Amnesia is a fascinating condition, and as such it comes up commonly in popular culture. It’s such a wonderful (and by wonderful, I mean wonderfully over-used) plot device – after an unfortunate whack on the head by a large blunt object, characters can be caught in precarious positions as they struggle to recall one key piece of information, acting as a detective of their own minds. Sometimes the amnesia is temporary, lasting long enough for one 22-minute television program; in others, their amnesia is a lifelong problem.

Yet there’s one type of amnesia that is rarely covered in the media. It strikes spontaneously, without warning or easily detectable cause. Its victims go through the normal conditions for amnesia, forgetting a good portion of their past and becoming unable to form new memories. They are disoriented, confused, lost. But here’s the surprising part – within 24 hours, the amnesia is gone and previous mental abilities return. It’s called Transient Global Amnesia (TGA), and is among the more harmless (though bizarre) conditions one can have.

No one knows the exact cause of TGA, but there are a few (highly educated) guesses out there. First, it occurs most commonly in older people – while it has an overall occurrence of about five per 100,000 per year for all ages, the rate is quadrupled for those over the age of 50. In general, it appears to be caused by stress or emotional trauma – but then again, what isn’t? Also, many people who experience TGA also suffer from migraines, so it is thought that TGA may be a form of a mega-migraine-like headache.

People who are struck with TGA retain all of their normal cognitive abilities – they can still talk and function normally, except anything they learn will be forgotten within a few minutes because information in short-term memory is somehow prevented from being stored in long-term memory. Also, some recent history is temporarily lost, ranging from a few hours to 40 years. Naturally, this situation causes people to become very disoriented. Someone with TGA will constantly be asking for basic information, such as “where am I?”, “what is going on?”, or “what happened to the good old days?” Providing them with the answers does not help at all – though they may grasp that they are having short term memory loss, in a few minutes… well, you know.

The worst of TGA does not last long (only a few hours), but can take up to a day or more to fully recover, much like a hangover. Unless the TGA is masking some sort of more serious condition, the worst that can happen is that one permanently forgets what happened during the state of amnesia. So if one of your loved ones suffers from TGA, remember to inform them of that fact while they’re not having an episode… otherwise they may never know.