What is an acute subdural haematoma?
An acute subdural haematoma (aSDH) is a collection of clotting blood that fills up the space between the outer covering of the brain (dura) and the brain itself. The bleeding happens when veins on the surface of the brain tear after a head injury. The blood keeps accumulating and pushing on the brain, causing severe disability and often death if left untreated.
Key symptoms and signs
These depend very much on how extensive the bleeding is and how traumatic the injury is. Some patients with aSDH may be unconscious right from the initial injury, while others may still be conscious and can be assessed by the healthcare team.
If you are unconscious, the doctors will determine how extensive the damage is by checking the following:
- Response to pain – this is usually part of the Glasgow Coma Scale (GCS) assessment to determine the patient’s level of consciousness
- Response of pupil to light – an unreactive or dilated pupil is often worrying as it suggests a build-up of pressure in the skull or damage to brain tissue.
If a patient is conscious, signs & symptoms that we look for include:
- Bruise or wound – this may be found on your head, at the site where you have sustained trauma; bruising behind your ear may indicate a fracture along the base of your skull
- Change in mental status – an aSDH can cause a person to become disorientated and drowsy; this is usually picked up by friends and family members
- Headache – worse when lying down or straining
- Nausea and vomiting – you may feel the need to be sick or will vomit, especially in the morning
- Blurred or double vision – any sudden change in vision is a sign to seek medical help
- Weakness or clumsiness – this could mean that there is a growing collection of blood or injury to the brain
- Clear fluids or blood coming out from your nose or ears – this is an indication of a fracture along the base of your skull
Major Risk Factors (Who is affected?)
Head injury is the most common cause of aSDH but there are a few risk factors that put someone at a higher risk of developing an aSDH. These include:
- Cerebral atrophy – this refers to an overall decrease in brain volume and can be due to old age, chronic alcohol use and even having a previous traumatic brain injury.
- Antithrombotic and anticoagulation therapy (aka blood thinners) – this refers to medications such as aspirin, clopidogrel, and warfarin. It has been shown that being on anticoagulation therapy increases the risk of aSDH 7-fold in males and 26-fold in females.
aSDHs are usually diagnosed via a brain scan (most likely a CT scan) which allows for doctors to visualise the collection of blood located in the subdural space. Doctors look for the presence of a crescent-shaped collection of blood along the outside of the brain. A hyperdensity has an appearance brighter than the surrounding brain tissue, and in this case is a sign of fresh blood.
Doctors also look for the presence of something called midline shift, which will not only inform them that the pressure in the skull is elevated but also how badly injured the underlying brain tissue is. The extent of the midline shift will also play a role in determining how urgently the patient requires surgery.
The doctors will first stabilise the patient by ensuring that there is an adequate supply of oxygen getting to the patient and that the blood pressure is under control. After stabilising the patient and confirming the presence of an aSDH, the doctors will decide if the patient is best suited to conservative or surgical management.
This can be considered if the aSDH is small in a clinically stable patient or if the patient is unfit for surgery. Conservative treatment may include:
- Follow-up brain scans
- Administration of medications to help with clotting (i.e. platelets and clotting factors)
- Administration of anti-seizure medications
However, patients who have clots that are becoming larger or worsen clinically will require surgery.
The general principles of surgery for aSDH are:
- Drain the clotting blood
- Relieve pressure on the brain
To drain the clotting blood, the patient will be placed under general anaesthesia and the surgeon will remove a piece of skull to gain access to this clot. The piece of skull removed is known as a bone flap. At the same time, this act relieves the pressure that has been built up within the closed space of the skull. This helps reduce the chance of brain tissue being forced out of the skull (a phenomenon known as tonsillar herniation), which can ultimately lead to death.
In this context, decompression refers to the act of relieving the pressure built up within the skull. If the bone flap is put back in place, the procedure is known as a decompressive craniotomy. We’ve created a medically illustrated video of the procedure that includes real footage of surgery if you want to know more.
If the bone flap is left out, the procedure is known as a decompressive craniectomy. As there is no common consensus on which procedure is better for patients, a study known as the Rescue-ASDH trial is being conducted to determine this.
You can check out Mr. Chris Uff from The Royal London Hospital explain more about this trial here:
Complications can arise due to the raised pressure within the skull or due to direct injury to brain from the traumatic accident.
Patients who experience an aSDH may suffer from complications such as permanent weakness or loss of sensation. This depends on which part of the brain has been injured. Seizures, infections or even recurrent clot formation during recovery are also some complications that may occur.
In severe cases, some patients may enter a coma or even face death. Unfortunately, the overall mortality rate ranges from around 50-90%.
Long Term Picture
Many people with small aSDHs can make a quick and full recovery. If there is no damage to the underlying brain tissue, 4 out of 5 people with aSDH survive. If there is an injury to the underlying brain tissue patients can be left with long-term problems even after treatment. These problems include:
- Weakness in your limbs
- Problems with speaking or swallowing
- Alterations in mood, concentration or memory
Fortunately, we have healthcare professionals who are able to help you with your rehabilitation. They include physiotherapists, speech therapists, occupational therapists and even psychologists.
What can I do to prevent myself developing an ASDH?
Unfortunately, accidents that are out of our control may occur and the best way we can lower our risk of getting an aSDH would be to change our lifestyles. Some good changes we can adopt include drinking less alcohol and exercising regularly. Wearing protective gear such as helmets while participating in certain physical activity (e.g. cycling, rollerblading, etc.) can be useful too.
For the elderly, measures that can be taken especially if you are on anticoagulants include reducing the risk of falls by decluttering your home, placing anti-slip mats in the bathrooms or even have handrails installed at home.
For patients on certain blood thinners (e.g. warfarin), it is important to go for your regular blood tests to check that the thickness of your blood is within the intended range. Discussing with your physician on whether the dosage of your blood thinners are appropriate is also a valid measure in avoiding over-anticoagulation.
Key takeaway messages
- An acute subdural haematoma (aSDH) refers to a collection of clotting blood found in the subdural space
- Risk factors include old age, chronic alcohol use, and use of blood thinners
- aSDHs are dangerous and will require the evaluation of a specialist
- Diagnosis and the need for surgery will be made based on the CT scan findings
- Treatment include conservative measures in stable patients and surgery in severe cases.
You can check out our Youtube video on aSDH at this link for actual surgical footage: https://tinyurl.com/brainbookaSDH