What causes it?

The exact cause of migraine is not known but there is a strong hereditary factor with more than half of sufferers having a family history of the condition. It was thought to be due to an increase in blood flow in the arteries of the scalp and brain but recent studies using modern imaging techniques have cast doubt on this theory. Changes in cerebral blood flow do occur in an attack of migraine but whether these are the cause or effect of the condition remains unclear. However, its response to treatment with drugs that affect cerebral circulation suggests an underlying vascular cause.

Several trigger factors that induce an attack are recognised. Cyclical oestrogen production associated with the menstrual cycle is a significant trigger and probably explains the much greater incidence in women and the change in prevalence at puberty. Attacks are more frequent and difficult to manage in the pre-menstrual period and oestrogen-based oral contraceptives and hormone replacement therapy can exacerbate the problem.

Other trigger factors may be loss of sleep, loud noise, changes in the weather, travel and lack of food. Certain foods such as cheese and chocolate as well as food additives, alcohol and caffeine can also precipitate an attack in susceptible individuals.