A subdural haematoma is a serious brain condition that is caused when blood collects between the skull and the surface of the brain. The blood puts the brain under pressure, which can trigger a wide range of symptoms including:
- vomiting (being sick)
- mental confusion
See subdural haematoma - symptoms for more information
A subdural haematoma occurs when a blood vessel in the space between the skull and the brain (the subdural space) is ruptured. Blood escapes from the ruptured blood vessel, leading to the formation of a blood clot (haematoma), which places pressure on the brain and may cause brain damage.
See subdural haematoma - causes for more information
Types of subdural haematoma
There are two main types of subdural haematoma:
- The haematoma forms immediately after the initial injury (acute subdural haematoma).
- The haematoma forms over a period of two to three weeks after the initial injury (chronic subdural haematoma).
The two types are discussed in more detail below.
Acute subdural haematoma
Acute subdural haematomas are the most serious type of subdural haematoma. They usually occur after severe, high-impact head injuries, often caused motor vehicle accidents, falls and physical assaults.
An acute subdural haematoma is a medical emergency that requires immediate admission to a hospital.
Surgery is usually required to remove the haematoma.
Chronic subdural haematoma
Chronic subdural haematomas are more commonly seen in older people. It is thought that they occur because the natural aging process makes the brain more vulnerable to injury in some people.
This means that even a minor injury can cause bleeding inside the subdural space (in around half of all cases, the injury is so minor that the person cannot remember it).
The symptoms of a chronic subdural haematoma often develop weeks, rather than days, after the initial injury because our brain usually shrinks as we get older, creating more subdural space for the haematoma to expand before it causes any noticeable symptoms.
Chronic subdural haematomas may also be regarded as a medical emergency. Surgery is usually required.
See subdural haematoma - treatment for more information.
Acute subdural haematoma carries a high risk of death. Age is an important factor that affects a person's outlook. For example, people who are:
- under 40 years old have a 20% risk of dying
- 40 to 80 years old have a 65% risk of dying
- 80 years old or over have a 88% risk of dying
People who survive an acute subdural haematoma usually take a long time to recover from the effects of the haematoma. The recovery time will depend on the severity of the haematoma. There can also sometimes be permanent physical and mental disablities.
The outlook for chronic subdural haematoma is much better than the outlook for acute subdural haematoma. However, the condition still carries a moderately high risk of death. An estimated 1 in 20 people will die within the first 30 days after having surgery to treat a chronic subdural haematoma.
See subdural haematoma - recovery for more information
- 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.
- The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.
- Drowsiness is when someone feels extremely tired and uncontrollably near to sleep.
- Haematoma is a collection of blood in the tissues from a leaking blood vessel, which causes bruising.
- To haemorrhage means to bleed or lose blood.
Symptoms of subdural haematoma
The symptoms of an acute subdural haematoma usually develop rapidly after a severe head injury - for example, as the result of a fall, violent assault or motor vehicle accident.
The symptoms of a chronic subdural haematoma often develop within two to three weeks of having a head injury, which is usually minor, such as a light knock to the head.
Symptoms of a subdural haematoma include:
- nausea (feeling sick)
- personality changes - such as being unusually aggressive or having rapid mood changes
- decreased levels of consciousness - such as finding it difficult to keep the eyes open
- speech problems - e.g. slurring words or difficulty saying words
- impaired vision or double vision
- paralysis (lack of movement) on one side of the body
- loss of consciousness
When to seek emergency medical treatment
Always seek emergency medical treatment after a significant head injury. You should go immediately to the accident and emergency (A&E) department of your nearest hospital, or dial 999 to request an ambulance.
A number of risk factors make a person more vulnerable to a less severe head injury resulting in a chronic subdural haematoma.
- being 65 years old or over
- having a previous history of brain surgery
- having a condition that makes you bleed more easily, such as haemophilia, or having a condition that makes your blood more prone to clotting, such as thrombophilia
- taking anticoagulant (blood-thinning) medication to prevent blood clots, such as warfarin or aspirin
Symptoms that could suggest that people in these groups may have developed a subdural haematoma include:
- previous loss of consciousness (passing out)
- not remembering events that occur before or after the injury
- persistent headaches
- persistent vomiting
- changes in behaviour, such as irritability, being easily distracted or having no interest in the outside world
If you or someone in your care has any of the above signs, symptoms or risk factors, you or they should go to the nearest hospital's accident and emergency (A&E) department to seek immediate medical attention.
