''I remember it happening, but after that, nothing. It's like it never existed," Maria Carrillo High junior Alex Wrenn said of the concussion he suffered last August.
Wrenn, a nose tackle for Maria Carrillo's varsity football team, was hit in the chin with the top of a football helmet during practice.
"I know what happened, I remember getting hit," he said. "But remembering it, I feel like it was something I watched. Not like it was me."
In the three weeks that followed, Wrenn had a hard time focusing in class and on assignments.
"I was missing homework assignments, forgetting to do them," he said. "And information I learned before was difficult to remember."
Robert Neid, a sports and family medicine physician at Kaiser Permanente Hospital in Santa Rosa, said such a side effect is not unusual.
"Common symptoms are a foggy head, where it's kind of hard to remember or focus (and) amnesia," he said.
Concussions, although not day-to-day occurrences on the field, are not unusual in intense, high-level sports.
"With any physical endeavor, there is risk," said Jay Higgins, who coaches the Maria Carrillo football team. "And it's our job to protect the kids. One way we do that is by getting the best equipment and making sure it's properly fitted."
Although high-quality equipment is better for preventing most injuries, there are some common misconceptions.
"No helmet has ever been shown to prevent a concussion," Neid said. With or without a helmet, "it's a shock to the head."
Higgins emphasized that although the players are equipped with the best gear, avoiding a concussion is all about technique.
Wrenn agreed: "It depends on how you stand and how you get hit."
Although it seems awareness has risen because of media attention on long-term studies of effects of repeated concussions in athletes, many remain unidentified.
"I would say about 90 percent aren't diagnosed," Neid said. "No one can see a concussion, so it is hard" to catch.
He advised that in any case, athletes should watch for symptoms and try to avoid getting hit similarly again.
These studies, which show athletes with significant brain damage after a lifetime of concussions, raise some concern for the parents of student athletes.
Wrenn said his mother "was really hesitant" about letting him resume playing.
"The first few weeks after Alex's concussion, you might say I was on 'full alert,' regularly asking, observing and evaluating his situation," said Wrenn's mother, Denise Gentry. "With the doctor's directions and the coaches' carefulness that any jeopardy to (Alex) was well managed."
Although the studies disquiet some parents, Higgins says these studies don't directly apply to the high school athletes.
"These studies were done on athletes that played football professionally. They had a lifetime of serious collisions. They were getting hit much harder than any high school player," he said.
"Ultimately, there are so many positive, formative, developmental benefits to (Alex) playing football; I believe they outweigh the risk," Gentry said.
Although Wrenn was affected by his injury, he was unfazed by the whole experience.
"I was glad when I could play again," he said.
He acknowledges the risk but says it has been a learning experience for him as a player.
"The possibility is always there, but I'm careful and won't let myself get hit like that again," he said.