Atypical presentations of cluster headache.

Recently, cluster headache has been shown to occur with aura, suggesting that as more cluster patients are seen by headache specialists new forms of this well-defined primary headache syndrome will be identified. This study presents three atypical presentations of cluster headache: persistent or unremitting cluster, periodic cluster, and reflex or event-related cluster. Case reports are presented with an explanation as to why these headaches should be considered cluster headache.