By Kay Quinn, KSDK-TV, September 10, 2007

Get a mental picture of a snow globe, one of those glass balls with white bits of Styrofoam or glitter that float when shaken.

It''s a good example of what happens inside the brain when someone suffers a concussion, says Dr. Mark Halstead, a sports medicine physician at St. Louis Children''s Hospital and Barnes-Jewish Hospital. He also is a physician for the St. Louis Rams.

"The snow is trying to settle down in that snow globe," Halstead said. "That''s kind of what''s going on inside the brain. It''s just the signals are all kind of messed up. They just really don''t know how to process things."

Halstead says concussions are more serious than doctors thought in the past. It''s important information, especially for parents with children who participate in sports or activities in which there''s a chance of suffering a violent shake or blow to the head.

"There was a study that was done about six years ago that looked at college students that had concussion," Halstead said. "What they saw is that even if they weren''t having symptoms of their concussion, they actually had difficulty processing things for seven days after."

Meghan Hei, 10, of Florissant wasn''t playing an organized sport when she suffered a concussion that sent her to the hospital. She was playing basketball with her siblings and cousins in early April when she fell and hit her head.

Her brother led her into the house, where her parents initially blamed her tearfulness on the fact that she had fallen. But in the next half-hour, she started to feel worse, not better.

"My wife came in and said, ''Meghan can''t see,''" remembered Greg Hei, Meghan''s dad, who is also a nurse. "She never really passed out. She kind of went into the other room and was sitting down just not being herself."

The Heis rushed Meghan to an emergency room, where doctors diagnosed a concussion.

Halstead says experts in his area of specialty report seeing longer-lasting symptoms after concussions.

"The common misconception is that you have to lose consciousness to have a concussion, but that''s actually far from the truth," Halstead says.

Typical symptoms include dizziness, headache, weakness, changes in vision, nausea and vomiting.

Diagnosing a concussion can be difficult, even for doctors. CT or MRI scans of the brain may not show any abnormalities, yet the brain may still have suffered an injury.

Halstead says he is among a growing number of physicians relying on a new computerized test to help diagnose concussions. It measures memory and recall of words and shapes, and can be a powerful indicator of the severity of concussion.

Deciding when a blow to the head requires a trip to the doctor can be tricky. Halstead says anyone with even mild symptoms should be checked out.