms

It is not known why brain aneurysms (sometimes referred to as “berry aneurysms”) occur, although smoking,

high blood pressure
, family history, excess alcohol, and some rarer conditions such as
autosomal dominant polycystic kidney disease
, increase the risk.

If an aneurysm bursts, a subarachnoid haemorrhage will occur. Not everyone who has an aneurysm will experience a haemorrhage, perhaps only a third of people with intracranial aneurysms will experience a haemorrhage, and many people with an aneurysm will have no symptoms.

The risk of an aneurysm bursting is increased by:

  • smoking
  • excessive alcohol consumption
  • poorly controlled high blood pressure

After it has burst, the aneurysm will often seal itself and the bleeding will stop. However, there is a high risk that without treatment, the aneurysm will burst again and cause more bleeding.

Other causes

Other less common causes of subarachnoid haemorrhages include:

  • arteriovenous malformations – which is where blood vessels develop abnormally
  • severe head injury
  • a brain tumour damaging the blood vessels (both
    brain tumours can cause a subarachnoid haemorrhage)
  • a brain infection, such as
    , damaging the blood vessels
  • fibromuscular dysplasia – which is a rare genetic disorder that can cause narrowing of the arteries
  • Moyamoya disease – another rare condition, thought to be genetic, that causes progressive blockages inside the arteries within the brain
  • the blood vessels inside the brain become inflamed (swollen) which is known as vasculitis; vasculitis can have a wide range of underlying causes such as infection or the immune system attacking healthy tissue

Diagnosing a subarachnoid haemorrhage

If you develop symptoms associated with a subarachnoid haemorrhage, such as a sudden severe headache, you will be admitted to hospital for further testing.

Due to the potentially serious nature of a subarachnoid haemorrhage treatment may be given as a precaution even if the diagnosis is still unconfirmed.

There are four main tests used to confirm (or disprove) a diagnosis of a subarachnoid haemorrhage. These are outlined below.

Computerised tomography (CT) scan

A computerised tomography (CT) scan is like an X-ray, but it uses multiple scans or images to build up a more detailed three-dimensional picture of your brain. The scan can be used to detect the presence and location of blood around your brain and any problems that it may be causing. Sometimes a coloured dye is injected into the blood to help pinpoint the source of the bleeding.

Read more about

CT scans

Lumbar puncture

The brain and spinal column are surrounded by a clear liquid called cerebrospinal fluid. If a subarachnoid haemorrhage has occurred, there will be blood in the fluid. To get a sample of cerebrospinal fluid, a needle is inserted into the lower end of your spine and a sample is drawn off. You may find the procedure a little uncomfortable but you will be given a local anaesthetic to numb the area.

Read more about

lumbar punctures

MRI scan

A magnetic resonance imaging (MRI) scan uses strong magnetic fields and radio waves to produce a detailed image of the inside of the body. The scan can be used to detect problems in the blood vessels and, occasionally, detect the haemorrhage itself.

Read more about

MRI scans

Doppler ultrasound

One of the most serious complications associated with subarachnoid haemorrhage is poor blood supply to the brain, called secondary cerebral ischaemia. This may in part be due to arteries in the brain going into spasm (vasospasm), leading to further loss of blood, brain damage and possibly death. Often, vasospasm causes no immediate symptoms so the condition can go unnoticed.

A Doppler ultrasound is a test that uses ultrasound to monitor the flow of blood in the arteries. Sudden changes in the speed of blood flow would indicate that a cerebral vasospasm has occurred, so immediate treatment would then begin.

Read more

ultrasound scans

Subarachnoid haemorrhage treatment

If you are diagnosed with subarachnoid haemorrhage (or a diagnosis is strongly suspected) you are likely to be transferred to a neurosciences unit, where a range of equipment and treatments can be used to support many of the body's vital functions, such as breathing, blood pressure and circulation.

