Traumatic brain injury occurs when an external mechanical force causes brain dysfunction.
Traumatic brain injury usually results from a violent blow or jolt to the head or body. An object penetrating the skull, such as a bullet or shattered piece of skull, also can cause traumatic brain injury.
Mild traumatic brain injury may cause temporary dysfunction of brain cells. More serious traumatic brain injury can result in bruising, torn tissues, bleeding and other physical damage to the brain that can result in long-term complications or death.
Traumatic brain injury can have wide-ranging physical and psychological effects. Some signs or symptoms may appear immediately after the traumatic event, while others may appear days or weeks later.
Mild traumatic brain injury
The signs and symptoms of mild traumatic brain injury may include:
- Loss of consciousness for a few seconds to a few minutes
- No loss of consciousness, but a state of being dazed, confused or disoriented
- Nausea or vomiting
- Fatigue or drowsiness
- Difficulty sleeping
- Sleeping more than usual
- Dizziness or loss of balance
- Sensory problems, such as blurred vision, ringing in the ears, a bad taste in the mouth or changes in the ability to smell
- Sensitivity to light or sound
Cognitive or mental symptoms
- Memory or concentration problems
- Mood changes or mood swings
- Feeling depressed or anxious
Moderate to severe traumatic brain injuries
Moderate to severe traumatic brain injuries can include any of the signs and symptoms of mild injury, as well as the following symptoms that may appear within the first hours to days after a head injury:
- Loss of consciousness from several minutes to hours
- Persistent headache or headache that worsens
- Repeated vomiting or nausea
- Convulsions or seizures
- Dilation of one or both pupils of the eyes
- Clear fluids draining from the nose or ears
- Inability to awaken from sleep
- Weakness or numbness in fingers and toes
- Loss of coordination
Cognitive or mental symptoms
- Profound confusion
- Agitation, combativeness or other unusual behavior
- Slurred speech
- Coma and other disorders of consciousness
Infants and young children with brain injuries may lack the communication skills to report headaches, sensory problems, confusion and similar symptoms. In a child with traumatic brain injury, you may observe:
- Change in eating or nursing habits
- Persistent crying and inability to be consoled
- Unusual or easy irritability
- Change in ability to pay attention
- Change in sleep habits
- Sad or depressed mood
- Loss of interest in favorite toys or activities
When to see a doctor
Always see your doctor if you or your child has received a blow to the head or body that concerns you or causes behavioral changes. Seek emergency medical care if there are any signs or symptoms of traumatic brain injury following a recent blow or other traumatic injury to the head.
The terms "mild," "moderate" and "severe" are used to describe the effect of the injury on brain function. A mild injury to the brain is still a serious injury that requires prompt attention and an accurate diagnosis.
Traumatic brain injury is caused by a blow or other traumatic injury to the head or body. The degree of damage can depend on several factors, including the nature of the event and the force of impact.
Injury may include one or more of the following factors:
- Damage to brain cells may be limited to the area directly below the point of impact on the skull.
- A severe blow or jolt can cause multiple points of damage because the brain may move back and forth in the skull.
- A severe rotational or spinning jolt can cause the tearing of cellular structures.
- A blast, as from an explosive device, can cause widespread damage.
- An object penetrating the skull can cause severe, irreparable damage to brain cells, blood vessels and protective tissues around the brain.
- Bleeding in or around the brain, swelling, and blood clots can disrupt the oxygen supply to the brain and cause wider damage.
Common events causing traumatic brain injury include the following:
- Falls. Falling out of bed, slipping in the bath, falling down steps, falling from ladders and related falls are the most common cause of traumatic brain injury overall, particularly in older adults and young children.
- Vehicle-related collisions. Collisions involving cars, motorcycles or bicycles — and pedestrians involved in such accidents — are a common cause of traumatic brain injury.
- Violence. About 20 percent of traumatic brain injuries are caused by violence, such as gunshot wounds, domestic violence or child abuse. Shaken baby syndrome is traumatic brain injury caused by the violent shaking of an infant that damages brain cells.
- Sports injuries. Traumatic brain injuries may be caused by injuries from a number of sports, including soccer, boxing, football, baseball, lacrosse, skateboarding, hockey, and other high-impact or extreme sports, particularly in youth.
Explosive blasts and other combat injuries. Explosive blasts are a common cause of traumatic brain injury in active-duty military personnel. Although the mechanism of damage isn't yet well-understood, many researchers believe that the pressure wave passing through the brain significantly disrupts brain function.
Traumatic brain injury also results from penetrating wounds, severe blows to the head with shrapnel or debris, and falls or bodily collisions with objects following a blast.
The people most at risk of traumatic brain injury include:
- Children, especially newborns to 4-year-olds
- Young adults, especially those between ages 15 and 24
- Adults age 75 and older
Several complications can occur immediately or soon after a traumatic brain injury. Severe injuries increase the risk of a greater number of complications and more-severe complications.
Moderate to severe traumatic brain injury can result in prolonged or permanent changes in a person's state of consciousness, awareness or responsiveness. Different states of consciousness include:
- Coma. A person in a coma is unconscious, unaware of anything and unable to respond to any stimulus. This results from widespread damage to all parts of the brain. After a few days to a few weeks, a person may emerge from a coma or enter a vegetative state.
