[Chronic daily headache--history, epidemiology, clinic and future].

Chronic daily headache (CDH) is not a diagnosis but a category that contains many disorders representing primary and secondary headaches. CDH is defined as headaches which occur more often than 15 days per month for at least 3 months. Approximately 3 to 5 percent of the population worldwide has daily or near-daily headaches. Primary CDH of long duration includes transformed migraine, chronic tension-type headache, new daily persistent headache, and hemicrania continua. Transformed migraine and medication-overuse headaches are among the most common and challenging of the CDH disorders. Treatment of CDH focuses on reduction of headache triggers and use of preventive medications such as antidepressants, antiepileptic drugs and beta-blockers. Antidepressants are the most common preventive medications for all types of CDH, which suggests that central serotoninergic neurotransmission can be an important factor in the pathophysiology of chronic pain syndromes.