Introduction

Headache is one of the most common nuisances known to man. The pain may be secondary, as in fever or hypertension, or primary, as in migraine. It has been estimated that about 30% of people in the western world suffer from one or more severe headache episodes per year. In the UK, more than 3 million workdays are estimated lost per year due to headache. The majority of headache patients have migraine, tension-type headache (TTH) or combinations of these. About 65% of the patients seen in headache clinics suffer from migraine, 25% from TTH and about 10% from other types of headache. Although such samples are selective, the relative proportions of types of headache are probably representative of the population. The causes of headache syndromes like migraine, cluster headache and TTH are largely unknown. However, knowledge about clinical, physiological, biochemical and psychological characteristics is substantial.

The definitions of headache syndromes lacked precision in the past, making it problematic to compare studies. Therefore, the International Headache Society (IHS) formed a Classification Committee which published diagnostic criteria in 1988 (IHS, 1988). Most research published after 1988 adheres to these criteria.

Pathophysiology

In the field of psychophysiology, psychological variables are manipulated while physiological variables are measured as dependents. The field has yielded important information about the pathophysiology of headache. When reviewing the literature on response characteristics of patients, it becomes evident that the earlier distinction between migraine as vascular, and TTH as myalgic is oversimplified.