Migraine triggers: practice and theory.

The basis of our belief in migraine triggering factors is questioned. To avoid creating migraine-mythology, it is proposed that a trigger for migraine must also cause headache in non-migrainous subjects. This headache-migraine parallelism is examined and if correct, casts doubt on migraine precipitation by cheese, chocolate or allergy. A further weakness of "dietary migraine" is pointed out because the quantity of the trigger consumed, or the time interval between ingestion and the onset of attacks, are rarely mentioned, let alone studied. A difficulty in assessing migraine precipitants is that two factors may act in unison, e.g. stress and not eating. Further an external factor may provoke an attack only if the migraine "milieu intériur" is set appropriately, for example the hormonal state in a woman's menstrual cycle. The value of studying migraine precipitants is two-fold: (1) it provides a means of counselling patients to avoid or reduce these factors, thereby diminishing frequency and severity of attacks; (2) a comprehensive migraine pathogenetic theory must incorporate how and where precipitants act. It is concluded that analysis of triggering mechanisms lends support to the concept that migraine is a primary neurological disturbance with secondary vascular manifestations.