Increased brain serotonin synthesis in migraine

Objective: To measure brain serotonin synthesis with PET using the tracer alpha-[C-11] methyl-L-tryptophan in migraine patients. Background: Although the cause of migraine remains poorly understood, there is considerable evidence to support a role of the neurotransmitter serotonin in the pathophysiology of migraine. Methods: We studied 11 women (aged 33 +/- 7.7 years) with a diagnosis of migraine according to International Headache Society criteria and 8 healthy women (aged 29 +/- 9.2 years). Five patients were studied before and after chronic treatment with propranolol or nadolol. Results: Serotonin synthesis capacity (K-complex) values in migraine patients were higher than those measured in controls throughout the brain (p = 0.016); mean K-complex for whole brain was 0.0077 +/- 0.0020 mL/g/min in patients with migraine and 0.0054 +/- 0.0003 mL/g/min in controls. The regional pattern did not differ between the two groups. However, the K-complex for whole brain in the subgroup of migraine patients with aura (n = 3) did not differ from that of the control group (p = 0.32). In the five patients studied twice (before and after treatment), we found a trend of increased whole-brain K-complex after drug treatment (p = 0.06). Conclusions: Our findings indicating increased brain serotonin synthesis capacity in migraine patients are consistent with previous reports of systemic alteration of serotonin metabolism in patients without aura. Our results also suggest that the mechanism of action of beta-adrenergic antagonists for migraine prophylaxis may involve regulation of serotonin synthesis.