Causes of subdural haematoma
A subdural haematoma occurs when a blood vessel in the space between the skull and the brain (the subdural space) is ruptured (torn). Blood escapes from the ruptured blood vessel, leading to the formation of a blood clot (haematoma), which places pressure on the brain and may cause brain damage.
Inside the skull, the brain is covered by three protective layers, which are known collectively as the meninges. These are:
- the outer layer that lies next to the skull (the dura mater)
- the middle layer (the arachnoid)
- the inner layer that is closest to the brain (the pia mater)
The space between the two outer membranes (the dura mater and the arachnoid) is called the subdural space.
A subdural haematoma occurs when a blood vessel in the subdural space is ruptured (torn) usually due to a head injury. This enables blood to escape and form a haematoma (an accumulation of blood that clots to form a solid swelling).
As the bleeding continues, the subdural haematoma will grow, taking up more room inside the skull. The haematoma may press on the brain, leading to a build-up of pressure inside the skull. This is referred to as intracranial pressure (ICP).
As the pressure increases, it is thought to have a harmful effect on the cells of the brain. This causes the brain tissue to swell, leading to a further increase in pressure. The increased pressure squashes the brain against the wall of the skull, resulting in symptoms such as headaches, confusion and muddled speech.
Left untreated, a subdural haematoma may damage your brainstem. The brainstem is the part of the brain that helps to regulate many of the body's vital functions, such as consciousness and breathing. Therefore, brainstem damage can sometimes result in coma (where someone is unconscious for a long period of time) followed by death.
In most cases, subdural haematomas develop after a head injury causes a large amount of blood to escape from a torn blood vessel.
Acute subdural haematomas
It is thought that the most common cause of acute subdural hematoma is the brain being subjected to what is known as an 'acceleration-deceleration force'. This is when the skull and the brain inside the skull are propelled in one direction with great force (acceleration) before coming to a sudden stop (deceleration).
The most common ways that the brain can be subjected to this type of injury are:
- motor vehicle accidents
- violent assaults
These types of injury can damage the brain in three main ways:
- they can cause tearing of the veins that carry blood from the brain to the heart and lungs
- they can damage the arteries that provide the brain with oxygen-rich blood
- they damage the tissue of the brain, resulting in bleeding
As well as the direct damage caused by the pressure of the haematoma on the brain, the damage to the blood vessels inside the brain can disrupt the blood flow to the brain. This can often result in secondary brain damage, which is more severe than the damage caused by the initial injury.
Chronic subdural haematomas
The fact that most people's brains tend to shrink to a certain extent as they grow older is thought to play an important part in the development of a chronic subdural haematoma.
This shrinkage places the veins that carry blood out of the brain under increased tension, much like a rubber band that has stretched to its maximum extent. The increase in tension makes the veins much more vulnerable to damage, so that even a minor injury can result in the veins tearing.
Unlike acute haematomas, these tears are usually minor, causing low levels of bleeding. However, over the course of several weeks, the amount of blood gradually builds up and a haematoma develops.
A number of factors may increase your risk of developing a chronic subdural haematoma. These include:
- alcohol misuse
- anticoagulant medicines
- having a history of seizures (fits)
- having an implanted device, known as a ventriculoperitoneal (VP) shunt
- certain health conditions that affect the ability of the blood to clot
These risk factors are discussed below.
Over half of all cases of chronic subdural haematoma affect people who are over 60 years old. The chances of developing one increase with age.
This is mainly due to the fact that as a person gets older their brain reduces in size, creating a larger subdural space (more space between the brain and the skull).
Misusing alcohol can shrink the brain over a period of time, which can result in a larger subdural space being created.
