Migraine Outcome Should Not Be Used to Determine Diagnosis, Severity, and Therapy: Moving Towards a Multiparametric Definition of Chronicity

Chronic migraine (CM) diagnosis is nowadays based on the threshold of 15 headache days/month for three consecutive months, of which at least eight have migraine headache features. In recent years, proposals for reducing the threshold to 8 days/month have been proposed. The sole frequency parameter, however, is partial considering the variability in frequency, pain severity, associated symptoms, such as nausea, osmophobia, and photophobia, and presence of aura, but also the variable response to treatment and the association with several comorbidities. Therefore, in our opinion, a multiparameter perspective has to be taken into account that considers the underlying pathophysiology, in particular the presence of tension-type-like pain, cutaneous allodynia, and reduced pain threshold. A paradigm change in the definition of chronic migraine moves far beyond the mere 8 vs. 15 days/month, but has ethical and practical implications for treatment: should patients be treated with the most effective prophylactic drugs, i.e., monoclonal antibodies (MABs), if they enter into a new definition of CM? How should clinicians deal with treatment escalation towards MABs? What is the role of associated conditions, response to treatments, lifestyle issues, and psychological factors? And, finally, which endpoint should we use to define effectiveness? Is improvement in headache frequency enough, or should we move towards disability, quality of life, or workplace productivity?