Is chronic migraine a primary or a secondary condition?

In the light of the pathophysiologic knowledge acquired in recent years, a tentative redefinition of some types of headache, until now defined as primary, is now possible. Chronic migraine is proposed here as the consequence of "processes" to be ascribed to mechanisms activated by comorbid conditions. The observations supporting the possibility that allodynia represents the process leading to pain progression, which occurs in some migraineurs, are discussed.