When doctors describe the brain and what happens to it when it is injured, they tend to conjure up food images.

"The brain is like Jell-O," said Max Root, medical director of the Intermountain Rehabilitation Center at Utah Valley Regional Medical Center. "It is so delicate that if you touch a finger on its surface you can destroy it."Walter F. Haemmerle, medical director of the Quinney Rehabilitation Institute at Holy Cross Hospital puts it this way: "The brain is the consistency of custard."

Keep the image of a Jell-O- or custardlike brain floating in cerebral-spinal fluid in mind and consider the scenario of what likely happened to Rich Wiebke's brain when he ran into a tree two years ago at a Utah ski resort: The force of the impact with the tree caused Wiebke's brain to slam against the front of his skull. His brain bounced off that bony structure and banged into the back of his head.

That's what happens to the brain whether the head hits a tree, dashboard, windshield or sidewalk. It's also what happens when a person's head experiences a sudden violent motion - when a child is shaken too vigorously or a person gets whiplash. And it's what happens when there is a blow to the head.

Often the brain will slosh back and forth between the front and back surfaces of the skull several

times before it stills. In some cases the brain twists on its stalk, allowing different areas of the brain's surface to be damaged.

Each time the brain slams into the bony surfaces of the skull there is potential for damage. The surface of the brain gets bruised and little hemorrhages appear; brain tissue may be torn. Nerve fibers are stretched, torn or even sheared.

In more serious injuries, bleeding may also occur within the brain. Damage to the brain often causes it to swell, which can cause more damage than the original injury.

It is common for a person to lose consciousness briefly; that happens when the brain's activating system is momentarily knocked out.

"After coming out of unconsciousness and becoming more aware of the environment, a person may become confused, disoriented and agitated because they can't process information," Root said.

Commonly damaged portions of the brain are the frontal and temporal lobes, the brain stem and the corpus callosum, a thick band of neural tissue connecting the two hemispheres of the brain. The problems that may result are many and varied - ranging from physical to cognitive problems - and depend on the severity of the injury.

Physical problems include headaches, dizziness, fatigue, ringing in the ears, numbness or paralysis, loss of balance. Many such problems subside with time - three months to one year, Haemmerle said.

Cognitive, emotional and behavioral problems, which may take much longer to discern as well as correct, can be summed up by an overall decrease in the speed, efficiency, execution and integration of mental processes.

Abilities and behaviors impaired often include:

- Short- and long-term memory.

- Ability to learn, plan and organize.

- Ability to process information and to shift attention from one task to another.

- Ability to integrate information and engage in abstract and creative thinking.

- Loss of emotional control.

- Change in personality.

- Language, perception, sensory and motor functions.

"A person may be able to tell you what he did in high school . . . but have difficulty telling you what he did yesterday," Haemmerle said.

Drugs are given to reduce brain swelling; sometimes surgery is necessary to drain bleeding. Often, problems that result from a head injury aren't recognized at first; following initial recovery a patient is told he or she will be fine and is sent home with the advice to take it easy for while.

"When they go home and start having problems, they think they are going crazy," Haemmerle said. "When the system starts getting pushed they begin having trouble. Things unravel for them."

Diagnostic tests - CAT scans and Bar tests, for example - often fail to reveal nerve damage in the brain. Haemmerle relies on extensive testing that pushes the system to help determine the extent of an individual's problems following a head injury.

It is difficult to predict how a person will recover from a head injury, doctors say.

"There is still so much we don't know about the brain," Root said. "We haven't scratched the surface of the way the brain works. Our level of understanding of the brain is still so primitive. Now we are just giving the best shot of theories and practices."

Brain tissue cannot be regenerated, but some researchers theorize that when a part of a brain is damaged, other parts can learn to take over activities of the damaged portion, Root said.

"In rehabilitation we gear ourselves to brain relearning through repetition," Root said.

Rehabilitation plans are tailored to a patient's needs. Progress occurs in chunks - the most rapid advances occurring in the six months following the injury. Improvement can continue for years.

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Heading off a head injury

It's not always possible to avoid getting a head injury. When you fall tens or hundreds of feet off a cliff, even the best of helmets may not help protect your head.

But in other situations there are definite steps you can take to prevent or lessen a head injury:

-Wear a seat belt. Buckle childre up or make them ride in a car seat. If you're buying a new car, the National Head Injury Foundation recommends buying one equipped with protective air bags.

-Don't drink and drive.

-Wear protective headgear when participating in a range of recreational activities, including bicycling, horseback riding, engaging in contact sports, rock climbing, riding a motocycle, etc.

-Don't drive into water without knowing how deep it is or wheater there are any submerged objects hidden from view below the surface.

-Don't shake a small child.

-Take steps to fall-proff your home if you have small children; block off access to stairs and high places.

-Keep guns out of the reach of children. Keep guns and other hand weapons securely locked up so they are more difficult to obtain in a heated moment.