Triggers of Primary Headaches: Issues and Pathways Forward

The triggers of primary headaches have considerable significance for our understanding and management of headache and migraine. Triggers explain the variance in headaches - why they occur when they do. Trigger management is generally viewed as an important component of a comprehensive treatment approach for headaches. Historically, however, triggers have not had a prominent place in the headache literature. This situation began to change 20 to 30 years ago, and the pace of change has increased exponentially in recent times. Nevertheless, the field is beset with issues that have held it back from achieving more. This review will focus on elaborating those issues with the goal of suggesting ways forward. The first issue considered will be the definition of a trigger, and how specific triggers are labeled. Consideration will then be given to a classification system for triggers. The review will discuss next the evidence relating to whether self-reported triggers can, indeed, precipitate headaches, and how the capacity to elicit headaches may be acquired or extinguished. Attention will be given to the very important clinical issue of trigger management. Finally, the pathways forward will be proposed. Perhaps the most useful thing to accomplish at this point in time would be agreement on a definition of headache triggers, a list of triggers, and a classification system for triggers. This would greatly assist in comparing research on triggers from different research groups as well as eliminating some of the issues identified in this review. An authoritative body such as the American Headache Society or the International Headache Society, could establish a multidisciplinary committee that would complete these tasks. Consideration should also be given to incorporating triggers into the International Classification of Headache Disorders as an axis or via the use of codes, as this would raise the profile of triggers in assessment and management.