In more severe cases, you may be transferred to an

intensive care unit (ICU)



To prevent further blockage of the supply of blood to your brain (secondary cerebral ischaemia – read more about the

complications of a subarachnoid haemorrhage
), you will be given a medication called nimodipine to take for three weeks.

Side effects of nimodipine include:

  • sweating and flushing
  • feeling sick
  • swelling of the feet, ankles or legs
  • stomach upset

Pain relief

Medication can be effective in relieving the severe pain of the headache associated with a subarachnoid haemorrhage.

Commonly used pain-relieving medications include morphine and a combination of codeine and paracetamol.

Other medications

Other medications that are sometimes used to treat subarachnoid haemorrhage include:

  • anticonvulsants, such as phenytoin, which are used to prevent seizures (fits)
  • beta-blockers
    , which are a type of medication that can help regulate blood pressure
  • antiemetics, such as promethazine, which can help relieve symptoms of feeling sick and being sick
  • diuretics, such as mannitol, which can help relieve pressure inside the brain


Surgery is usually recommended within the first 24 hours of being admitted to hospital to prevent the burst aneurysm from bleeding again.

Neurosurgical clipping

Neurosurgical clipping is an operation carried out under

general anaesthetic
. A cut is made in your scalp and a small flap of bone is removed to reveal your brain underneath.

When the aneurysm is located, the neurosurgeon (an expert in surgery of the brain and nervous system) will seal it shut using a tiny metal clip. After the bone flap has been replaced, the scalp is stitched together.

Endovascular coiling

Endovascular coiling involves inserting a catheter into an artery in your leg or groin. The tube is guided through the network of blood vessels into your head and finally into the aneurysm.

Tiny platinum coils are then passed through the tube into the aneurysm. The coils block the flow of blood into the aneurysm. Over time this should seal the aneurysm off from the main artery to prevent it from rupturing.

Coiling or clipping?

Increasingly, coiling is the preferred technique, as it is less invasive and so causes fewer complications.

However, there are some circumstances when clipping surgery may be preferred and the doctors looking after you will recommend the most appropriate technique.

Preventing a subarachnoid haemorrhage

While not all the risk factors for a subarachnoid haemorrhage can be prevented, the two leading risk factors can.

These are:

  • smoking
  • high blood pressure


Smoking is a major risk factor for a subarachnoid haemorrhage because it raises your blood pressure. There may also be harmful substances in tobacco smoke that could damage the walls of the arteries which could make it more likely that the aneurysm ruptures (bursts open).

If you're committed to giving up smoking but don't want to be referred to a stop-smoking service, your doctor should be able to prescribe medical treatments to help with any withdrawal symptoms that you may have after quitting.

See Treatment for quitting smoking.

High blood pressure

High blood pressure can often be reduced by eating a healthy diet, moderating your alcohol intake, maintaining a healthy weight and doing regular exercise.


Cut down on the amount of salt in your food and eat plenty of fruit and vegetables.

Salt raises your blood pressure. The more salt you eat, the higher your blood pressure. Aim to eat less than 6g (0.2oz) of salt a day – about a teaspoonful.

Eating a low-fat diet that includes lots of fibre (for example, wholegrain rice, bread and pasta) and plenty of fruit and vegetables has been proven to help lower blood pressure. Fruit and vegetables are full of vitamins, minerals and fibre to keep your body in good condition. You should aim to eat five 80g portions of fruit and vegetables every day.


Regularly drinking alcohol above the levels recommended will raise your blood pressure over time. Staying within the recommended levels is the best way to reduce your risk of developing high blood pressure.

Alcohol is also high in calories, which will make you gain weight. This will also increase your blood pressure.


Being overweight forces your heart to work harder to pump blood around your body, which can raise your blood pressure.

If you need to shed some weight, it's worth remembering that losing just a few pounds will make a big difference to your blood pressure and overall health.


Being active and taking regular exercise lowers blood pressure by keeping your heart and blood vessels in good condition. Regular exercise can also help you lose weight, which will also help lower your blood pressure.

