Last weekend my wife Clare and I went to stay with my older brother John, who lives by the coast in Cornwall.
The weather was terrible. But, as readers of my regular Mail on Sunday column may remember, I enjoy swimming in the sea as often as possible, not least because of the health benefits. And so – despite it being cold and also raining – Clare and I decided we’d go for a dip in the ocean.
We’re well used to it, but after swimming around for a few minutes, we reckoned it was too chilly even for us – and challenged each other to a race back to the shore. I remember thinking: ‘I am definitely going to be able to beat Clare to the land.’ And then it all went blank.
Dr Michael Mosley, pictured in the sea, blacked out while swimming in Cornwall last weekend, leading his GP wife Clare to fear that he had suffered a stroke. The Mail on Sunday columnist was rushed to A&E in Truro
The next thing I remember is being in A&E at hospital in Truro, with Clare sitting beside me looking extremely concerned.
As we waited to be seen, she told me that after I emerged from the water, I looked perplexed.
I was not particularly distressed and in many ways appeared to be completely normal.
I was able to talk but apparently I kept asking her the same two questions over and over again: ‘Is it 2017?’ and ‘Did I pass out?’
I also kept reminding myself, out loud, that I had four children, and saying their names, as though I was frightened I would otherwise forget them.
For obvious reasons, this alarmed her.
With my brother’s help, Clare had got me dressed and drove me straight to hospital.
It was in the A&E department about two hours after the swim that my memory started to slowly come back and I became aware of my surroundings.
Clare, who is a GP, was obviously very worried that I might have had a mini-stroke – what is known as a transient ischaemic attack, or TIA.
This is when the blood flow is temporarily cut off to an area of the brain – usually the result of a blood clot that has formed elsewhere in the body and travelled to the neck, causing a blockage.
The disruption results in a lack of oxygen to the brain and this can lead to sudden symptoms that are similar to a stroke, such as problems with speech and vision, and numbness or weakness in the face, arms and legs.
A TIA doesn’t last as long as a stroke and its effects can often last only a few minutes or hours and fully resolve themselves within 24 hours.
But it’s a warning shot: a TIA means you are at high risk of a full-blown stroke. Strangely enough, I wasn’t that worried.
In fact, as we sat there, I told Clare my main concern was that going into hospital in the early weeks of August wasn’t a great idea, as this is when junior doctors start their new jobs.
When I was at medical school, we called it ‘the killing season’ – and studies have since shown, statistically, that patients may be slightly more likely to die if they are admitted to hospital in the first week of August than in the weeks before.
The fact that I could remember something I’d learnt at medical school was, I suppose, a reassuring sign.
After a full examination at the hospital, it was determined that Dr Mosley had experienced transient global amnesia caused by cold-water swimming
Fortunately, I was soon seen by a young doctor who clearly knew what she was doing.
She did a full neurological examination, which consists of testing things such as co-ordination and grip strength.
I didn’t have any obvious signs of physical or facial weakness, nor was my speech slurred – both telltale signs of a TIA and a stroke.
By this point I was lucid and the only thing that was obviously wrong with me was the fact that I had no memory of how I’d got there, or what had happened to me.
Puzzled, the junior doctor went off to fetch a more senior colleague. He did a further examination and gave me the good news that whatever was wrong with me, I had not had a stroke or epileptic attack.
Instead he said that I had almost certainly experienced something called transient global amnesia, and that it was brought on by cold-water swimming.
He said it was like a migraine attack, and although my memory had been badly affected, he fully expected it to return to normal within 24 hours.
Know the triggers – HEAT, COLD AND SEX
Back in the car on our way home, as anyone would, I immediately started to Google my new diagnosis. As the consultant had explained, although it is very scary, global (meaning total) transient (meaning that it passes) amnesia (the medical term for total or partial memory loss) also appears to be entirely benign.
It is rare – affecting about one in 10,000 people in the UK every year – and it typically happens to people over the age of 50.
The average age that someone has an attack is 62, I discovered, which happens to be my age.
People who experience this kind of memory loss don’t normally have high blood pressure or high cholesterol – both of which are major risk factors for strokes. Nor is the condition linked to a head injury, which could trigger epilepsy. In fact, the only thing it is associated with is a history of migraine attacks, which I have sometimes suffered.
The most common triggers of transient global amnesia are cold-water swimming, vigorous exercise, sexual intercourse or being under extreme stress.
Later I asked Dr Paul Jarman, a consultant neurologist at the National Hospital for Neurology and Neurosurgery, London: why?
He told me patients have actually been filmed in a brain scanner during such an episode.
So doctors know it’s due to a swelling in the area of the brain responsible for short-term memory, the hippocampus.
