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 is often 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 with 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 1/3 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. People age 50 and older may have subdural hematomas for days or weeks. These are called chronic subdural hematomas because the blood clot changes into liquid. It becomes a dark 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 for 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'll need a physical exam. This exam will include a check of your reflexes, plus your head, eyes, and neck. Healthcare providers usually check for any weakness or signs of brain problems. You may be asked when you first noticed the symptoms. Your provider may ask you to do some simple things, such as touching your finger to your nose.

Healthcare providers generally do a CT scan or an MRI of your head to look for signs of bleeding. It's very important to find the site of the bleeding. You may need to have 1 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

Subdural hematomas are often diagnosed in emergency rooms.

How is a subdural hematoma treated?

Healthcare providers often treat subdural hematomas with surgery to ease pressure on the brain. Your provider 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, healthcare providers might watch it closely instead of doing surgery right away. In this case, you'll likely stay in an Intensive Care Unit. You may need:

• A sensor inside your head to measure your intracranial pressure

• Medicines to control symptoms

• CT scans to watch the hematoma

• To stop taking blood-thinning medicines, such as warfarin, if you normally take them

• Vitamin K therapy, which can reverse the effects of some blood-thinning medicines

Can a subdural hematoma be prevented?

Protect yourself from head injuries to help prevent subdural hematomas. It's 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 911or go to the nearest emergency room.

Key points about subdural hematomas

• A subdural hematoma is blood that collects 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.

• Healthcare providers 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.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions. They can also help you remember what your healthcare provider tells you.

• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your healthcare provider gives you.

• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is advised and what the results could mean.

• Know what to expect if you do not take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your healthcare provider if you have questions.