Causes of Migraine

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The cause of migraine is unclear.

It is thought migraine may occur when there is a decrease then increase in blood flow to part of the brain, probably caused by blood vessels narrowing then opening again. The stretching of the blood vessel wall causes pain.

In addition to any blood vessel changes, it is thought that some chemicals in the brain increase in activity during a migraine. It seems that levels of serotonin, or 5HT (a chemical that is important to brain function and has an effect on the size of blood vessels) decrease at the onset of the headache but are normal in the periods of time between attacks.

If you get migraines, you may have a more sensitive pain centre in the brain than other people. This means that things like bright lights or when you are tired affect your pain centre more.

Triggers:

Most attacks occur for no apparent reason, but some people notice triggers including:

foods, such as dairy products (particularly cheese), chocolate, alcohol (particularly red wine), caffeine, citrus fruits, nuts, fried foods and foods containing monosodium glutamate (MSG) such as Chinese food, processed meats and frozen pizzas.
bright lights (photophobia),
insufficient food or missing meals,
long journeys/travelling,
certain medication such as sleeping tablets or hormone replacement therapy (HRT),
loud noises (phonophobia),
strong smells (osmophobia),
changes in the weather,
neck and back pain,
stress or anxiety, and
tiredness, not having enough sleep or oversleeping.

There can be more than one trigger for a migraine. Being tired, in combination with another trigger can set off a migraine. It may be useful to keep a diary of your symptoms so you can look for a pattern and avoid certain triggers. Note the date of the attack, what time of day the attack began, what the warning signs were, your symptoms (including the presence or absence of an aura), what medication you took and when the attack ended. It is worth noting that some things that you may think are triggers (for example, chocolate), may have been a craving in the prodromal phase. This means that the migraine was on its way before you ate the chocolate, so the chocolate was not the cause.

Hormones:

Migraine is more common in women than men, and this is linked to hormonal changes. During the menstrual cycle, the levels of oestrogen and prosgesterone in a womenâ€™s body fluctuate. Evidence shows that migraine is linked to a fall in oestrogen levels. Many women find that the worst headache coincides with the start of their period, which is when oestrogen levels are lowest. Many women find that their migraine headaches become less severe or disappear when they are pregnant.

The combined oral contraceptive pill, containing oestrogen and progesterone can make migraine worse. If you suffer from severe migraine that has neurological symptoms (â€˜classicalâ€™ migraine), you should not take the combined contraceptive pill. Neurological symptoms include speech and vision difficulties, and numbness or tingling affecting a limb or one side of the body. Taking oestrogen may increase your risk of having a stroke if you suffer from severe migraines.

If your first ever migraine occurs whilst taking the pill, you may have to stop taking it. If this happens, you should consult your GP who will assess the headache. If the migraine is not suggestive of any disturbance of blood flow to the brain, you may be able to continue with the combined pill.