Cluster-migraine: does it exist?

The nosological boundaries between cluster headache and migraine are sometimes ill-defined. Although the two disorders are distinct clinical entities, patients sometimes present with clinical scenarios having characteristics of both headache types, but either do not fully meet International Classification of Headache Disorders, Second Edition diagnostic criteria for either disorder or have sufficient symptoms and signs to allow both diagnoses to be present. These occasions provide diagnostic challenges and include what is variously described as migraine-cluster, cyclical migraine, clustering episodes of migraine, cluster with aura, or atypical cluster without autonomic symptoms or severe pain. Patients with symptoms overlapping cluster headache and migraine likely reflect the inherent clinical variability in each of these two disorders, rather than distinct diagnostic entities in their own right.