In fiction, that is.
Forget You, by Jennifer Echols, Zoey is in a car accident. She hits her head. And the next day, she can't remember much of anything about the night before. Which is unfortunate, because Doug Fox, her nemesis, is acting like a lot went down.
Post-traumatic amnesia is not uncommon in cases of Traumatic Brain Injury (TBI). Basically, the person is unable to store new memories for a period of time after the accident. Zoey actually has a mixed anterograde/retrograde presentation. She can't remember some events leading up to the accident (retrograde amnesia) and she can't remember most of the events that occurred in the hours after the accident (anterograde amnesia). Hence the drama!
In reality, of course, amnesia isn't that romantic or compelling. It's sad and frightening and frustrating.
Bumps on the head, zaps to the skull, and other physical injuries to the brain lead to organic amnesia, and so can Alzheimer's disease, oxygen deprivation, stroke, and long-term alcohol abuse. But then there are some psychological forms of amnesia, often associated with dissociation. These are, as you might expect, more controversial, but they basically involve the mind trying to protect itself by repressing memories of traumatic events.
What amnesia usually doesn't involve (with the exception of dissociative fugue) is the loss of self-identity. People with amnesia don't usually forget who they are (and here is where reality departs so drastically from fiction).
Amnesia is well-covered in novels and movies, so if you've got an amnesia story, you might want to make sure you've got an original twist (my agent is probably laughing at me right now).
How about you? What are some of your favorite amnesia-fic-picks? Any specific to YA? Have you read Forget You or Memoirs of a Teenage Amnesiac? Did you wonder about the accuracy of the portrayal? Have you read or watched things where amnesia seemed like a contrivance? Have you read or watched things where it didn't matter whether it was medically accurate or not, because it was just so deliciously good?