Is the migrainous female brain different? Some new evidence

Abstract

Migraine is a very widespread and debilitating disease and, according to the World Health Organization, one of the most common disorders of the nervous system. It is twice as common in females as in males (Le et al ., 2011), and much more prevalent in females over the age of 12 years (Lipton et al ., 2001). In fact, the picture of migraine differs by sex before and after puberty. Under the age of 12 years, boys have a slightly higher incidence of migraine. Thereafter, prevalence increases for both sexes, peaking between ages 35 and 45 years, with an increase in the female-to-male ratio from 2:1 at the age of 20 years to 3.3:1 at the age of 40 years (Lipton et al ., 2001). This higher prevalence in females than males is common in many other chronic pain conditions, although the mechanisms underlying this difference are still poorly understood. Indeed, current knowledge of migraine pathogenesis is based primarily on experimental studies conducted in male animals, and lack of migraine research in female animals limits the clinical relevance given the sex bias in humans. The disproportionate number of females of reproductive age with migraine suggests that hormonal factors may play a role, but the complex pathophysiology indicates that additional factors are likely to be involved. It is now well recognized that: (i) at puberty females begin to demonstrate an increase in migraine prevalence compared to males; (ii) >55% of females have menstrual-related migraine; and (iii) the majority of females show improvement in migraine frequency and/or severity with pregnancy and at the menopause. More recently, migraine research has begun to help expand our understanding of the mechanisms underlying these differences, and how they can impact on treatment choices. Several hypotheses have been proposed to explain these differences in migraine and other …