Saw a guy today in the acute medical unit who had been brought in by his relatives yesterday in a state of considerable confusion. He did not know where he was, or the year, and he kept repeating himself. This morning when I saw him, he was once again a model healthy 65 year old man, the mysterious malady having evaporated without trace. He remembered being in the car being given a lift down to visit his grandchildren, and then he remembered being in hospital. A quick examination revealed nothing out of the ordinary. Hmm.
The consultant turned to me and asked me what I thought. My immediate thought was a transient ischaemic attack~(TIA) – a type of temporary stroke when an area of brain doesn’t get enough oxygen, but recovers fully inside of 24 hours. He grinned a ‘nice try’ smile and shook his head. This, he announced cheerfully, was one of the most striking neurological conditions there is to see: transient global amnesia. You might think his cheer out of place – after all, here is a man who has inexplicably lost 8 hours of his life – but considering that the other options were either an epileptic event or a TIA I think that his positivity rather appropriate. TGA has been shown to have little to no effect on people after an episode and has a very low chance of recurrence. Wonderful, he said, and arranged to send the man home to his family.
Later, I looked up this mystery diagnosis and it really is fascinating. TGA is exactly what it says it is – a temporary inability to lay down short term memory. Patients retain most of their faculties (including, alarmingly, the ability to drive), long term memories, and social behaviours – the only thing they can’t do is remember anything beyond the previous couple of minutes. As such, they are often unaware of where they are or when it is, but act exactly like a healthy person in all other respects. The uncanny thing is the repetition – it is said to be ‘like a tape player’ in that gestures, sentences and even tone are often exactly replicated over and over as they forget they’ve just done it. On questioning a patient can tell you their name, recognise close family members, and perform complex tasks. While they are often aware something is not quite right they can’t put their finger on it. Then it is gone with a little warning as it arrived.
Just as interesting is that nobody has a clue how it comes about. Theories range from a migraine-type cause to a focal epilepsy but nothing really holds up. TGAs appear suddenly, without warning, and vanish as abruptly as they arrive. 95% of people never have another, and there are normally no lasting effects.* People who have experienced an episode of TGA often relate it to water – baths, showers, or swimming in the cold. Other people link it to stress or emotional trauma. Even sex (or other ‘vigourous exercise’ has been known to set off a TGA. In our gentleman’s case, he had a few recent stressful elements in his life that could easily be partnered with his TGA. There is, of course, no way to know for sure.
There we have it, then. A peculiar, enigmatic happening that is come and gone in less than a day, leaving only an absent 8 hours in its wake. The memories may or may not return, but it is unlikely. One reassured patient, one more condition (hopefully) lodged in my memory, and one more day in the hospital draws to a close. Brains are amazing, don’t you think?
*there have been whispers of more sinister consequences, including a mild long-term cognitive deficit at one year and structural changes in the brain, but these are so far weakly supported.