Chronic daily headache: old problems, new vistas

In 1998 the problems concerning chronic daily headache (CDH) were neglected by the classification of International Headache Society (IHS). More than ten years later, this issue is still debated, also in light of the foreseen revised classification. Several therms have been used to define the clinical picture of CDH, and different criteria have been proposed for the diagnosis of these forms. In most cases, CDH appears to evolve from an episodic migraine, but the temporal limits between an episodic and a no-longer episodic form of migraine are questionable