Vegetative state. Widespread damage to the brain can result in a vegetative state. Although the person is unaware of his or her surroundings, he or she may open his or her eyes, make sounds, respond to reflexes, or move.
It's possible that a vegetative state can become permanent, but often individuals progress to a minimally conscious state.
- Minimally conscious state. A minimally conscious state is a condition of severely altered consciousness but with some evidence of self-awareness or awareness of one's environment. It is often a transitional state from a coma or vegetative condition to greater recovery.
Locked-in syndrome. A person in a locked-in state is aware of his or her surroundings and awake, but he or she isn't able to speak or move. The person may be able to communicate with eye movement or blinking.
This state results from damage limited to the lower brain and brainstem. This rarely occurs after trauma and is more commonly due to a stroke in that area of the brain.
- Brain death. When there is no measurable activity in the brain and the brainstem, this is called brain death. In a person who has been declared brain dead, removal of breathing devices will result in cessation of breathing and eventual heart failure. Brain death is considered irreversible.
Some people with traumatic brain injury will have seizures within the first week. Some serious injuries may result in recurring seizures, called post-traumatic epilepsy.
Cerebrospinal fluid may build up in the spaces in the brain (cerebral ventricles) of some people who have had traumatic brain injuries, causing increased pressure and swelling in the brain.
Skull fractures or penetrating wounds can tear the layers of protective tissues (meninges) that surround the brain. This can enable bacteria to enter the brain and cause infections. An infection of the meninges (meningitis) could spread to the rest of the nervous system if not treated.
Blood vessel damage
Several small or large blood vessels in the brain may be damaged in a traumatic brain injury. This damage could lead to a stroke, blood clots or other problems.
Injuries to the base of the skull can damage nerves that emerge directly from the brain (cranial nerves). Cranial nerve damage may result in:
- Paralysis of facial muscles
- Damage to the nerves responsible for eye movements, which can cause double vision
- Damage to the nerves that provide sense of smell
- Loss of vision
- Loss of facial sensation
- Swallowing problems
Many people who have had a significant brain injury will experience changes in their thinking (cognitive) skills. Traumatic brain injury can result in problems with many skills, including:
- Speed of mental processing
- Attention or concentration
Executive functioning problems
- Beginning or completing tasks
Language and communications problems are common following traumatic brain injuries. These problems can cause frustration, conflict and misunderstanding for people with a traumatic brain injury, as well as family members, friends and care providers.
Communication problems may include:
- Difficulty understanding speech or writing
- Difficulty speaking or writing
- Inability to organize thoughts and ideas
- Trouble following conversations
- Trouble with turn taking or topic selection
- Problems with changes in tone, pitch or emphasis to express emotions, attitudes or subtle differences in meaning
- Difficulty deciphering nonverbal signals
- Trouble reading cues from listeners
- Trouble starting or stopping conversations
- Inability to use the muscles needed to form words (dysarthria)
People who've experienced brain injury often experience changes in behaviors. These may include:
- Difficulty with self-control
- Lack of awareness of abilities
- Risky behavior
- Inaccurate self-image
- Difficulty in social situations
- Verbal or physical outbursts
Emotional changes may include:
- Mood swings
- Lack of empathy for others
- Changes in self-esteem
Problems involving senses may include:
- Persistent ringing in the ears
- Difficulty recognizing objects
- Impaired hand-eye coordination
- Blind spots or double vision
- A bitter taste, a bad smell or difficulty smelling
- Skin tingling, pain or itching
- Trouble with balance or dizziness
Degenerative brain diseases
A traumatic brain injury may increase the risk of diseases that result in the gradual degeneration of brain cells and gradual loss of brain functions, though this risk cannot yet be determined with any certainty for an individual. These include:
- Alzheimer's disease, which primarily causes the progressive loss of memory and other thinking skills
- Parkinson's disease, a progressive condition that causes movement problems, such as tremors, rigidity and slow movements
- Dementia pugilistica — most often associated with repetitive blows to the head in career boxing — which causes symptoms of dementia and movement problems
Follow these tips to reduce the risk of brain injury:
- Seat belts and airbags. Always wear a seat belt in a motor vehicle. A small child should always sit in the back seat of a car and be secured in child safety seats or booster seats that are appropriate for his or her size and weight.
- Alcohol and drug use. Don't drive under the influence of alcohol or drugs, including prescription medications that can impair the ability to drive.
- Helmets. Wear a helmet while riding a bicycle, skateboard, motorcycle, snowmobile or all-terrain vehicle. Also wear appropriate head protection when playing baseball or contact sports, skiing, skating, snowboarding, or riding a horse.
The following tips can help older adults avoid falls around the house:
- Install handrails in bathrooms
- Put a nonslip mat in the bathtub or shower
- Remove area rugs
- Install handrails on both sides of staircases
- Improve lighting in the home
- Keep stairs and floors clear of clutter
- Get regular vision checkups
- Get regular exercise
Preventing head injuries in children
The following tips can help children avoid head injuries:
- Install safety gates at the top of a stairway
- Keep stairs clear of clutter
- Install window guards to prevent falls
- Put a nonslip mat in the bathtub or shower
- Use playgrounds that have shock-absorbing materials on the ground
- Make sure area rugs are secure
- Don't let children play on fire escapes or balconies