Migrainous features in cluster headache.

Migraine and cluster headache have been considered entirely separate clinical syndromes, both in routine clinical practice and in the 1988 International Headache Society classification. Neurologists seeing large numbers of patients soon realize, however, that there is a considerable overlap between the two conditions. Some patients have attacks with the cardinal features of cluster headache, but also have a few symptoms (especially a visual aura) usually attributed to migraine. In addition, it is not uncommon for a patient with a lifetime's history of migraine to experience a typical bout of cluster headache, although the reverse is less common. This article reviews the published series of such patients.