"Memory is the diary that we all carry about with us," Oscar Wilde wrote. But what about when that diary is inexplicably erased?
Amnesia, or memory loss, is a rare and little-understood medical condition that happens to have -- perhaps because it is so mysterious -- great imaginative appeal. What would it be like to wake up and not know who you are? To not be able to recognize friends and family?
Kayla Hutcheson, 19, knows the answer to those questions, although they are difficult for her to articulate. She was struck with amnesia after bumping heads with a teammate at basketball practice in late October 2008. Her memory loss, especially in the beginning, was nearly complete.
Family vacations, high school graduation, holidays were all gone. All the little memories that make each of us whole were deleted from her mind like from a ruined computer hard drive.
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"I wish it would all come back, actually," Hutcheson told "Nightline" during a recent visit to Washington's Walla Walla Community College, where she is a student. "When we'd be sitting around friends or something, be talking about what they did as a child -- I just sit there, 'cause I don't know."
The first day of kindergarten? Or elementary school?
She shakes her head.
"I don't remember doing stuff with them, but I do remember them … well, just the ones I've met, my brother and sister and my parents -- I don't remember my real mom."
Like so many of life's tragedies, it happened out of the blue -- during a simple basketball practice.
She ran into her teammate Jeni Gabriel. The two banged heads.
"I looked at her right away, and I said, 'Are you OK?' and she said, 'Yeah, I'm fine,' and we continued playing," Gabriel recalled.
Apart from a bloody nose, Hutcheson seemed just fine.
But later that night, at home with her teammates, she started acting strange.
"When Jill finally started like, asking her questions, that's when we realized that she didn't know anything," said teammate Nancy Johnson, 18. "She didn't know our names, who we were, where she was, what her name was, how old she was, who her dad was. She didn't know anything."
They took Hutcheson to the emergency room, where she was X-rayed and examined. According to her roommates, she was told she had a concussion -- nothing more.
"It just kept getting worse, she didn't know what a toaster was, she didn't know what fire was," said teammate Jill Haney, 19.
Johnson said the group of friends wasn't sure what to do. "I called my coach and I said 'Coach, it's really serious, you need to see what's going on,'" said Johnson. "Cause she was looking at us with the blankest stare. It was scary."
The coach, Bobbi Hazeltine, said that Hutcheson did not recognize her. "I went over early the next day and she didn't know me," said Hazeltine. "She did not know me."
Haney said it was shocking to realize that Hutcheson couldn't remember her family. "When her dad or her mom or anybody called, she'd hand me the phone -- 'I don't know who it is, you talk to them, Jill, I don't know who they are' -- and that was like heartwrenching, 'cause, like, how do you forget your family?" said Haney.
Hutcheson's father, Bart Hutcheson, made the six-hour drive from home, certain his daughter would come out of it when she saw him.
But Kayla didn't recognize her dad.
Bart Hutcheson cries when he thinks about the moment. "[It was] extremely hard," he says. "But it's, uh, one of the hardest things we've ever faced. You walk into the apartment to introduce yourself to your daughter. We had to make some tough decisions."
Kayla's care was in the hands of Walla Walla family medicine doctor Robert Carmody.
"I didn't want to see her school interrupted if it didn't have to be, and I also wanted her to gain confidence," said Carmody. "Concussions can cause depression and anxiety is stressful, and I've seen that before."
The decision was made to keep Hutcheson in familiar surroundings -- to keep her in school.
A few seconds of home video is the only record that remains of those first dark days for Kayla -- a time when friends described her speech as like that of a toddler.
"She didn't know anything, and all the pictures I would show her -- we started with fruits and vegetables -- she pointed at a banana and said, 'We have one of those at home in our apartment,'" said Hazeltine. "And I said, 'You eat that.' She didn't know how you could eat that. I said 'You peel it,' and she had no concept."
Hutcheson had to relearn everything.
"Apples, oranges, birds, where her classes were," said Hazeltine. "But she relearned."
Hazeltine became Kayla's surrogate mother, tutoring her between classes.
Her teammates and friends did the rest.
"They had 'Kayla Care,'" said Hazeltine. "Those three [Johnson, Haney and roommate Jaimie Berghammer] would get up and talk, 'OK, who's got her lunch, who's got her here, who's taking her notes, who's taking her to class,' etc. And it lasted a couple of months, and it's just awesome."
Hutcheson showed "Nightline" a stick-figure drawing hanging on the refrigerator. "That was my first drawing," she said.
Sitting in class one day, she asked a friend why the man up front was writing on the wall and talking so loud. She didn't understand he was the teacher.
Hutcheson said day-to-day life is still intimidating. "There's a lot of things I don't understand when the teachers talk," she said, "so my friends help me, like, understand."
She's coming back though, slowly, relearning the basics of life. Relearning basketball. Relearning who she is.
Her father set up a digital picture frame in her bedroom, loaded with old photos to help.
"So I guess I broke my ankle," said Hutcheson, looking at a childhood photo. She said the photos have helped her to recover some memories.
"It's kind of helped me remember some people, point out who is who -- that's the athletic director at my high school."
A picture frame, school and friends -- this is Kayla's therapy.
"Nightline" asked Bart Hutcheson if his daughter is getting the care she needs, or whether she should she see a neurologist or another specialist.
"I just don't know what they would do," Hutcheson said. "From what few doctors I've talked to, what research I've done, nobody knows anything about it."
Kayla's family and coach have followed the advice of their local family practice doctor, who believes seeing a specialist may only upset Kayla.
Hutcheson's recovery hasn't been as clean as friends and family might think, she acknowledged.
"I get confused a lot," she said.
ABC News spoke to several of the nation's leading neurologists. All of them thought Kayla's case was exceptionally rare and in need of a great deal of further study.
"You generally do not get a loss of information about the world, about words, factual information from a concussion or even from a moderately severe head injury," said Dr. Kenneth Perrine of the Northeast Regional Epilepsy Group at the Weill-Cornell College of Medicine.
Hutcheson described the emotional impact of her injury.
"Not so much angry, just more frustrated," she said. "I am sad and, like, because there's a lot of great people that know me, and I don't remember them."
Her teammate Nancy Johnson, there from the beginning, wrote a poem about her lost friend, a 19-year-old struggling to find herself again.
"Kayla, are you in there, the girl I once knew? Now we are both strangers, our familiarities few.
"Kayla, you are next to me but your mind is gone. When will you come back to me, please tell me how long?
"Kayla, I love you, please don't ever forget. My name is Nancy, I am glad we just met."
For her part, Hutcheson strikes an upbeat tone when asked about her future.
"I want to go on and play basketball, and be a physical therapist," she said. "Hopefully the memory will come back."
If it doesn't, Hutcheson has new memories -- memories drawn from pictures of her, living a life she can't remember. It's like another class to be endured. Call it History of Kayla, 101.