Adults should do at least 150 minutes (two hours and 30 minutes) of moderate-intensity aerobic activity (i.e. cycling or fast walking) every week. For it to count, the activity should make you feel warm and slightly out of breath. Someone who is overweight may only have to walk up a slope to get this feeling.

Physical activity can include anything from sport to walking and gardening.

Read more about

preventing high blood pressure

Recovery from a subarachnoid haemorrhage

The amount of time it will take you to recover from a subarachnoid haemorrhage will depend on the severity of the haemorrhage.

The location of the haemorrhage will also affect whether you have any associated neurological conditions, such as loss of feeling in your arms or legs, or problems understanding speech.

Recovery can be a frustrating process. You may make a lot of progress and then suffer setbacks and it is likely you will have good days and bad days.

Feelings of anger, resentment and sadness are common. Talking to other people with similar conditions via support groups can help provide advice and reassurance. An assessment from a clinical psychologist can also be helpful.

The common after-effects of a subarachnoid haemorrhage are outlined below.

Extreme tiredness

During the first three months after your haemorrhage it is normal to feel extremely tired.

Even simple tasks, such as going to the shops, can leave you feeling exhausted. Taking regular short breaks of about half-an-hour in a relaxing environment will help.


After having a subarachnoid haemorrhage, many people find they have

(problems getting to sleep) or they can only sleep for short periods.

Having a set daily routine, where you try to get up and go to bed at the same time every day, can help.

Also, set time aside for relaxation breaks. If you have returned to work, you could talk to your employer about having extra time for breaks.


are common after a haemorrhage but they tend to ease in time. They are not normally as severe as when you had your haemorrhage and you should be able to control them with over-the-counter painkillers such as paracetamol.

Drinking plenty of fluids (two to three litres of water a day) should also help reduce the severity and frequency of headaches.

Unusual sensations

After having a subarachnoid haemorrhage, some people have reported experiencing strange or unusual sensations in their brain. These sensations can be difficult to describe but some people have said that they feel ticklish or like somebody is pouring water across their brain.

Nobody is really sure exactly why these strange sensations occur, but they are common and you should not be concerned about them as they should pass in time.

Loss of feeling or movement

Following a subarachnoid haemorrhage, some people experience a loss of movement and feeling in their arms or legs. This can range from a slight weakness to a complete loss of power.

You may also have problems distinguishing between hot and cold, so you should be careful when taking a bath or showering. A training and exercise plan carried out under the supervision of a physiotherapist can often help restore feeling and movement to affected limbs.

Changes in senses

Many people experience changes to their sense of smell and taste after they have had a subarachnoid haemorrhage. The senses can be heightened or reduced.

You may find that your favourite food now tastes disgusting, while something you hated now tastes delicious. However, these changes in the senses are normally temporary and will resolve as the swelling on your brain goes down.


Following a brain injury, problems with your vision such as blurring, blind spots, black spots and double vision are common.

Your vision will be tested before you leave hospital and if necessary, you will be referred to an ophthalmologist (a doctor who specialises in the care of the eye). Improvement in your vision will usually happen gradually over a number of months.

Caring for others

If you are caring for someone recovering from a subarachnoid haemorrhage you may find it a challenging prospect. They can often have complex needs and engage in challenging and sometimes upsetting behaviour.

Complications of a subarachnoid haemorrhage


A potentially serious early complication of a subarachnoid haemorrhage is that the aneurysm bursts again; this is known as rebleeding.

The risk of rebleeding is highest in the few days after the first haemorrhage and rebleeding carries a high risk of causing permanent disability or death. It is because of this risk that surgery is recommended to take place to repair the aneurysm as soon as possible.

Secondary cerebral ischaemia

Secondary cerebral ischaemia (SCI), sometimes also called delayed ischaemic deficit or vasospasm, is another serious and common complication of a subarachnoid haemorrhage. SCI is when the supply of blood becomes dangerously reduced, disrupting the normal functions of the brain and leading to brain damage.

