Early in the second period of Clarion-Limestone High School's first football game of the season Sept. 1, running back Matthew Hetrick was knocked to the turf after a violent helmet-to-helmet collision.

Bob Donaldson, Post-Gazette Dr. Michael Collins, right, gives Clarion-Limestone High School senior Matthew Hetrick, second from right, and his father Derry Hetrick, left, the results of his latest ImPACT test three weeks after Matthew's latest sports concussion suffered during a football game. Dr. Collins decided to limit Matthew's school attendance due to the continuing poor results of the test. Family friend Rochelle Beckwith sat in on the conference. Click photo for larger image.

Matt, a 17-year-old senior, played the rest of the quarter, but doesn't remember it, or anything else until the next morning. Matt was back in class the following Monday, but he shouldn't have been, said Michael "Micky" Collins, 37, assistant director of the UPMC sports concussion program.

Ever since the incident, Matt has had headaches -- sometimes pretty severe headaches -- every day. He also reports occasional dizziness and nausea.

The headaches worsen in the afternoon, especially when he has to think hard to solve problems in his pre-calculus class, Matt told Dr. Collins, who has a Ph.D. in clinical neuropsychology.

"I'm sitting in class in the last period of the day, and I just shut down," he said.

His son's personality has changed a bit since the incident, his dad said.

"He's just been more grumpy," Derry Hetrick said. "I don't know if it is because he isn't playing football."

Matt agreed. "I hate not playing football," he said. "I take it out on everybody else."

But Dr. Collins said grumpiness is a symptom of a concussion, though not one many people recognize.

"It's not as if he's wearing a cast on his head," Dr. Collins said. "Nobody knows this."

Dr. Collins ordered a CT scan and an MRI for Matt, but predicted they would show no abnormalities.

"Concussion is a functional injury," he said. "You can't see that when you take a picture of [the brain]."

Fortunately for Matt Hetrick, Clarion-Limestone is one of about 2,000 high schools nationwide (250 in western Pennsylvania) that use a program developed by UPMC to diagnose concussions, and to measure the extent to which they have impaired the athlete. The program also is used by many colleges and NFL teams.

It is badly needed. About 1.5 million football players in the United States -- about 10 percent of all players -- will suffer concussion injuries this year.

Before UPMC developed ImPACT (Immediate Postconcussion Assessment and Cognitive Testing), the principal means of testing for a concussion was to give the player smelling salts, wave some fingers in front of his face, and see if he could correctly identify the number of fingers.

Coaches and trainers also relied heavily on the reports of symptoms by injured players. But this is unreliable, said a recent paper in the American Journal of Sports Medicine, because the athletes want to play, and they'll fib to get back into the lineup.

"An athlete's apparent fear of removal from a game or of losing his or her position on the team may tempt some athletes to deny or underreport postconcussive symptoms," said the paper, which was authored principally by Derk Van Kampen of the orthopaedics department of the University of Groningen in the Netherlands, and Mark Lovell, director of the UPMC sports concussion program. Dr. Collins and two other UPMC colleagues were coauthors.

ImPACT is a 20- to 25-minute video game played on a computer that tests cognitive skills such as memory and reaction time. If the athlete has taken a baseline test, a post-concussion ImPACT test can determine the extent of impairment or recovery.

In Matt Hetrick's case, the results of the ImPACT test were dramatic. He scored in the 88th percentile in memory in the baseline test he'd taken a year ago, but was in the first (lowest) percentile after his concussion. Matt's reaction time fell from 22nd percentile to the first percentile.

But though Matt's decline has been substantial, it likely only will be temporary. Matt's symptoms should disappear in about two months if he takes proper care of himself, Dr. Collins told Matt and Derry.

That means no physical activity, and only half days at school for the next couple of weeks, Dr. Collins said, writing the appropriate notes to Matt's teachers.

For Matt to go to school full time while he was recovering from his concussion "is like trying to run on a broken ankle," Dr. Collins said.

Concussion injuries, like broken bones, need time to mend, he said. Straining to think when you are suffering from a concussion can make things worse.

"You are doing the damage when you hit the wall," Dr. Collins said.

Football is over for Matt for good, but he should be cleared to play by the time baseball season rolls around, Dr. Collins said.

"I'm glad you're doing what you're doing," Derry Hetrick told him. "It's not worth risking the rest of his life."

Most of the concussions he's dealt with are not as severe as Matt Hetrick's, Dr. Collins said. Matt is having a harder time coming back because this is his fourth concussion in six years. With each new concussion, the symptoms of concussion came on sooner, lasted longer, and were more pronounced.

This last wouldn't have been so severe if the earlier concussions had been properly diagnosed and treated, Dr. Collins said.

The ImPACT test makes it possible to diagnose much more accurately. The current test is good for athletes 11 years of age and up. The UPMC sports concussion staff is developing a test for children as young as 5 years old.

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Correction/Clarification: (Published Sept. 22, 2006) In this story "Sidelined by Concussions" about the UPMC sports concussion program, Dr. Michael Collins recommended that Matt Hetrick go to school for half days for two weeks while recovering from his concussion, not two months as originally stated in the article.