Chronic daily headache: transformational migraine, chronic migraine, and related disorders.

Chronic daily headache is an important category of headache illness that affects 4% of the general population. Within this classification are four chronic headache entities: chronic migraine/transformational migraine, chronic tension-type headache, hemicrania continua, and new daily persistent headache. Chronic migraine/transformational migraine is the most common of these entities and is frequently accompanied by medication overuse, neurobehavioral comorbidity, and disability. The terminology and classification of this entity continue to be confounding. Current research is directed at identifying factors that might promote the progression of this disorder from episodic migraine to daily or almost daily headache, and at identifying the best approaches to treatment, which include both pharmacotherapeutic and non-medicinal interventions. Patients with intractable cases are often hospitalized as a consequence of the convergence of several factors that make outpatient management unlikely to succeed.