Chronic Daily Headache: Theory to Therapy.

Headaches are among the most frequent symptoms for which Americans seek physician advice and treatment. Although headache may herald a serious underlying organic or psychological illness, it more commonly represents a primary disorder of brain stem nociceptive processing and modulation. Chronic daily headache characteristically develops gradually from episodic tension or migraine-type headaches into a refractory syndrome often associated with medication overuse and disability. Better understanding of the pathophysiology and evolutionary mechanisms involved in the development of chronic headache has led to recommended changes in nosology originally proposed by the International Headache Society (IHS). Recent scientific and clinical observations prompting revised classification have also led to the integration of pathoanatomic models, which explain persistent headache. Strategies for the management of chronic craniofacial pain should emphasize key behavioral and attitudinal changes and avoidance of medication overusage.