Why are we asking this now?
New research has shed light on why migraine sufferers are often sensitive to light. Specialised nerve cells in the eye appear to trigger migraine headaches even in people who are registered blind.
Scientists identified specialised, light-sensitive cells in the retina of the eye. They are involved in sending signals to the brain via the optic nerve and appear to be involved in "photophobia", when people react badly to light. Although still at an early stage, it is hoped that the research into these light-sensitive cells, called melanopsin photoreceptors, may lead to new ways of treating migraine attacks.
What is migraine?
It is more than just a splitting headache. A migraine attack involves a pulsing or throbbing pain in an area of the head, often on one side but not always the same side, and can be accompanied by extreme sensitivity to light, nausea and vomiting. The attacks can last for between four and 24 hours, although 72-hour attacks are not unknown. They are extremely debilitating. Normal, over-the-counter painkillers may not always be effective, especially if they are taken when the migraine attack has already started.
Classic migraine, now known as migraine with aura, involves some kind of visual disturbance, such as flashing lights, blind spots, tunnel vision, zig-zag lines or even temporary blindness. Common migraine, or migraine without aura, does not involve visual disturbances but often results in photophobia and increased sensitivity to noise, sounds and even smells.
Is migraine common?
It is thought that everyone has the capacity to suffer from migraine but in practice between 10 and 15 per cent of people have increased susceptibility – about 8 million sufferers in Britain. Migraine is about three or four times more common in women than in men. It affects all social classes and can strike children as well as adults, although attacks appear to become less frequent as a sufferer gets older.
Migraine attacks cost the UK economy between £1bn and £3.5bn a year, mostly in lost work, with 190,000 people a day suffering a debilitating attack. The World Health Organisation has classified migraine headache as a major health disorder and has rated migraine as one of the 20 most disabling lifetime conditions.
The frequency of attacks varies greatly from person to person, and from one time of a person's life to another. On average, people experience about 13 attacks per year, but in some cases people can suffer from three or four attacks a week, while other people may have just one or two a year.
What causes migraine?
There is no simple explanation for why someone suffers from migraine because the exact causes are not understood. However, scientists believe that migraine is influenced by changes in the level of serotonin (also known as 5-HT), a neurotransmitter in the brain. When these levels change, it results in an inflammation that causes blood vessels in the brain to swell and press on nearby nerves, causing pain. More precisely, migraine is believed to be due to expansion of the cranial blood vessels and the release of pro-inflammatory neuropeptides through nerve endings in the trigeminal nerve system, the nerve responsible for sensation in the face. The involvement of the trigeminal nerve may explain why many migraine sufferers become sensitive to anything touching the face or head: shaving or combing the hair can be painful and unpleasant.
What triggers migraine?
Many things appear to trigger a migraine attack, and they can vary from person to person. The sort of things that people have reported as triggers for migraine include: sleep (either too much or too little), skipped meals, bright lights, strong smells, noises, hormone changes due to the menstrual cycle, stress and anxiety, weather changes, alcohol (particularly red wine), caffeine (either too much or none at all), certain kinds of food (cheese, hot dogs or chocolate) and even artificial sweeteners.
Of all these many kinds of triggers, those that appear to be the underlying factors for many migraine sufferers are low blood sugar due to irregular eating, erratic sleeping patterns, dehydration, stress and hormonal changes linked with the menstrual cycle.
Can migraine be treated?
There are two forms of treatment. The first is to try to prevent an attack by prophylaxis, often using medicines designed for other conditions, for example using antidepressants such as amitiptyline and venlafacine or beta-blockers such as propranolol and timolol. These are taken on a long-term, daily basis to minimise the risk of an attack.
The second form of treatment is to take drugs designed to relieve the pain. Some over-the-counter painkillers can work if taken early enough, but many migraine sufferers needed something different or stronger and there is a danger of "rebound" headaches if painkillers are taken too often.
Two classes of prescription drugs are commonly used to treat migraine attacks: the triptans (such as zolmitriptan and sumatriptan), which work by trying to balance levels of serotonin in the brain, and the ergot derivatives, which work in a similar way to the triptans but can have quite serious side effects.
The antimigraine activity of the triptans is probably due to them acting in a similar way to serotonin on the 5-HT receptors in the intracranial blood vessels and nerves of the trigeminal system, which result in cranial vessel constriction and inhibition of the release of pro-inflammatory neuropeptides. Like all anti-migraine drugs, however, the triptans have to be taken early on in an attack. The longer a patient waits, the greater the chances of the drug failing to relieve the symptoms.
Is there anything else a migraineur can do?
Charities such as Migraine Action ( www.migraine.org.uk) and Migraine Trust ( www.migrainetrust.org) recommend that people keep detailed diaries for a few months to document their attacks. This helps to identify the sort of factors that may act as a trigger, which can then be used to avoid further attacks. Managing lifestyle is seen as an effective way of preventing or limiting the number of attacks.
In addition, there are other simple measures that can have an impact. Going to bed and getting up at regular times, and keeping to regular, healthy meals both appear to help many sufferers. Regular exercise, drinking water and cutting down on alcohol and caffeine in coffee and tea can also help. Reducing or managing stress can also prevent migraine attacks. Some people also report benefits from regular acupuncture sessions.
Where do we go from here?
Migraine experts such as Andy Dowson, director of headache services at King's College London, believe that the latest study on photo-sensitive cells in the eye may provide a concrete target for developing new kinds of migraine drugs. Since the triptans were developed some 20 years ago, there has been something of a hiatus in drug development, but the new research gives hope that eventually science will come up with some better treatments for this debilitating condition.
Will new treatments prove more successful at combating migraine?
*Identifying how light-sensitive cells in the brain cause migraine can help better target cures
*Painkillers used in the past can have serious side effects, of which new drugs could steer clear
*Recent research shows how migraine can be caused by a variety of factors, rather than one specifically
*Development of new drugs has been disappointing since the advent of triptans 20 years ago
*The most effective cures may still be simple lifestyle changes rather than different drugs
*Recent breakthroughs are welcome, but scientists are yet to harness them into sophisticated treatment