It is one of the nastiest pains there is. I sit absolutely still because any movement is agony and I pull my hair as hard as I can because the pain of that blocks the other a little. You want to sleep but you can't - and when you do you dream of pain."
Margaret Vinnell, who recently took early retirement from Holland Park primary school in Clacton, is describing a typical migraine attack. She suffered her first when she was only eight, but the condition didn't become a nuisance until she reached her 30s and was at its worst in her 40s. "I remember sitting in the classroom reading stories to the children with a waste bin next to me in case I was sick."
These days her attacks are less severe, thanks mainly to a new drug (one of the group known as triptans), the first that has worked for her. "If this type of treatment had been available 20 years ago, when I began full-time teaching, I might have been much more ambitious," she says wistfully. "I would have liked to see how far I could have gone and perhaps become a head. As it was, I was afraid to take on extra responsibilities because it's hard to be an effective team member when you're ill every three weeks."
In fact, Mrs Vinnell took few days off school because one of the ironies of migraine is that it tends to strike immediately after a period of activity - on Saturdays, or the first day of the holidays. "After a weekend attack I'd usually be well enough to go back to school on Monday, although I'd be working under par for several days. It is like being born defective," she explains. "But your misfortune doesn't show. You appear quite well, and for three-quarters of the time you are. Even doctors often don't always appreciate what is going on because when you're ill you can't go to the surgery and when you're well you don't want to."
About one in 10 of the population suffers from migraine, which affects three times as many women as men. Most women have their first attack in their teens, although it can begin in childhood and affects as many boys as girls up to the age of 11. Children's attacks, usually consisting of headache and vomiting, tend to be short and sharp, whereas in adults there is a build-up to the attack, which lasts from one to three days. It may strike once a week, once a month or just occasionally, and some sufferers remain free of attacks for months or even years.
Nothing annoys migraine sufferers more than the common assumption that it is "just a bad headache". American-born Daisy Thurbin, who teaches maths at Merton Further Education College, south London, recalls attacks so bad that "even though I am not at all suicidal, if I'd been able to get a gun, I'd have killed myself."
The excruciating pain is only part of it: "You also vomit and feel nauseous, and your memory and speech patterns are affected. You don't want anyone to speak to you or even walk across the floor and you can't tolerate noise or light. You become this horrible person, and no one is understanding because when you have a chronic illness the people around you lose interest in being sympathetic."
After years of consulting doctors and therapists on both sides of the Atlantic, she too has found respite in one of the triptan drugs - although these are available only on prescription and are unsuitable for many people. "Nowadays I don't have to miss work if I've caught an attack early enough. But I'm glad I teach adults because if I muddle my words up I can explain that I'm not drunk but have a migraine."
Dr Anne MacGregor, a specialist at the City of London Migraine Clinic, stresses that migraine sufferers are perfectly healthy when they are not having an attack. "We still don't know why people get migraines, although we can measure the alteration in body chemistry during one. Vessels in the head swell up, the stomach shuts down and it's like a total power cut.
"We see it as the body's response to a combination of circumstances such as lack of sleep, missed meals or overwork. But there are so many possible triggers - emotional, physical, dietary, environmental and hormonal - that identifying which ones are affecting an individual is a slow process. We ask patients to keep detailed three-month diaries of their lifestyles, food and stress levels, so we can look for patterns and tailor the treatment to the individual."
Dr MacGregor emphasises the importance of early remedial action. "Obviously teachers can't walk out of the classroom and lie down when they feel a migraine coming on," she says, "but they should have their pain-killers or prescribed pills with them and go briefly outside the door and take them immediately, before their stomach shuts down. Unfortunately, migraine is not taken seriously enough. As a result many people feel they have to hide it for fear of seeming inadequate."
Catriona Davies, a primary teacher in West Bromwich who suffers migraines once or twice a month, is certain they contributed to the breakdown of her marriage. "I was always ill when I was supposed to be relaxing and enjoying myself, and my husband thought it was just a nuisance. But now I live with someone who also suffers from migraine, I can appreciate how irritating it is."
If an attack starts when she is in school she takes her pills and carries on, "although the children often ask if I'm all right". If she has to take time off, she feels bad. "This is a supportive school, but just occasionally you get a comment like, 'Oh dear, not another headache. We're going to have to cut your head off one of these days', which is just what you need when you already feel desperately guilty."
To avoid this kind of problem, Sussex science teacher Alan James (a pseudonym) keeps his migraines a secret at work. "There is prejudice," he says, "and as most of my attacks occur on Saturdays or at the start of the holidays, there is no need for the school to know. I took only one day off with it last year. I can cope with the occasional attack at school as long as I have my pills with me. The only thing that can really impede my teaching is if I develop a blind spot and can't write on the board."
The two main support organisations, the Migraine Trust and Migraine Action Association, advise sufferers to work closely with their GPs to identify their particular triggers and find the most effective treatment. "The best approach to migraine is to treat the whole person," explains a trust spokesperson.
Many sufferers find yoga, meditation, relaxation techniques and complementary therapies such as acupuncture and reflexology helpful, and some swear by the herbal remedy feverfew.
"Feverfew does work for some," says Dr MacGregor. "But not enough research has been done on the long-term safety of herbal remedies."
Further information and advice is available from The Migraine Trust 45 Great Ormond Street, London WC1N 3HZ Tel: 0171 831 4818 The Migraine Action Association 178a High Road, Byfleet, West Byfleet, Surrey KT14 7ED. Tel: 01932 352468 The City of London Migraine Clinic 22 Charterhouse Square, London EC1 6DX Tel: 0171 251 3322
Migraine is more than just a headache. If you have two or more of the following symptoms during an attack, you are probably suffering from migraine
* Visual disturbances, including blind spots, distorted vision, flashing lights or zig-zag patterns
* nausea, vomiting or diarrhoea
* increased sensitivity to light, sounds or smells
* stiffness in the neck and shoulders
* tingling or stiffness in the limbs
* inability to concentrate
* difficulty in speaking