About a year ago, I had a really bad migraine that I just couldn't shift. I'd had migraines before but, over the course of two weeks, this one kept coming back.
As a neuroscientist, whose research has covered what happens to the brain during migraine, I was determined to get to the root of the problem. I tried all sorts: I had my eyes tested, and I even went to the dentist to make sure it wasn't something going on with my teeth and causing a headache.
Eventually, I identified the culprit: stripes. It turned out that around the time the migraine had started, my wife had bought lots of stripy tops, some with tightly-packed black and white lines, which she'd taken to wearing. (We'll come back to why this triggered the migraine later.)
It is estimated that six million people in the UK suffer migraines. It seems to affect one in five women and one in 15 men, according to the NHS. (The higher rate in women is most likely due to hormones involved in the menstrual cycle.)
A migraine is not 'just' a bad headache. And not every really painful headache is a migraine.
While headaches can have different underlying causes (such as dehydration or eye strain), fundamentally they are triggered when blood vessels in the brain get bigger (dilate). This process, called vasodilation, is to bring more blood quickly to areas of the brain it thinks are in need. This stretches the blood vessel walls beyond comfortable limits, setting off their pain receptors.
While this blood vessel dilation happens in migraine, too, it is only part of the process. Migraine is a whole-body experience involving a complex pattern of changes in the brain that means it can also involve nausea, vomiting, appetite changes, clumsiness, visual disturbances, sensitivity to light and fatigue.
Early warnings of a migraine
The first phase of a migraine is the 'prodrome' phase — a warning of what's to come. Here, there can be subtle behavioural changes which can occur a couple of hours or even days before the aura (a sensory disturbance that accompanies some migraines) and the pain of migraine starts properly.
You might yawn more, be less alert, have cravings or be hungrier than usual. Walking into shops with really bright lighting might unsettle you to the point of distraction.
Many sufferers are quite bad at spotting this stage. Recent work by Sanitaria Hospital in Madrid suggests that only a third of patients are good predictors, in that they could spot an impending migraine more than 50 per cent of the time.
It takes a certain amount of self-awareness to register this first stage, but it could help identify what your triggers for migraine are — some of which you'll be able to control, some of which you may not.
It could also help to make sure that medication to lessen the impact of an attack is taken at the earliest opportunity.
Why you may see flashing lights
After the prodrome stage, comes the aura — commonly, seeing flashes of light or blindspots in your vision. Most people report that these changes in perception come on gradually, last between five and 20 minutes, and are undetectable after an hour. (If you experience aura for the first time, it is worth talking to a doctor to rule out anything more serious, and certainly if the aura lasts for more than an hour).
In migraine, there is a wave of excitation across the brain, in which many nerve cells become active in a coordinated way.
It is thought that the 'light' of aura is created because the brain area that normally decodes signals from the retina (the light-sensitive layer at the back of the eye) is activated in this wave, too, so you end up detecting 'light' that isn't really there.
Alternatively, you might feel things that aren't really there, such as a tingling in your skin, or you might smell something, or hear dripping taps, or taste something that isn't there (particularly a metallic taste).
This is all down to the areas thought to be wrongly activated in the wave of excited nerve cells that takes over the brain during migraine. Some don't experience migraine aura at all; they go straight to the 'pain' phase.
It is not clear why some people experience aura and others don't. One theory is that while the same wave of activity is experienced, not all brains translate the brain cell activation into imagined sensation — something that has been labelled 'cortical ineloquence' by researchers.
WHY IT'S SO EXCRUCIATING
The ubiquitous throbbing pain that migraineurs describe is often centred in the forehead towards the temple.
This is thought to be due to a concept called referred pain, where the unpleasant sensation is felt at a site that's distant from the underlying cause — a result of the brain mixing up messages from various nerves all around the body that will converge at a single point.
It is the same principle that explains why pain down the left arm or jaw can be a sign of a heart attack, because the sensory nerves from your heart are bound up with the pathway from your arm and jaw.
In migraine, where you feel the pain depends on your anatomy.
So what kicks it off? After the wave of excitation (the surge of activity through the brain's nerve cells) comes a sudden depression, where your nerve cells effectively go to sleep.
Nerve cells activate through the movement of charged particles, such as sodium and potassium. Normally, nerve cells are really particular about what comes in and goes out; but the fast and furious wave of brain activity in migraine means everything ends up in the wrong place.
Too much potassium ends up trapped on the outside of the cell and sodium gets trapped on the inside, when it should be the opposite. This makes it impossible for the cells to pass on any signals at all — so everything stops. Then, the excess, out-of-place potassium acts directly on the tiny branches of the arteries in the area, restricting blood flow, and also activates pain receptors in the blood vessels.
Your brain then arranges a hefty inflammatory response to try to induce vasodilation to regulate blood flow again.
Although the nerves only 'sleep' for a few minutes, it then takes another 30 minutes for normal activity to be recovered.
And the excruciating pain triggered can take anything from four to 72 hours to ease.
THE TROUBLE WITH STRIPY TOPS …
But why do a migraineur's nerve cells go bananas in the first place? We have some tantalising evidence — and it lies in the visual cortex.
This is an area at the back of the brain that processes information from the eyes. In particular, people who experience migraine have a much more excitable area of the visual cortex known as V1.
If we just had V1 to process vision with, we would see the world as a collection of lines. This is because the millions of nerve cells here only fire in response to lines. (Other parts of the visual cortex, imaginatively called V2, V3, V4 and V5, are used to build up the picture, detect edges and movement and overall contrast.)
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