Taking anticoagulant (blood-thinning) medicines can increase the risk of developing a subdural haematoma. Anticoagulants are often used to treat or prevent conditions that are caused by the blood clotting too quickly, such as deep vein thrombosis (DVT) and heart attacks.
Anticoagulant medicines, such as warfarin and heparin, work by slowing down the body's blood clotting process. This can prevent a bleed in the subdural space from clotting quickly enough to stop it. As a result, a chronic subdural haematoma can form.
A seizure occurs when the normal electrical activity of the brain is disrupted, which can cause the brain and body to behave strangely, such as losing conciousness or shaking uncontrollably.
Exactly why seizures increase the risk of developing a chronic subdural haematoma is unclear. It may be that the abnormal electrical activity during a seizure makes the brain more vulnerable to damage.
Ventriculoperitoneal (VP) shunt
A ventriculoperitoneal (VP) shunt is a thin tube that is implanted in the brain to drain away any excess fluid to another part of the body. VP shunts are used to treat a condition called hydrocephalus.
Occasionally, a VP shunt can overdrain, which can cause a chronic subdural haematoma.
Certain health conditions
Some health conditions, such as haemophilia and thrombocytopenia prevent the blood from clotting properly, which may mean that you bleed more heavily and for longer than usual.
Diagnosing subdural haematoma
Subdural haematomas are diagnosed based on a person's medical history, symptoms and the results of an imaging scan of the brain.
Acute subdural haematomas
Due to the nature of the condition, most cases of acute subdural haematomas are diagnosed in an accident and emergency (A&E) department.
After a head injury, healthcare professionals use the Glasgow Coma Scale (GCS) to assess how severely your brain has been damaged. The GCS scores you on:
- your verbal responses (whether you can speak appropriately or make any sounds at all)
- your physical response (whether you can move voluntarily or in response to stimulation)
- how easily you can open your eyes
A slightly different version of the GCS is used for children under five years old.
If you achieve a score of 15 (the highest possible score) it indicates that you know who and where you are, that you can speak and move as instructed, and that your eyes are open.
A score of 3 (the lowest possible score) means that you cannot open your eyes and you cannot move or make a noise. This score indicates that your body is in a deep coma (a sleep-like state in which you are unconscious for a long time).
Depending on your score, head injuries are classed as:
- minor - a GCS score of 14 to 15
- moderate - a GCS a score of 9 to 13
- severe - a GCS score of 3 to 8
A GCS score of 8 or below is commonly seen in people with an acute subdural haematoma. As a precaution, anyone with a GCS score below 15 should be given a computerised tomography (CT) scan within one hour of the request being made by A&E staff.
A CT scan is where a series of X-rays of the inside of your body are taken and a computer then assembles the images. The resulting image forms a cross-section of the part of the body that was scanned.
If you have an acute subdural haematoma, it usually shows up on a CT scan as a white semi-circular mass, just under the surface of your skull.
Chronic subdural haematoma
Diagnosing cases of chronic subdural haematoma can be more difficult for two reasons:
- many of the symptoms of a chronic subdural haematoma are shared by other health conditions, such as dementia, Parkinson's disease or brain tumour
- many people cannot recall sustaining a head injury that could be associated with the onset of symptoms
It may therefore take several days or possibly weeks before the correct diagnosis is confirmed and you may be referred for a series of tests that are designed to rule out other possible causes of your symptoms.
Most cases of chronic subdural haematoma can be diagnosed using a CT scan because the haematoma will often show up as a mass that is of a different density to the brain. However, in some cases, the blood clot can take on a similar density, which makes it harder to detect.
If this is the case, you may have a magnetic resonance imaging (MRI) scan instead. A MRI scan uses a strong magnetic field to produce detailed images of the inside of the body.
Treating subdural haematoma
Surgery is usually recommended for all but the smallest of subdural haematomas. For very small haematomas, a policy of 'watchful waiting' may be recommended. This is because with careful monitoring, small subdural haematomas may heal without the need for an operation.
Surgery is usually recommended for acute subdural haematomas that are 10mm (0.4 inches) or larger, and for most cases of chronic subdural haematomas.
