Disorders

What is traumatic brain injury?

Reviewed June 2026 by Michael S. Jaffee, MD, FAAN

Definition: Traumatic brain injury (TBI) is an injury that affects how the brain works. It’s caused by an external force, such as a blow, jolt, or impact to the head or body.

TBI can range from mild (such as a concussion) to severe injuries that require long-term medical care and rehabilitation. TBI is a leading cause of death and disability worldwide, affecting people of all ages. In the United States alone, it has led to about 69,000 deaths and more than 214,000 hospital stays in a single year.

A TBI can be mild, moderate, or severe. These terms don’t refer to how severe your symptoms are. Instead, they’re based on several factors right after you get injured:

  • The Glasgow Coma Scale, which helps doctors measure your level of consciousness
  • Findings from a CT scan
  • How long you’re unconscious (knocked out), if at all
  • How long you have post-traumatic amnesia, which is a state of confusion and memory loss after an injury, if at all

While TBI can happen to anyone, it’s more likely to affect some groups than others. For example, men are about twice as likely to experience a TBI compared to women, and many hospitalizations involve older adults.

A TBI occurs in two stages:

  • Primary injury: This is the damage that happens right away from a fall, accident, or blow to the head.
  • Secondary injury: Minutes to days after a moderate or severe TBI, additional damage can develop due to swelling, reduced blood flow, inflammation, and increased pressure in the brain. This second stage can make the injury worse and is a key focus of treatment.

What are the symptoms of traumatic brain injury?

Symptoms can vary depending on how mild or severe the injury is.

Mild TBI symptoms can include:

  • Headache
  • Feeling dazed or confused
  • Trouble with memory, attention, or concentration
  • Fatigue
  • Changes in mood
  • Changes in sleep

Moderate to severe TBI symptoms can include:

  • Worsening headache
  • Repeated vomiting or nausea
  • Weakness or numbness
  • Difficulty waking up
  • Slurred speech
  • Loss of coordination
  • Increased confusion or agitation

Severe TBI can also lead to long-term changes in thinking, mood, and physical abilities.

What are the causes and risk factors of traumatic brain injury?

TBI happens when the brain is suddenly moved. You don’t need to hit your head to have a TBI. For example, if your body is jolted suddenly in a car crash, your brain might bounce against the inside of your skull.

Common causes of TBI include:

  • Falls
  • Car crashes
  • Blows to the head
  • Sports-related injuries
  • Blast-related injuries
  • Violence, including domestic violence
  • Shaken baby syndrome

These events can also cause bruising, bleeding, or widespread damage to brain cells.

How is traumatic brain injury diagnosed?

Doctors use a combination of exams and imaging tests to diagnose TBI.

  • A neurological exam can assess alertness, movement, and response using tools like the Glasgow Coma Scale.
  • Imaging tests such as CT or MRI scans help identify bleeding, swelling, or other brain injuries.
  • Research continues in areas like advanced imaging, blood tests, brain wave evaluation, and eye tracking.

What treatments are available for traumatic brain injury?

Treatment depends on how severe the injury is, but the main goals are to stabilize the person, prevent further brain damage, and support recovery.

Emergency and early care

  • Maintaining breathing and blood flow
  • Preventing low oxygen levels and low blood pressure
  • Rapid transport to a hospital with specialized care

Hospital and acute treatment

  • Monitoring and controlling pressure inside the brain (intracranial pressure)
  • Medications to reduce brain swelling or prevent seizures
  • Surgery if there’s significant bleeding or pressure

Intensive care (for severe TBI)

  • Close monitoring of brain pressure and blood flow
  • Use of medications or procedures to maintain brain function

Rehabilitation and long-term care
Recovery may take months or years and often includes:

  • Physical therapy, such as specialized balance (vestibular) therapy
  • Occupational therapy, such as specialized vision (oculomotor) therapy
  • Speech and cognitive therapy
  • Emotional and psychological support

Living well with traumatic brain injury

TBI can affect thinking, movement, mood, and daily life. Some people recover fully, while others live with long-term effects. Support from health care providers, rehabilitation specialists, and caregivers plays an important role in helping people live well after a TBI.

Caring for and navigating traumatic brain injury

Explore our resources about living well after a TBI.

Frequently asked questions

Do you have to lose consciousness to have a traumatic brain injury?

No. You can have a TBI even if you don’t lose consciousness. A TBI happens when a blow or jolt affects how the brain works, and it can range from mild to severe.

For example, two out of three concussions (a mild type of TBI) don’t cause unconsciousness.

How long does it take to recover from a traumatic brain injury?

Recovery looks different for everyone and can vary based on severity of injury. Some people feel better within weeks, while others may need months or even years of care and support.

Can a TBI cause long-term or permanent problems?

Yes. Some TBIs can lead to lasting changes in thinking, mood, or physical abilities. While many people improve over time, others may continue to live with ongoing effects.

When should someone seek medical care after a head injury?

It’s important to seek care right away if symptoms feel serious or get worse. Watch for signs like repeated vomiting, trouble waking up, slurred speech, weakness, or increasing confusion. These can be signs of a more serious injury. If you experience any lasting symptoms (such as headaches, dizziness, or difficulties with attention or concentration) after an injury, it’s important to talk to your doctor.