Two years ago, 63-year-old Paul Bolding was on holiday in Croatia, visiting a beach on a tiny island with his wife, Kirsty. They decided to go to snorkelling, taking turns to go in the sea while the other one looked after their stuff. Paul had a swim and then dozed on a beach mat on the pebbles for a while. When he woke up he had no idea where he was or how he got there.
Not surprisingly, Paul was very scared. His wife took him to sit in the shade, desperately trying to find a way to calm him down and to work out what was happening to him. She told me in Radio 4’s All in the Mind that she soon worked out that he wasn’t able to form any new memories because he kept asking the same questions: “Do you think I’ve got sunstroke? Do you think I fell asleep in the Sun?” This happened more than 20 times.
Kirsty wondered whether this be the start of dementia. Fearing she might have to spend the rest of life looking after him, she drove him back to the town where they were staying, hoping that more familiar surroundings might trigger his memory. She had to order lunch for him because he didn’t know what to have. He couldn’t remember any of the previous 10 days of their holiday, even though part of it had involved meeting some relatives for the very first time.
By late afternoon he began to feel better, suggesting going for the walk they had discussed the previous day, suggesting his memory was returning. Within an hour everything had gone back to normal – everything apart from his missing memory of those six hours, which, to this day, has never come back.
Back home in the UK he visited his doctor, who told him he’d had an episode of transient global amnesia, a condition that’s more common in people over the age of 50 (which Paul was). Accident and emergency units are accustomed to seeing two or three cases a month.
During an episode, people still know how to drive and how to talk, but in a typical case such as Paul’s they can’t remember what they’ve been doing in the preceding days. Repeated questioning of others, just as Paul did on the beach, is a hallmark of this diagnosis.
The cause is still something of a mystery. Initially doctors thought these attacks might be a symptom of epilepsy or a migraine, or even a mini-stroke. But now they are considered to be unrelated to other health issues. The seahorse-shaped hippocampus, which processes our autobiographical memories, allowing us to store them long-term, is thought to hold the key.
Adam Zeman, professor of cognitive and behavioural neurology at University of Exeter Medical School explains how it works: “What we think happens is that the hippocampi get switched off temporarily. Paul’s case is classic. You lose memory of the past couple of weeks and can’t make new memories while the episode goes on.”
Brain imaging studies support this theory, revealing temporary abnormalities in the hippocampus during an episode.
Reviewing 142 individual women with transient global amnesia, doctors in France found that these cases were precipitated by stressful emotional events such as an argument, while in men they happened more frequently after physical exertion or immersion in cold water. People with a history of headaches were more likely to experience them.