A subdural hematoma occurs when blood collects on your brain’s surface beneath the skull. Subdural hematomas can be life-threatening. They usually result from a head injury.

Subdural hematomas are either acute or chronic. Acute subdural hematomas commonly form because of a severe head injury. Approximately 20 to 30 percent of people regain full or partial brain function after having an acute subdural hematoma.

Chronic subdural hematomas develop due to a minor head injury.

A blood clot on the surface of the brain is also called a subdural hematoma.

A subdural hematoma occurs when a vein ruptures between your skull and your brain’s surface.

Acute subdural hematomas

If you sustain a major brain injury, this area can fill with blood and cause life-threatening symptoms. This is called an acute subdural hematoma. It’s the most dangerous type of subdural hematoma.

Acute subdural hematomas are usually caused by:

  • a car accident
  • a blow to the head
  • falling

Acute subdural hematomas form quickly, and the symptoms appear immediately. About 50 to 90 percent of people who develop acute subdural hematomas die from the condition or its complications.

Chronic subdural hematomas

Chronic subdural hematomas are usually caused by mild or repeated head injuries. These are common in older adults who repeatedly fall and hit their heads. Some chronic subdural hematomas occur with no apparent cause.

The higher rate of this condition in older adults may also be because the brain shrinks as people age. This causes extra space in the skull, allowing the veins to be more easily damaged during a head injury. Symptoms of chronic subdural hematomas aren’t noticeable immediately and may not appear for several weeks.

Chronic subdural hematomas are easier to treat than acute subdural hematomas. However, they can still cause life-threatening complications.

Acute subdural hematomas cause symptoms right away. However, people with chronic subdural hematomas may have no symptoms at all.

Common symptoms of a subdural hematoma are:

  • slurred speech
  • loss of consciousness or coma
  • seizures
  • numbness
  • severe headaches
  • weakness
  • visual problems

You should go to the doctor right away if you have any of these symptoms. These symptoms are also signs of other very serious health conditions. Symptoms of chronic subdural hematoma can be similar to the symptoms of dementia, stroke, tumors, or other problems in the brain.

A subdural hematoma can be diagnosed using imaging tests, such as a CT or MRI scan. These scans provide your doctor with an in-depth look at your:

  • brain
  • skull
  • veins
  • other blood vessels

These scans can also reveal if there’s any blood on your brain.

Your doctor may also order a blood test to check your complete blood count. A complete blood count test measures your red blood cell count, white blood cell count, and platelet count. A low level of red blood cells can indicate significant blood loss.

Your doctor may also give you a physical examination to check your heart rate and blood pressure for evidence of internal bleeding.

An acute subdural hematoma can only be treated in an operating room.

A surgical procedure called a craniotomy may be used to remove a large subdural hematoma. It’s normally used to treat acute subdural hematomas. In this procedure, your surgeon removes a part of your skull in order to access the clot or hematoma. They then use suction and irrigation to remove it.

For an acute subdural hematoma, a craniotomy may be a necessary life-saving procedure. But it still has risks. In one study, 18 percent of patients died within 30 days of the surgery.

A burr hole can be used to drain chronic subdural hematomas as well as acute ones that are smaller than one centimeter at the thickest point. First, your surgeon creates small holes in your skull and then places rubber tubes in them. The blood from the hematoma drains out through these holes. Though recovery rates vary, 80 to 90 percent of patients experience significant brain function improvement after this procedure.

Your doctor may prescribe anti-seizure medications to treat or prevent seizures that might be caused by the subdural hematoma. Medication may also be used to treat your brain injury. Corticosteroids are often prescribed to reduce inflammation in the brain.

Complications of subdural hematomas may occur soon after the injury or sometime after the injury has been treated.

These complications may include:

  • brain herniation, which puts pressure on your brain and can cause a coma or death
  • seizures
  • permanent muscle weakness or numbness

The extent of complications depends on the severity of your brain injury. Other health issues may affect either chronic or acute subdurals. People who take anticoagulants (blood thinners) are at higher risk. People over the age of 65 also have a higher risk, especially for the chronic type.

Seizures can still occur even after you recover from a subdural hematoma and it has been removed.

Your outlook for recovery depends on the type of brain injury you have and where it’s located. Your doctor will create a treatment and recovery plan that’s best for you.