And this swelling can be caused by a certain type of breathing – known as valsalva maneuver, essentially holding your breath while trying to forcefully exhale (hence the association with swimming in very cold water).
‘This kind of strain rapidly increases the blood pressure in the chest, which can force the circulation to momentarily move in the wrong direction, up through the veins in the neck,’ he explained, ‘leading to a swelling of the blood vessels in the hippocampus.’
This swelling causes the short-term memory to be lost.
Dr Jarman said: ‘You retain no information. Patients will ask, the same questions over and over. You can tell them the answer but they will instantly forget.
‘As the blood flow returns to normal over a few hours, the hippocampus begins to function again. But no matter how hard you try, you’ll never recall what happened during that time because your brain simply didn’t store any information.’
The reason older people are more likely to be affected is because the tiny valves in the veins that usually stop blood flowing the wrong way weaken.
But patients who suffer transient global amnesia are no more likely to suffer a TIA or stroke.
As well as being benign, the other good thing about transient global amnesia is that once you have had one attack, you are extremely unlikely to have another. You are safe to drive and get on with your life. The symptoms of transient global amnesia include:
- Sudden short-term memory loss – which led to my repeating of a limited set of questions over and over. There may be some long-term memory loss – I wasn’t sure what year it was. Clare says she told me I was in Cornwall but I’d then forget and asked her where we were.
- You retain your sense of personal identity; you know who you are – Clare tells me I didn’t seem agitated at all, and knew who she was, and who I was. And I remembered the names of our children. I also kept asking whether I still worked in television – which I do – just to confirm I was right in thinking so.
- You can recognise and name familiar objects, and follow simple directions. While being examined in hospital, I was able to carry out simple tests of balance and co-ordination such as walking in a straight line and picking up objects. I was, I’m told, able to understand everything that was said to me.
- There are no signs of brain damage, such as weakness, paralysis, involuntary movement or inability to form and recognise words. This is why I wasn’t given a brain scan, as I had no other symptoms to indicate a stroke or TIA.
- You make a full recovery within 24 hours.
My memory didn’t suddenly come back, but over the hours in hospital Clare says I started to fill in the gaps.
I gradually remembered where the children all lived, for instance. And apparently I looked in a mirror and joked that I was glad I wasn’t actually 20 years older than I thought I was.
‘It was like all the filing cabinets of your memory were temporarily locked, and one by one, file by file, you found a way to access them again,’ Clare told me.
By the time I had got back to my brother’s house, I was able to remember just about everything.
I went to bed, slept for a good eight hours and woke up feeling absolutely fine.
As far as I can tell there have been no lasting effects.
Memory loss can be a warning shot
As I mentioned, one of the things that really worried Clare was that I might have had a mini-stroke or TIA. This happens when the blood flow to part of your brain is cut off by either a blood clot or a bleed. It requires urgent action.
About 46,000 Britons have a TIA each year, and all too often, because it passes and people get better, these episodes are ignored.
A recent Stroke Association survey revealed that two-thirds of people were unaware of the symptoms of a TIA.
Nearly three-quarters of respondents said that if they experienced these things, they wouldn’t take emergency action and go to hospital.
The BBC journalist Andrew Marr is a tragic example of what can happen if you have a TIA and ignore it.
Back in 2013 he was filming a documentary in Greece when, one day, he found he simply couldn’t deliver his lines while talking to camera.
He also felt really tired, so he stopped filming and went off to have a siesta. After a brief snooze he felt fine, so he decided it was nothing serious.
A few weeks later, when he was back home, he blacked out. He was alone at the time, so no one saw what actually happened. He swiftly recovered, and again, he decided to do nothing about it.
Then a few months later, despite being a very fit 53-year-old, he had a serious stroke while exercising on his rowing machine, from which he has never fully recovered.
A series of brain scans revealed that Andrew had had a couple of mini-strokes weeks beforehand – probably during those strange episodes – which were not investigated.
And it was these that had led to the full-blown stroke (not, as he’d initially worried, the vigorous workout).
According to the NHS, up to 80 per cent of strokes could be prevented following a TIA if the correct tests and treatments are carried out.
You can also reduce your risk of having a stroke by having your blood pressure, blood sugars and blood cholesterol checked on a regular basis.
One other thing you need to be aware of if you see someone having a funny turn is that they might be having an epileptic attack.
Although a severe attack, known as a grand mal, is often a dramatic and serious event, some people also have episodes of what is known as a petit mal, where they just appear to be absent, often staring off into space. These normally last for a few seconds. If this happens to someone you know or come across, and it doesn’t pass in a few minutes, you should keep them safe and ring for an ambulance.
It goes without saying, I’m glad that my amnesia wasn’t anything more serious.
And, despite this experience, I’m not put off going for cold-water swims in the future.
But I will make sure that when I do, I always have someone with me.
