Each year 10,000 people in the United States injure their spinalcords and heads and another 500,000 receive head injuries severe enough to require hospitalization. "The impact of these sudden, serious injuries can be devastating," says Jackie Heath, coordinator of the spinal cord and head-injury-prevention program at the UC Davis Medical Center. "A survivor of severe brain injury faces five to 10 years of intensive services. In addition to physical changes, injured persons and their families must deal with sudden social, emotional and vocational changes." The most frequent cause of head and spinal-cord injuries are motor-vehicle crashes. Teen-agers and young adults, in particular, are at high risk for these injuries. Concerned about a rise in injuries among young adults, neurosurgeons around the country have developed an education program to alert teens to high-risk behavior and its dangerous consequences. In the two years the Sacramento program has been established, 11,000 teen-agers have learned about the dangers of risky behavior involving automobiles, all-terrain vehicles, alcohol, diving and other action sports.