Two widely used surgical techniques are used to treat a subdural haematoma:
- Craniotomy - a section of your skull is temporarily removed to allow the surgeon access and remove the haematoma
- Burr holes - a small hole is drilled into your skull and a tube is inserted through the hole to help drain the haematoma
These techniques are discussed in more detail below.
A craniotomy is used for acute subdural haematomas and some chronic subdural haematomas. The surgery is carried out by a neurosurgeon (an expert in surgery of the brain and nervous system). A craniotomy usually takes a few hours to complete.
The neurosurgeon temporarily removes a section of the skull. The location of the piece of skull to be removed depends on where subdural haematoma is. The blood clot is gently removed using suction and irrigation (washing away with water). After the procedure, the removed section of skull is replaced and fixed using strong stitches or small mini-plates.
A craniotomy is usually performed under a general anaesthetic, which means that you will be asleep during the surgery.
The most common complication of a craniotomy is that a blood clot develops at the site of the surgery. This occurs in an estimated 1 in 20 cases and will require further surgery to remove the blood clot.
Less common complications of a craniotomy include:
- damage to nerves, which could result in muscle weakness or paralysis (lack of movement)
- loss of some mental functions, such as memory loss
If the surgery goes well and you do not have any complications, you may be well enough to leave hospital after a few days. If you have complications, it may be several weeks before you are well enough to leave hospital.
Burr holes are usually the preferred treatment option for most chronic subdural haematoma cases. The process involves making tiny holes in the skull to allow the neurosurgeon to drain the blood from the subdural haematoma. The haematoma is drained through a flexible rubber tube fed through the burr holes.
Burr hole surgery is sometimes carried out under local anaesthetic, which means that the area is numbed, so you will not feel any pain, although you will be awake during the procedure.
Small tubes may be temporally left inside the burr holes for a few days to help drain away any blood and debris from the site of the surgery. Research results published in 2009 reported that using drainage tubes reduces the risk of complications.
After the procedure, the burr holes can be closed using either stitches or staples. Most people are well enough to leave hospital within three to nine days.
Complications of burr hole surgery include:
Symptoms that occurred before surgery may persist after surgery - for example:
- hemiparesis - muscle weakness on one side of the body
- dysphasia - problems with certain brain functions that affect talking and understanding others
Recurrence of the haematoma occurs in an estimated 1 in 10 cases and may require further surgery to correct.
Recovering from subdural haematoma
In some cases, a subdural haematoma can cause damage to the brain that requires more time and care to recover from.
If this is the case, you may need further treatment from a neuro-rehabilitation team. This team may include physiotherapists, speech therapists and occupational therapists who will help you to regain your ability to move, speak and live independently.
It can take a year or more to recover from a severe subdural haematoma. It is also important to remember that there may be some permanent damage, such as changes to your moods and concentration, or memory problems and weakness in your limbs.
Getting back to normal
Recovery after having a subdural haematoma will vary depending on how severe it is. For example, one person may make a good recovery while another may have a moderate disability. It is also possible for someone to have a severe disability or to be in a vegetative state (function unconsciously). In very severe cases, death is also a possibility.
After being discharged from hospital, it may take some time before you begin to feel normal again.
The length of time that it takes to completely recover from a subdural haematoma will vary from person to person.
You may feel ready to return to work a few weeks after leaving hospital. But before you do, you may have to meet with your medical team at your outpatient's appointment. This may be some time after you are discharged.
While you are recovering, it is important to take things easy and not to do too much too soon. Make time every day to completely rest your brain from any kind of distraction, such as the radio or television.
People who have a serious brain injury, such as a subdural haematoma, are not allowed to drive. They have a legal obligation to inform the Driver and Vehicle Licensing Agency (DVLA) and their insurance company about the injury.
It is likely that the DVLA will withdraw your licence for six months or a year. After that time you can reapply for your licence, depending on your recovery.
If you have a seizure during your recovery from surgery, you will have to spend a year without having any further seizures before you will be allowed to drive a car or a motorcycle. It will take longer before you are allowed to drive a heavy goods vehicle.
More information about the medical rules for driving is available on the Directgov website.