Migraine with and without aura: the same disease due to cerebral vasospasm of different intensity. A hypothesis based on CBF studies during migraine.

The CBF studies performed so far during attacks of migraine, may be interpreted as favouring "the vascular theory." This applies to migraine with aura as well as to migraine without aura. Migraine without aura may be due to mild focal CBF reduction--too mild to be detected by the available CBF techniques (i.e. 20% or less) and too mild to produce ischemia and aura phenomena. Migraine with aura may be due to focal CBF reduction severe enough to produce ischemia (i.e. 50% or more) and therefore also aura phenomena. The phenomenon termed "spreading oligemia" typically seen in CBF studies during migraine with aura, may be an artifact reflecting a gradual decrease of CBF in an area of constant size. The typical "march" of the aura symptoms may reflect differences in the ischemic threshold of various neurones leading to dysfunction of more and more neurones as the blood flow gradually decreases. It is concluded that migraine with and without aura may be due to the same disease process--the only difference being the intensity of vasospasm and CBF reduction.