Head injury occurs when an outside force hits the head hard enough to cause the brain to move violently within the skull. This force can cause shaking, twisting, bruising (contusion), or sudden change in the movement of the brain (concussion).
- In some cases, the skull can break. If the skull is not broken, the injury is a closed head injury. If the skull is broken, the injury is an open head injury.
- In either case, the violent jarring of the brain damages brain tissue and tears nerves, blood vessels, and membranes.
- The severity of this damage depends on the location and force of the blow to the head.
Damaged brain tissue does not work normally.
- The brain has many different functions in the body, and any of them can be disrupted by this damage.
- Not all brain damage is permanent. Like all body organs, the brain can heal to a certain extent.
- Even this healing may not bring the brain’s function back to what it was before the injury.
Even a relatively mild head injury can cause prolonged or permanent declines in cognition. (Cognition is the processes of thinking, remembering, understanding, reasoning, and communicating.) Head injury can also cause changes in emotions or behavior.
- Together, these changes are known as dementia.
- The nature of dementia in head-injured persons varies greatly by type and location of head injury and the person’s characteristics before the head injury.
After head injury, a person may have symptoms such as changes in personality, emotional problems, and difficulty making decisions or solving problems.
- The exact symptoms depend on the parts of the brain that are injured.
- Likewise, the severity of symptoms can be related to the severity of the brain injury, but this is not always true.
- If the injury is not too severe, these symptoms may get better over time.
Direct damage to brain tissue and surrounding areas accounts for only part of the problems in head injury. The resulting bleeding (bruising), fluid collection (hydrocephalus), and infection can also damage the brain. A common complication is epilepsy (seizures).
Dementia after head injury is a significant public health problem.
- In the United States, roughly 2 per 1000 people each year have some kind of head injury. Many do not seek medical care.
- Between 400,000 and 500,000 people are hospitalized in the United States every year for head injury.
- Younger people are more likely to have a head injury than older people. Head injury is the third most common cause of dementia, after infection and alcoholism, in people younger than 50 years.
- Older people with head injury are more likely to have complications such as dementia. Children are likely to have more severe complications.
- Men, especially younger men, are more likely than women to have a head injury.
Dementia in Head Injury Causes
The following are the most common causes of head injury in civilians:
- Motor vehicle accidents (50%)
- Falls (21%)
- Assault or gunshot wound (12%)
- Sports, such as boxing (dementia pugilistica), or other recreational activity (10%)
- Use of alcohol or other substances is a factor in about half of these injuries.
Certain groups are more likely than others to sustain head injury.
- In children, bicycle accidents are a significant cause of head injury.
- Most head injuries in infants reflect child abuse. A common name for this is shaken baby syndrome.
- Elderly persons are especially likely to injure themselves by falling.
Dementia in Head Injury Symptoms
Dementia-related symptoms in head injury are those that affect thinking and concentration, memory, communication, personality, interactions with others, mood, and behavior.
- These are only some of the symptoms that might be experienced after a head injury.
- Individuals experience different combinations of these symptoms depending on the part of the head injured, the force of the blow, the damage caused, and the person’s personality before the injury.
- Some symptoms appear rapidly, while others develop more slowly.
- In most cases, symptoms have at least started to appear in the first month after the injury.
Symptoms of dementia in head-injured persons include the following:
- Problems thinking clearly
- Memory loss
- Poor concentration
- Slowed thought processes
- Irritability, easily frustrated
- Impulsive behavior
- Mood swings
- Inappropriate behavior in social situations
- Grooming and dressing eccentric or neglected
- Restlessness or agitation
- Aggression, combativeness, or hostility
- Vague, nonspecific physical symptoms
Some people develop seizures after a head injury. These are not part of the dementia, but they can complicate diagnosis and treatment of dementia.
Major mental disorders may develop after head injury. Two or more of these may appear together in the same person.
- Depression – Sadness, tearfulness, lethargy, withdrawal, loss of interest in activities once enjoyed, insomnia or sleeping too much, weight gain or loss
- Anxiety – Excessive worry or fear that disrupts everyday activities or relationships; physical signs such as restlessness or extreme fatigue, muscle tension, sleeping problems
- Mania – State of extreme excitement, restlessness, hyperactivity, insomnia, rapid speech, impulsiveness, poor judgment
- Psychosis – Inability to think realistically; symptoms such as hallucinations, delusions (false beliefs not shared by others), paranoia (suspicious and feeling of being under outside control), and problems thinking clearly; if severe, behavior seriously disrupted; if milder, behavior bizarre, strange, or suspicious
- Obsessive-compulsive symptoms – Development of obsessions (uncontrolled, irrational thoughts and beliefs) and compulsions (odd behaviors that must be carried out to control the thoughts and beliefs); preoccupation with details, rules, or orderliness to such a degree that the larger goal is lost; lack of flexibility or ability to change
- Suicide risk – States feelings of worthlessness or that life is not worth living or that world would be better off without him or her, talks about suicide, states intention to commit suicide, develops plan to commit suicide
When to Seek Medical Care
Any of the symptoms and signs described in the Symptoms section warrants a visit to the person’s health care provider. This is true regardless of whether the person has a known head injury. Be sure the health care provider knows about any falls or accidents that could have involved even a mild head injury.
Medical Author: Julia Frank, MD
Medical Editors: Nestor Galvez-Jimenez, MD; Francisco Talavera, PharmD, PhD; Helmi L Lutsep, MD
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