Proposed new diagnostic criteria for chronic migraine

Introduction: ICHD-3 criteria for chronic migraine (CM) include a mixture of migraine and tension-type-like headaches and do not account for patients who have a high frequency of migraine but no other headaches. Materials and methods: Patients from the Danish Headache Center and their relatives with ICHD-3 defined CM were compared with patients with high frequency episodic migraine (HFEM). Danish registries were used to compare the socioeconomic impact in these two groups. A Russian student population was used to determine the generalizability of the number of patients fulfilling CM and the proposed diagnostic criteria for CM. Results: There was no difference in the demographic profile between the two groups in the Danish cohort. The number of lifelong or annual attacks (p > 0.3), comorbid diseases, or self-reported effect of triptans (p = 1) did not differ. HFEM patients purchased more triptans than CM patients (p = 0.01). CM patients received more early pension (p = 0.00135) but did not differ from HFEM patients with regard to sickness benefit (p = 0.207), cash assistance (p = 0.139), or rehabilitation benefit (p = 1). Discussion: Patients with HFEM are comparable to CM patients with regard to chronicity and disability. We therefore suggest classifying CM as ≥ 8 migraine days per month (proposed CM), disregarding the need for ≥ 15 headache days per month. The proposed diagnostic criteria for CM approximately doubled the number of patients with CM in both the Danish and the Russian materials. Extending the definition of CM to include patients with HFEM will ensure that patients with significant disease burden and unmet treatment needs are identified and provided appropriate access to the range of treatment options and resources available to those with CM. Conclusion: Patients with migraine on eight or more days but not 15 days with headache a month are as disabled as patients with ICHD-3 defined CM. They should be included in revised diagnostic criteria for chronic migraine.