RELATED STORIES • Brain injury: One teen's story BRAIN & NERVOUS SYSTEM Head Injury • Concussion • Traumatic brain injury

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A traumatic brain injury is usually the result of a sudden, violent blow to the head. Such a blow can launch the brain on a collision course with the inside of the skull. The skull itself can often withstand a forceful external impact without fracturing. The result — an injured brain inside an intact skull — is known as a closed-head injury.

A brain injury may also occur when a projectile, such as a bullet, rock or fragment of a fractured skull, actually penetrates the brain. This type of injury is far less common than is the closed-head variety.

The severity of brain injuries can vary greatly, depending on the part of the brain affected and the extent of the damage. A mild brain injury may cause temporary confusion and headache, but a serious one can be fatal.

About 1.4 million Americans sustain a traumatic brain injury each year. Luckily, more than 75 percent of these injuries are mild concussions. But even minor brain injuries can cause long-term problems.

Your brain controls your movements, behaviors, thoughts and sensations. Not surprisingly, then, a brain injury can affect many different aspects of your physical and emotional well-being.

Most symptoms of a brain injury appear immediately or shortly after a blow to the head. In many cases, however, the symptoms are subtle and easy to miss — even for the person who's been injured.

Signs and symptoms of a mild brain injury can include:

• Brief period of unconsciousness
• Headache
• Confusion
• Dizziness
• Sensory problems, such as blurred vision, ringing in the ears or a bad taste in the mouth
• Mood changes
• Memory or concentration problems

If the injury is moderate to severe, the list of signs and symptoms grows to include:

• Persistent headache
• Repeated vomiting or nausea
• Convulsions or seizures
• Inability to awaken from sleep
• Dilation of one or both pupils of the eyes
• Slurred speech
• Weakness or numbness in the extremities
• Loss of coordination
• Increased confusion or agitation

Children with brain injuries may lack the communication skills to report headaches, sensory problems, confusion and similar symptoms. Instead, they may refuse to eat and appear listless or cranky. Their sleep patterns and school performance may change, and they may lose interest in favorite toys or activities.

Problems associated with traumatic brain injuries often come in two stages. The original impact may bruise portions of the brain or directly sever nerve connections. The second stage of the injury occurs when the tissue at the injury site begins to swell.

It is normal for injuries to cause swelling. Think of the last time you got a bad bruise. In addition to being colorful, the bruised area probably became tender and swollen. Now imagine that happening on a larger scale inside a bony confined space.

Inside the skull, there's no place for this swelling to go, so the pressure on the brain increases. Intracranial pressure must be monitored closely because it can result in additional damage to the brain.

Half of all traumatic brain injuries are caused by collisions involving cars, motorcycles and bicycles. Traumatic brain injuries inflicted by firearms have the highest likelihood of causing death. Almost two-thirds of firearms-related brain injuries are self-inflicted. Gunshot wounds to the head are fatal 90 percent of the time.

Among older people, falls are the leading cause of traumatic brain injuries. Infants and small children are also vulnerable to traumatic brain injuries, particularly as a result of being shaken violently.

• Age. The risk of traumatic brain injury is highest in two age groups — adolescents (ages 15 to 19) and small children (ages 0 to 4).
• Sex. Males are 1.5 times as likely as females to suffer a traumatic brain injury.

To stay on the safe side, you should always get checked by a doctor if you have suffered a blow to the head. Anyone with signs of moderate or severe brain injury — such as convulsions, weakness or numbness in the extremities, repeated vomiting, or slurred speech — should receive emergency medical care. These types of brain injuries can quickly become life-threatening.

Emergency medical personnel assess the severity of a brain injury by seeing how well the injured person can follow directions to blink his or her eyes or to move extremities. The coherence of the person's speech also provides important clues.

Imaging tests often are crucial in determining the extent of injury. Skull and neck X-rays can check for bone fractures or spinal instability. Computerized tomography (CT) scans can uncover evidence of:

• Bleeding in the brain (hemorrhage)
• Large blood clots (hematomas)
• Bruised brain tissue (contusions)
• Brain tissue swelling

Some of the complications that can occur with traumatic brain injuries include:

• Coma. A person who is unconscious and unresponsive is in a coma. This situation typically lasts only a few days or weeks. After this time, some people gradually awaken, while others enter a vegetative state or die.

