What is a subdural hematoma?

A subdural hematoma is a buildup of blood on the surface of the brain. The blood builds up in a space between the protective layers that surround your brain.

Your brain sits within a bony skull. Inside your skull and over the brain there are 3 layers called the meninges. These layers cover and protect the brain. The outermost covering is just inside the skull. It’s a tough, fibrous layer called the dura mater, or usually just dura. On the inside of the dura is a layer called the arachnoid. Closest to the brain is a membrane called the pia. Cerebrospinal fluid (CSF) fills the space inside the meninges. CSF also helps cushion your brain.

The dura lines the skull and surrounds the brain. In a subdural hematoma, the blood seeps between the dura and the arachnoid layers. It collects inside the brain’s tough outer lining. This bleeding often comes from a blood vessel that breaks within the space around the brain. This most often happens because of a head injury. The injury can be mild. The blood may press against the brain and damage the tissue. A subdural hematoma can be life-threatening.

A subdural hematoma is not uncommon. It happens in some people who get a severe head injury. Younger men are most likely to get these types of injuries. Older adults are at higher risk for a subdural hematoma, even with a mild head injury. This is because the veins surrounding the brain are more likely to tear. About a third of subdural hematomas happen in older adults. In babies, subdural hematomas are often from shaken baby syndrome.

What causes a subdural hematoma?

The most common cause for a subdural hematoma is head injury. This can be from a car crash, fall, or violent attack. This sudden impact can strain the blood vessels within the dura, causing them to rip and bleed. Sometimes small arteries also break within the subdural space. In some people, the brain shrinks (often from aging), and the subdural space gets bigger. This can make the blood vessels more likely to break. In people 50 and older, subdural hematomas can be present for days or weeks. These are called chronic subdural hematoma because the blood clot changes into liquid. It becomes dark in color.

Possible causes for a subdural hematoma include:

• Head injury, such as from accidents or violence. This is most common in younger people.
• Brain shrinking (atrophy). This is more common in older adults.
• Medicines to prevent blood clots, such as warfarin, aspirin, and other blood thinners
• Leak of cerebrospinal fluid

Who is at risk for a subdural hematoma?

A subdural hematoma is most often the result of head injury. So people at risk of car crashes or falls are most at risk for this problem. You may have a higher risk for subdural hematoma from:

• Head injury, such as from car crashes, falls, or sudden changes in speed
• Playing high-impact sports
• Advanced age. This makes it more likely that the brain has shrunk, putting the blood vessels at risk for damage.
• Alcohol abuse
• Previous brain injury
• Using blood-thinning medicine
• Violence, such as shaken baby syndrome
• Cerebrospinal fluid leak (rare)
• Blood vessel rupture at a weak or bulging spot (cerebral aneurysm) (rare)
• Tumor (rare)
• Bleeding disorders such as hemophilia (rare)

What are the symptoms of a subdural hematoma?

A subdural hematoma may cause symptoms right away (acute), or it may slowly grow and cause symptoms at a later time. You may notice the symptoms weeks after an injury or blood vessel breaking (chronic).

Symptoms of a subdural hematoma may include:

• Balance or walking problems
• Confusion
• Dizziness
• Headache
• Nausea or vomiting
• Passing out (losing consciousness)
• Seizures
• Sleepiness
• Speech problems
• Vision problems
• Weakness or numbness that may come and go

How is a subdural hematoma diagnosed?

An acute subdural hematoma is an emergency. You will need a physical exam, including a check of your reflexes, plus your head, eyes, and neck. Doctors usually check for any weakness or signs of brain problems. You may be asked when you first noticed the symptoms. Your doctor may ask you to do some simple things, such as touching your finger to your nose.

Doctors generally do a CT scan or a MRI of your head to look for signs of bleeding. It is very important to find the site of the bleeding. You may need to have one or more tests, such as:

• Blood tests to look for bleeding disorders and measure clotting function
• Blood tests to look for other possible causes of your symptoms
• More imaging of your blood vessels (CT angiography) to find underlying problems

Diagnosis of subdural hematomas often occurs in emergency rooms.

How is a subdural hematoma treated?

Doctors often treat subdural hematomas with surgery to ease pressure on the brain. Your doctor may use a variety of surgeries to treat the hematoma. These include:

• Cutting a flap of skull open to remove the blood (craniotomy)
• Drilling a hole in the skull to allow the blood to drain (burr hole)

If your subdural hematoma is small, doctors might watch it closely instead of doing surgery right away. In this case, you will likely stay in an intensive care unit. You may need:

• A sensor inside your head to measure your intracranial pressure
• Medicines to control symptoms
• Repeated CT scans to watch the hematoma
• A stop to blood-thinning medicines such as warfarin if you normally take them
• Vitamin K therapy. This can reverse the effects of some blood-thinning medicines.

Can a subdural hematoma be prevented?

Protecting yourself from head injuries may help prevent subdural hematomas. It is important to wear a helmet when riding a motorcycle, scooter, bicycle, or skateboard. Wearing seatbelts when in a car and using safety equipment in dangerous situations may help protect your head from injury. You can take steps to prevent falls.

When should I call my healthcare provider?

A subdural hematoma is an emergency. If you or someone else has had a head injury and has the symptoms listed above, you should call 911  or go to the nearest emergency room.

Key points about subdural hematomas

• A subdural hematoma is a collection of blood that forms on the surface of the brain. The blood may press against the brain and damage the tissue. A subdural hematoma can be life-threatening.
• A chronic subdural hematoma may happen in older people after a minor head injury.
• A subdural hematoma may happen after a severe head injury.
• Doctors often treat subdural hematomas with surgery to ease pressure on the brain.
• If you have a subdural hematoma, you need emergency treatment.
• Symptoms may happen right away or develop over weeks.