HEADACHE CURRENTS – CLINICAL REVIEW Operational Diagnostic Criteria for Chronic Migraine: Expert Opinion Stephen D. Silberstein, MD; Richard B. Lipton, MD; David W. Dodick, MD Objective.—The prevalence, disability, progression, and treatment needs associated with chronic migraine (CM) mandate epidemiological, clinical, and basic research to better understand the clinical course of this disorder and to facilitate development of more effective therapies. Such efforts have been significantly impeded by lack of agreement within the headache specialist community of the most appropriate diagnostic criteria for CM. Methods.—This paper reviews the pertinent nosological literature and extensive field testing already performed. Results.—We recommend that the International Classification of Headache Disorders-3β criteria for CM be modified. We would remove the need for 5 prior migraine attacks and would replace “Headache considered by patient to be onset migraine and relieved by a triptan or an ergotamine derivative” with “criteria A and B for 1.5 probable migraine.” Conclusions.—The proposed criteria are guided by the aims of accurately characterizing patients with migraine who develop primary chronic daily headache, reflecting the large numbers of patients with CM in clinical practice, and facilitating research into a disorder that is an academic and clinical priority. Key words: medication overuse headache, chronic migraine, diagnostic cri- teria, International Classification of Headache Disorders-3 The term chronic daily headache (CDH) refers to a group of disorders characterized by very frequent headaches (15 or more days a month) for at least 3 months. 1,2 CDH is a significant public health concern. Approximately 3-5% of the population worldwide experiences daily or near-daily headaches. 3-7 Patients with CDH experience diminished quality of life and mental health as well as impaired physical, social, and occupational functioning. 8-12 In addition, they account for substantial direct medical costs and are the major reason for headache subspecialty practice consultations in the United States. 13,14 Table 1 outlines the most common primary headache disor- ders organized by frequency (chronic vs episodic) and duration (long attacks vs short attacks). 15 In subspecialty practice, the most common form of CDH is a form of very frequent migraine that was previously termed transformed migraine (TM) and is now called chronic migraine (CM). The estimated prevalence of CM/TM worldwide is 1-3%; prevalence varies by case definition, case ascertainment, population, ethnicity, and other variables. 15-20 Patients with CM experience pain and other symptoms, includ- ing nausea, vomiting, photophobia, and phonophobia, at least half of their days and are disabled by the disorder. 14,21 CM is more debilitating than episodic migraine. 15 In 1 study, 12,22 the number of lost days per 3 months was higher in CM than in episodic migraine for every category of self-reported function examined, including missed work or school (2.4 vs 0.5); ≥50% reduced productivity at work or school (10.4 vs 1.7); missed household work or chores (21.4 vs 3.5); ≥50% reduced productivity in household work or chores (18.7 vs 2.6); and missed days of family, social, or leisure activity (10.5 vs 1.7). CM often evolves from episodic migraine over months to years. Recent research suggests that CM is associated with brain abnor- malities that are progressive and could be persistent or perma- nent. 23,24 CM has been characterized as the most important challenge today for tertiary headache centers, where more than 50% of patients are referred. 25 Progress in research and the development of new treatments for CM has been hampered by lack of agreement on the diag- nostic criteria. 18,26 CM definitions have in common the require- ment of very frequent headaches and a link to migraine. The debate has centered on 2 major issues. First, what are the optimal rules for establishing a link to migraine? The major alternative approaches are summarized in Table 1. Second, how do we evalu- ate CM in the setting of medication overuse? This paper reviews the pertinent nosological literature including the recently From the Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA, USA (S.D. Silberstein); Albert Einstein College of Medicine, Bronx, NY, USA (R.B. Lipton); Mayo Clinic, Scottsdale, AZ, USA (D.W. Dodick). Address all correspondence to S.D. Silberstein, Neurology,Thomas Jefferson University, Suite 8130, 111 South 11th Street, Gibbon Building, Philadelphia, PA 19107, USA. Accepted for publication: May 14, 2014. ............. Headache © 2014 American Headache Society ............. Conflict of Interest: Dr. Dodick has served on advisory boards and has consulted for Allergan, Amgen, Alder, Arteaus, Pfizer, Merck, ENeura, NuPathe, Eli Lilly & Company, Autonomic Technologies, WL Gore, Ethicon J&J, Zogenix, Supernus, Labrys, and Bristol Myers Squibb. Dr. Dodick has received funding for travel, speaking, or editorial activities from the following: CogniMed, Scientiae, IntraMed, SAGE Publishing, Sun Pharma, Allergan, Lippincott Williams & Wilkins, Oxford University Press, Cambridge University Press, Miller Medical, SAGE, and Annenberg Center for Health Sciences; he serves as Editor-in-Chief and on the editorial boards of The Neurologist, Lancet Neurology, and Postgraduate Medicine, and has served as Editor-in- Chief of Cephalalgia. He receives publishing royalties for Wolff’s Headache, 8th edition (Oxford University Press, 2009) and Handbook of Headache (Cambridge University Press, 2010). Dr. Silberstein is on the advisory panel of and receives honoraria from Allergan, Artaeus, Electrocore, and Neuralieve. He serves as a consultant for and receives honoraria from Amgen, Labrys Biologics, MAP, and Zogenix. His employer receives research support from AGA, Allergan, Amgen, Cumberland, ElectroCore, Labrys, Merz, OptiNose, and Troy Healthcare. Dr. Lipton receives research support from the NIH – PO1 AG03949 (Program Director), PO1AG027734 (Project Leader), RO1AG025119 (Investigator), K23AGO30857 (Mentor), K23NS05140901A1 (Mentor), and K23NS47256 (Mentor), the National Headache Founda- tion and the Migraine Research Fund; serves on the editorial boards of Neurology and Cephal- algia and as senior advisor to Headache, has reviewed for the NIA and NINDS, holds stock options in Neuralieve, Inc., and Minster, Inc.; and serves as a consultant or has received honoraria from: Allergan, Autonomic Technologies, Boston Scientific, Bristol Myers Squibb, Eli Lilly, Endo, GlaxoSmithKline, Minster, Merck, Nautilus Neuroscience, Neuralieve, Novartis, and Pfizer. Headache Currents 1