The cause of SCI is uncertain, but vasospasm of the arteries inside the brain may contribute to it, and it is most common a few days after the initial haemorrhage. Vasospasm is when a blood vessel goes into a spasm, causing the vessel to become narrowed.

Common symptoms are increasing drowsiness progressing to

, with or without other
stroke like symptoms
such as weakness down one side of the body.

There are a number of treatments that can be used to prevent and treat SCI such as a medication called nimodipine. See

treating subarachnoid haemorrhage
for more information about nimodipine.


is a build-up of fluid on the brain. The excess fluid puts pressure on the brain, which can cause it to be damaged.

The damage to the brain can result in a wide range of symptoms, including:

  • headache
  • being sick
  • blurred vision
  • difficulty walking

Hydrocephalus is common after subarachnoid haemorrhage although not all people will have symptoms

The brain is supported by a clear colourless fluid, known as cerebrospinal fluid (CSF). A constant supply of new CSF is produced inside the brain while the old fluid is drained away into blood vessels.

But the damage caused by a subarachnoid haemorrhage can sometimes disrupt this draining process leading to excess CSF inside the brain causing hydrocephalus.

Hydrocephalus may be treated with lumbar punctures, or a shunt. A shunt is a tube that is surgically implanted into the brain and used to drain away the excess fluid.

Read more about the

treatment of hydrocephalus

Long-term complications

There are a number of long-term complications that can affect people after experiencing a subarachnoid haemorrhage. These are outlined below.


Around 1 in 20 of people who have had a subarachnoid haemorrhage develop epilepsy.

Epilepsy is a condition where the normal working of the brain is interrupted, causing a person to have repeated fits or seizures.

There are different types of seizure and symptoms can vary. You may lose consciousness, have muscle contractions (your arms and legs may twitch and jerk) or your body may shake or become stiff. Seizures usually last between a few seconds and several minutes. Brain activity then returns to normal.

In most cases of epilepsy following a subarachnoid haemorrhage, the first seizure occurs within the first year after the haemorrhage.

Epilepsy can be treated using anti-epileptic medicines, such as phenytoin or carbamazepine.

A neurologist will help decide which treatment you may need, and how long you need to take it for.

Cognitive dysfunctions

A cognitive dysfunction is when a person experiences difficulties with one or more functions of their mind, such as memory.

Cognitive dysfunctions are a very common complication of a subarachnoid haemorrhage. It is estimated that 95% of people will have at least one cognitive dysfunction.

Cognitive dysfunctions can take a number of forms, such as:

  • problems with memory – memories before the haemorrhage are normally not affected, but you may have problems remembering new information or facts
  • problems with tasks that require some degree of planning – you may find that even simple tasks, such as making a cup of tea, are difficult and frustrating
  • problems with concentration or attention

There are a number of self-care techniques that you can use to compensate for any dysfunction.

Try breaking tasks down into smaller steps, and using memory aids such as notes or a diary.


occupational therapist
can help with advice on day to day activities while a speech and language therapist can help with communication skills.

The doctor in charge of your care should be able to provide advice on how to access these types of service.

Most people will find that most cognitive functions will improve with time, though problems with memory can be persistent. One study found that around half of people still had ongoing problems with memory a year after their haemorrhage occurred.

Mood disorders

Mood disorders are another common long-term complication of a subarachnoid haemorrhage.

These disorders can take a number of forms, such as:

  • depression
    – feeling very down, hopeless and not getting any real enjoyment out of life
  • anxiety disorder – a constant sense of anxiety and dread that something terrible is going to happen
  • post-traumatic stress disorder
    – where a person often relives a previous traumatic event (in this case the haemorrhage) through nightmares and flashbacks, and they may experience feelings of isolation, irritability and guilt

These mood disorders can be treated using a combination of medication, such as

and talking therapies, such as
cognitive behavioural therapy

Read more about the treatment of depression, anxiety disorder and

post-traumatic stress disorder

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.