Traumatic brain injury (TBI) is damage to the brain caused by an outside force – a blow, a jolt, a fall or an object that enters the skull. The term covers everything from a mild concussion that heals within weeks to severe injuries with lasting disability. Doctors sort TBI by severity, by the way the injury happened and by the kind of damage found on imaging. Each of these views influences treatment and rehabilitation.
How Common Is Traumatic Brain Injury?
According to the Centers for Disease Control and Prevention (CDC), there were 69,473 TBI-related deaths in the United States in 2021 – about 190 every day. In 2020, about 214,110 people were hospitalized with a TBI. Falls are the leading cause of TBI-related hospitalizations, especially among adults aged 75 and older. Firearm-related suicide is the leading cause of TBI-related deaths. Motor vehicle crashes, assaults and sports injuries are other major causes.
Severity: Mild, Moderate and Severe
Right after the injury, doctors assess consciousness with the Glasgow Coma Scale (GCS). It scores three responses:
- Eye opening – 1 to 4 points (from no response to opening the eyes spontaneously)
- Verbal response – 1 to 5 points (from no sound to clear, oriented speech)
- Motor response – 1 to 6 points (from no movement to following commands)
The total ranges from 3 to 15:
- 13–15: mild TBI – this includes most concussions
- 9–12: moderate TBI
- 3–8: severe TBI – the patient is in a coma
Other factors also count: the length of unconsciousness, the duration of post-traumatic amnesia (the period in which no new memories are formed) and the findings on CT or MRI. A “mild” injury is not always harmless – some people have symptoms for months. Typical warning signs are described in Traumatic Brain Injury Symptoms.
Mechanism: Closed, Penetrating and Blast Injuries
Closed (blunt) injuries
The skull stays intact. The brain is injured because the head strikes an object or is suddenly accelerated and stopped, as in a car crash or a fall. The brain moves inside the skull and hits the bony inner surface; nerve fibers can be stretched and torn. Most TBIs are closed injuries.
Penetrating injuries
An object – most often a bullet, sometimes a knife or a bone fragment – breaks through the skull and the hard outer membrane of the brain (dura). The damage follows the path of the object. Penetrating injuries are less common, but often fatal, and carry a high risk of infection.
Blast injuries
Explosions injure the brain through the pressure wave itself, through flying debris and by throwing the body against objects. Blast-related TBI became a major topic in the military during the wars in Iraq and Afghanistan.
Primary and Secondary Brain Injury
The brain sits inside the rigid skull, which cannot expand. The primary injury happens at the moment of impact: bruising, bleeding and torn nerve fibers. It cannot be undone.
In the following hours and days, a secondary injury can develop. The brain swells, the pressure inside the skull (intracranial pressure) rises and blood flow drops. Low oxygen levels, low blood pressure, high fever and seizures make this worse. Much of acute care in the hospital is aimed at preventing this secondary damage.
Types of Traumatic Brain Injury
Concussion
The most common form. A concussion disrupts brain function without visible damage on standard CT. Loss of consciousness is not required. Typical symptoms are headache, dizziness, confusion, trouble concentrating and sleep problems. Most people recover within days to weeks.
Contusion
A bruise of the brain tissue with small bleeds, often at the front and the underside of the frontal and temporal lobes, where the brain rubs against rough bone. Contusions can grow during the first days.
Coup-contrecoup injury
A contusion at the point of impact (coup) and a second one on the opposite side (contrecoup), because the brain bounces back against the skull.
Diffuse axonal injury
Strong rotational forces, typical in high-speed crashes, tear the long nerve fibers (axons) in many places. Standard CT may look nearly normal, while MRI shows small lesions. Diffuse axonal injury is a frequent cause of prolonged coma and lasting disability.
Epidural hematoma
Bleeding between the skull and the dura, usually from a torn middle meningeal artery after a skull fracture at the temple. Typical is a “lucid interval”: the person is briefly unconscious, then awake and talking – and deteriorates within hours as the bleeding expands. Fast surgery to remove the blood can save lives.
Subdural hematoma
Bleeding between the dura and the brain from torn veins. An acute subdural hematoma follows severe trauma and is often accompanied by other brain damage. A chronic subdural hematoma develops slowly over weeks, mostly in older adults and in people who take blood thinners – sometimes after a minor fall that has long been forgotten. Signs are headache, confusion, a change in personality or weakness on one side.
Traumatic subarachnoid hemorrhage
Bleeding into the space between the brain and the thin inner membranes, where the cerebrospinal fluid circulates. It is very common after TBI and usually shows up on CT.
Intracerebral hemorrhage
Bleeding inside the brain tissue itself, often together with contusions.
Skull fractures
Fractures can be linear, depressed (bone pushed inward) or located at the base of the skull. Signs of a basilar skull fracture include bruising behind the ear or around the eyes and clear fluid leaking from the nose or ear.
Treatment in the Hospital
Emergency care starts with securing breathing, blood pressure and oxygen supply. Then follow:
- CT scan of the head to find bleeding, swelling and fractures quickly
- Surgery to remove large blood clots (craniotomy) or to raise depressed skull fragments
- Intracranial pressure monitoring with a probe in severe TBI
- Lowering the pressure by raising the head of the bed, sedation, controlled ventilation, drainage of cerebrospinal fluid and hyperosmolar therapy with hypertonic saline or mannitol
- Decompressive craniectomy – removing part of the skull bone so the swollen brain has room – when other measures fail
- Seizure prevention in the first week for selected patients
Steroids, once common, are no longer used for TBI. The large international CRASH trial (2004) found higher mortality in patients who received them, and the Brain Trauma Foundation guidelines advise against them.
Rehabilitation After TBI
Most patients with moderate or severe TBI need rehabilitation, often first in an inpatient rehabilitation hospital. The team includes physiatrists (rehabilitation physicians), physical therapists, occupational therapists, speech-language pathologists, neuropsychologists and social workers. Goals are walking and balance, everyday activities, swallowing, speech, memory and attention, as well as the return to school or work. Recovery can continue for months and years. The National Institute on Disability, Independent Living, and Rehabilitation Research funds TBI Model Systems centers, which offer specialized care and conduct research.
Frequently Asked Questions
What does the Glasgow Coma Scale measure?
It scores eye opening, verbal response and motor response. The total from 3 to 15 classifies a TBI as mild (13–15), moderate (9–12) or severe (3–8).
What is the difference between an epidural and a subdural hematoma?
An epidural hematoma is arterial bleeding between the skull and the dura and can worsen within hours. A subdural hematoma is venous bleeding beneath the dura; the chronic form develops over weeks, often in older adults.
Why are older adults on blood thinners at special risk?
Blood thinners make bleeding in the head more likely and larger, even after a minor fall. Older adults who take them should be checked by a doctor after any blow to the head, often with a CT scan.
Is a concussion a traumatic brain injury?
Yes. A concussion is a mild TBI. Most people recover fully, but rest, a gradual return to activity and medical follow-up are important.
