The family had moved to Aberdeenshire, and she took her son to a GP there.The doctor suggested that he was suffering from migraine, the tummy aches being "abdominal migraine". Thomas was referred to the Royal Aberdeen Children's Hospital. There, the Grants struck lucky because they saw a consultant who had long been interested in childhood migraine.
Dr George Russell, a paediatrician and a reader in child health at Aberdeen University, was pioneering a "breakfast at bedtime"treatment - taking a starchy snack, such as a breakfast cereal, just before bed - which has helped hundreds of children and is now recommended by other specialists.
"We noticed that quite a lot of children brought to the clinic were waking up in the morning with headaches, especially those with abdominal migraine," Dr Russell says. "They also frequently had migraines at weekends, when they got up later. We decided it could be due to the blood sugar level falling too low. Some children have supper at about 5.30pm or 6pm and then do not eat anything until they wake up at about7am, which is a long time to go without food.
"So we suggested to parents that they give their child a starchy breakfast cereal just before putting them to bed, at say 8.30pm or 9pm, to see if that helped. In eight out of 10 cases, we found that it did. A starchy cereal is digested quite slowly, so that it provides a night-long drip- feed of sugar."
Mrs Grant started giving her son Weetabix just before bed, at 9pm, and found a huge difference. "He has been much, much better since then," she says. "He occasionally still gets a headache, but just a mild one, and he is never laid low with it." Thomas is also pleased. "It felt really, really bad before. Now I sometimes get a headache but it goes away quickly."
One of the hurdles the Grants initially faced was the belief that children do not get migraine. In fact, at least 250,000 children suffer from the condition (characterised by recurrent bouts of headache with nausea and vomiting) and the incidence could be far higher. A study of 2,000 schoolchildren in Aberdeen showed 10 per cent were affected, missing twice as many school days as other children. Before puberty the disorder affects both sexes equally, but adolescent girls suffer more commonly than boys.
The other problem for families such as the Grants is the failure to recognise abdominal migraine, which was identified 100 years ago and whose symptoms include recurring abdominal pain, nausea, pallor, fever, dizziness and limb pains. A recent study in Birmingham showed that about 1 per cent of schoolchildren suffer from abdominal migraine, the condition peaking between the ages of five and seven.
Dr Russell emphasises that his breakfast treatment does not work in all cases, because lack of food is not always the culprit. "It is a mistake to look for a single trigger in migraine, because there are many," he says. "But a late evening snack is certainly worth trying in children who wake up with a headache."
For other children, there are other solutions. Dr Anne MacGregor, a registrar at the City of London Migraine Clinic, has three rules: identify and avoid triggers, treat symptoms early and keep the treatment simple.
Triggers can include lack of food and sleep, exercise, excitement, stress, bright lights and loud noises. Resting, reducing all stimuli, shutting curtains, minimising noise, and applying hot and cold compresses to the head can help.
"Unfortunately parents often do not recognise their child's problem as migraine and, even where they do, they do not always consult a doctor, in the mistaken belief that nothing can be done for it," she says. "When drug treatment is needed, the least toxic drugs should be given. In practice, this means paracetamol tablets or syrup."
One child whose migraine has been helped by early intervention is Christopher Murty,12, from Dunblane, Scotland. His GP suggested that his problem might be hypoglycaemia (low blood sugar), because the attacks often came on just after football or running.
Christopher's problem got so bad that on several occasions, including once last summer, when he was standing in a Boys Brigade parade, he fainted. His mother, Margaret Murty, finally took him to a migraine specialist, Dr Ishaq Abu-Arefeh, then at Stirling Royal Infirmary, who diagnosed migraine and recommended early treatment. "Now, as soon as he feels an attack starting, he takes paracetamol and goes to bed," she says. "That seems to work for him. It has helped a lot. It was a relief just knowing what was wrong." Christopher adds: "It was a horrid feeling. I felt dizzy and then I knew that I would feel sick, and have a headache and a stabbing pain in my right eye. The attacks have been as frequent since I saw the doctor, but not as bad, because I act more quickly."
Dr Abu-Arefeh has established a headache clinic for children at the Royal Hospital for Sick Children in Glasgow, and thinks the unit is probably the first of its type in Europe. He believes it will be useful for research and would like to discover whether the mechanisms and physiology of childhood migraine is the same as for adult migraine, and to investigate the genetic basis.
"The breakthrough has not yet arrived and most of the research is scratching at the surface," he says. "But there are many ways in which you can help patients. If they know what to do when they get an attack, that is a great improvement".