Platelet aggregation of migraineurs during and between attacks.

Platelet aggregation induced by ADP, collagen and platelet-activating factor was studied in common (migraine without aura) and classical migraine (migraine with aura) patients during and between attacks. The EC50* values for ADP and platelet-activating factor were significantly higher, whilst that for collagen was significantly lower in classical migraine patients during headache-free intervals compared to healthy volunteers. The EC50 values obtained for common migraine sufferers during symptom-free periods were similar to those of controls. During attacks, the EC50 value for ADP, but not for collagen and platelet-activating factor, was significantly higher than that of the controls. In healthy subjects a positive correlation was found between ADP and collagen-induced aggregation. In contrast, there was a U-shaped correlation matrix in classical migraine patients. The present observations show that platelet aggregation is altered in migraine patients and this raises the possibility that platelet-activating factor may be involved in the pathogenesis of migraine.