ABSTRACT
Chronic daily headache (CDH) of long duration is a clinical syndrome defined by headaches that occur for four hours a day or more, on 15 days a month or more, over more than three months (1,2). CDH is one of the most common and disabling headache presentations in neurology centers; it afflicts 4% to 5% of the general population (3,4). Many patients with CDH are severely impaired (5). CDH sufferers usually have higher disability than those with episodic migraine (6).
