Allodynia in migraine: association with comorbid pain conditions.

Background: Cutaneous allodynia (CA) in migraine is a clinical manifestation of central nervous system sensitization. Several chronic pain syndromes and mood disorders are comorbid with migraine. In this study we examine the relationship of migraine-associated CA with these comorbid conditions. We also evaluate the association of CA with factors such as demographic profiles, migraine characteristics, and smoking status that may have an influence on the relationships of CA to pain and mood.

Methods: Data are from a cross-sectional multicenter study of comorbid conditions in persons seeking treatment in headache clinics. Diagnosis of migraine was determined by a physician based on the International Classification of Headache Disorders-II criteria. Participants completed a self-administered questionnaire ascertaining sociodemographics, migraine-associated allodynia, physician-diagnosed comorbid medical and psychiatric disorders, headache-related disability, current depression, and anxiety.

Results: A total of 1413 migraineurs (mean age = 42 years, 89% women) from 11 different headache treatment centers completed a survey on the prevalence of comorbid conditions. Aura was reported by 38% and chronic headache by 35% of the participants. Sixty percent of the study population reported at least one migraine-related allodynic symptom, 10% reported > or =4 symptoms. Symptoms of CA were associated with female gender, body mass index, current smoking, presence of aura, chronic headaches, transformed headaches, severe headache-related disability, and duration of migraine illness from onset. The prevalence of self-reported physician diagnosis of comorbid pain conditions (irritable bowel syndrome, chronic fatigue syndrome, fibromyalgia) and psychiatric conditions (current depression and anxiety) was also associated with symptoms of CA. Adjusted ordinal regression indicated a significant association between number of pain conditions and severity of CA (based on symptom count). Adjusting for sociodemographics, migraine characteristics, and current depression and anxiety, the likelihood of reporting symptoms of severe allodynia was much higher in those with 3 or more pain conditions (odds ratio = 3.03, 95% confidence interval: 1.78-5.17), and 2 pain conditions (odds ratio = 2.67, 95% confidence interval: 1.78-4.01) when compared with those with no comorbid pain condition.

Conclusion: Symptoms of CA in migraine were associated with current anxiety, depression, and several chronic pain conditions. A graded relationship was observed between number of allodynic symptoms and the number of pain conditions, even after adjusting for confounding factors. This study also presents the novel association of CA symptoms with younger age of migraine onset, and with cigarette smoking, in addition to confirming several previously reported findings.