Cinematic amnesia, while entertaining, is not very accurate at all. The traditional "who am I, where am I??" perception of amnesia is false. People who have it do retain the knowledge of who they are and can generally tell you where they are also. In addition, long term memories usually arent damaged, so the idea of having the slate wiped clean is also false. In the movie 50 First Dates, amnesia is used just for the convenience of the story, not to show what it actually does. The character played by Drew Barrymore got into a car accident on her birthday multiple years previous to when Adam Sandler's character comes to know her. Her experience from her birthday is perfectly preserved, along with everything up until then. Her family goes to crazy lengths to make every day her birthday in order to make her life seem normal to her. Already in the film there are a plethora of errors. A car crash with head trauma wouldnt cause amnesia. As the original post stated, strokes, infections, virusus, and the like cause amnesia. Another flaw: if she actually did get amnesia, she wouldnt remember much of the day it happened or the few days previous. Her short term memory up until the accident is perfect, but she cant remember anything at all after it. People with amnesia still remember some things, like the passage of time on a day to day basis. When Adam Sandler comes into the story, we are led to believe that her memory resets overnight and that she can only remember things from that day until she falls asleep. This also is completely false. While it may make the movie more romantic and sad, amnesia doesnt work like that what so ever. Amnesia is a progressive condition, you may remember some things, but not others. The video tape Adam makes for her is...creative. While it would provide some information for the patient on what happened, likelihood is that they wouldnt recall watching it a short while after it finished. Once again, this wouldnt allow an individual with severe amnesia to live normally for a day because amnesia is progressive. It simply doesnt reset every night at 12:00.
My grandmother has the beginnings of amnesia related to dementia or Alzheimers possibly (we dont know which yet, its in the extremely early stages). Often times she wont recall telling a story or saying something, so she'll say it again. That becomes somewhat awkward, especially for her. My other grandma had a stroke, and amnesia related to that came on very quickly. She wouldnt recall making breakfast or even (in the later stages) who i was or what my relation to her was. At that point, it had practically turned into Alzheimers with dementia sadly soon to follow. Movies and TV dont portray amnesia like it actually is, but even though its inaccurate, it makes for a good and creative story line.