A redefinition of primary headache: chronic migraine

In the field of so-called chronic daily headache, it is not easy for migraine that worsens progressively until it becomes daily or almost daily to find a precise and universally recognized place within the current international headache classification systems. A proposal is advanced to differentiate between a form of high-frequency migraine without aura (10–20 days of headache per month for at least 3 months), to be considered as a migraine without aura subtype, and a form of transformed migraine (TM), to be considered as a complication of migraine. TM—a name that should be preferred to chronic migraine (CM)—would then replace the latter, from which it would distinguish itself by the more restrictive diagnostic criteria (at least 20 days of headache per month for at least 1 year, with no more than 5 consecutive days free of symptoms; same clinical features of migraine without aura for at least 10 of those 20 days).