The challenge of new daily persistent headache.

New daily persistent headache is a rare chronic daily headache of long duration characterized by the abrupt onset of persistent headache that generally develops over less than 3 days and does not remit. While it was initially thought to be a benign, self-limiting disorder, further research has shown that a significant percentage of patients continue to suffer for many years, often experiencing pain that is refractory to treatment. This article reviews the symptoms, pathophysiology, diagnostic criteria, diagnostic testing, treatment, and prognosis.