Migraine, tension-type headache, and transformed migraine.

Migraine and tension-type headache (TTH) are highly prevalent primary headaches that remain underdiagnosed and undertreated in clinical practice. The similarities and differences between migraine and TTH may impose diagnostic challenges as well as management difficulties. In addition, the possibility of migraine chronification or transformation in daily or near-daily headache raises the potential level of interaction between pathophysiologic mechanisms of TTH and migraine. The continuum concept is a possible key to the understanding of this association. Future studies are necessary to clarify epidemiology, pathophysiology, and management of these two most prevalent headaches.