Platelet monoamine oxidase activity and headache.

Mean platelet monoamine oxidase activity was reduced compared with control values in groups of headache-free male (but not female) patients suffering from classical migraine and from tension headache. Mean activity in male cluster patients, headache free, both during acute and quiescent phases of their illness, was also notably reduced. Retesting some migraine subjects after up to four years, showed that low activity may be a persistent feature: the correlation coefficient for repeated assays was 0.91 (p less than 0.01). There was no relationship between platelet monoamine oxidase activity and history of dietary migraine. A subgroup of headache patients with permanently low monoamine oxidase activity values may have been defined.