  People in a vegetative state often open their eyes and may move, groan or show reflex responses. Despite this, they are still unconscious and unaware of their surroundings. Anyone in a vegetative state for more than a year rarely recovers.

• Seizures. Some people who have had a traumatic brain injury will experience at least one seizure during the first week after the injury. However, this doesn't appear to increase their chances of developing epilepsy.
• Infections. Skull fractures or penetrating wounds can tear the membranes (meninges) that surround the brain, letting in bacteria. Infection of these membranes (meningitis) can be especially dangerous because of its potential to spread to the rest of the nervous system.
• Nerve damage. Injuries to the base of the skull can damage facial nerves, causing paralysis of facial muscles or damage to the nerves responsible for eye movements, resulting in double vision.
• Cognitive disabilities. Thinking, reasoning, problem solving, information processing and memory are all cognitive skills. Most people who have had a severe brain injury will experience cognitive problems. The most common of these impairments is short-term memory loss. That means the injured person recalls information from before the head trauma but has to struggle to learn new information after the head trauma.
• Sensory problems. A persistent ringing in the ears or difficulty recognizing objects can occur. Hand-eye coordination often is impaired, which can make people appear to be clumsy. If the part of the brain that processes taste or smell has been damaged, the person may perceive a bitter taste or a bad smell. He or she may also have blind spots or see double.
• Difficulty swallowing. A person with a brain injury may need to be fed through a tube during the early part of his or her recovery.
• Language difficulties. Communication problems are common. Some people who have had brain injuries have trouble with spoken and written language, while others have problems deciphering nonverbal signals.
• Personality changes. Brain injuries typically interfere with impulse control, so inappropriate behavior is often present during recovery and rehabilitation. The injured person's unstable emotions and impaired social skills pose the greatest coping challenge for many families.
• Alzheimer's or Parkinson's disease. A traumatic brain injury appears to increase the risk of eventually developing Alzheimer's disease and, to a lesser degree, Parkinson's disease. The higher the frequency and severity of the injuries, the greater the risk.

Fewer than half the people who suffer severe traumatic brain injuries need surgery to remove or repair the damaged portions of their brains. In some cases, there is a collection of blood between the skull and the brain. This is called an intracranial hematoma, which must be surgically drained.

Surgery may also be performed to drain the excess fluid that has accumulated in reaction to the trauma itself. While swelling is a natural reaction for body tissue that has been injured, it can cause additional damage to the brain by increasing the pressure inside the skull. Medications also can be used to decrease this pressure.

Most people who have had a significant brain injury will require rehabilitation. They may need to relearn basic skills, such as walking or talking. The overall goal is to improve their abilities to function at home and in the community.

Follow these tips to reduce the risk of brain injury:

• Always wear a seat belt in a motor vehicle. Small children should be secured in child safety seats or booster seats. Depending on their size, older children may be adequately restrained with seat belts.
• Never drive under the influence of drugs or alcohol.
• Store firearms, unloaded, in a locked cabinet or safe. Store bullets in a separate location.
• Wear a helmet while riding a bicycle, skateboard, motorcycle, snowmobile or all-terrain vehicle. Also wear head protection when you bat or run bases, ski, skate, ride a horse, or play a contact sport.
• Avoid falls by installing safety features in your home — such as handrails on stairways, nonslip mats in the bathtub and grab bars in the bathroom. An exercise program can improve your strength, balance and coordination. Regular vision tests also can help lower the risk of falling.

A brain injury often erases your memory of events that occurred just before your injury. It can also make it more difficult for you to remember new information and learn new tasks. While some memory problems may diminish over time, others may be permanent.

As they slowly recover and adjust, some people who have had brain injuries carry cue cards that list coping strategies, such as:

• Slow down.
• Stop and think.
• Break it down, step by step.
• Ask questions.
• Do not assume.
• Pay attention to details.
• Take a break.
• Think of other things to try to problem solve.

Many people also find it helpful to carry a calendar for planning and organizing daily activities, step by step. It can serve as a reminder of uncompleted tasks and as a storage site for information you might otherwise forget.