The heterogeneity of migraine and other headache disorders, including their variable clinical presentations, may present diagnostic challenges. The Headache Classification Committee of the International Headache Society has recently published the 3rd edition of The International Classification of Headache Disorders (ICHD-3) with detailed diagnostic criteria for a hierarchical classification of headaches and migraines.1
As a part of the Comprehensive Migraine Update I course during the AAN 2019 Annual Meeting, Prof. Morris Levin (UCSF Medical Center) spoke about the Diagnosis of Chronic Migraine. Prof. Levin explained that one of the challenges of migraine diagnosis is the fact that the same patient may suffer from different types of headaches at different times. The recommendation in ICHD-3 is that each distinct type, subtype, or subform of headache should be separately diagnosed and coded.
Quoting the ICHD-3 classification, Prof. Levin defined chronic migraine as headaches occurring on 15 or more days per month—at least 8 of which have the features of migraine headaches—for more than three months.1 However, Prof. Levin noted that medication overuse may also lead to frequent migraine attacks. In this context, he posited that chronic migraine associated with medication overuse should be diagnosed both as chronic migraine and medication-overuse headache (MOH).1 Prof. Levin argued that differentiating chronic migraine from MOH requires an assumption of causality. For example, a significant improvement in headaches upon discontinuation or reduction of acute medications is typically indicative of MOH.
When diagnosing chronic migraine, Prof. Levin emphasized the importance of assessing how the headaches originally developed, and recognizing typical patterns of the various types of primary and secondary headaches—e.g. tension type headaches, trigeminal autonomic cephalalgias (TAC), exertional headaches, vascular diseases, and post-traumatic headaches.2 Prof. Levin reviewed further useful key diagnostic criteria, including the nature of the pain, associated symptoms, medical history, and response to attempted treatments. He concluded that a comprehensive and systematic diagnosis of chronic migraine is the key to determining the appropriate treatment approach for each patient.2