Information in this section pertains to all global PEN® partners except where country flags are
visible. Click on the flag(s) for country-specific information. If a country flag is not listed, there is
no information specific to that country.
Disease Etiology
The etiology of migraine headache is not completely understood. The vascular theory, proposed in the 1940-1950s, theorized that auras were caused by vasoconstriction and that rebound vasodilation caused the pain of migraine headaches (1). However, this theory has been discounted and replaced by the neurovascular theory. According to the neurovascular theory, migraine is “primarily a neurogenic process with secondary changes in cerebral perfusion” (2). Central to the