Cluster headache and head trauma: is there an association?

This article discusses what is known of and written regarding the possible association of cluster headache and head trauma. There is additional discussion of conditions other than direct head trauma that are also seen in association with cluster headache. These conditions bring into question the concept of primary versus secondary cluster headache and raise the possible need to expand the category of secondary cluster headache. With increasing knowledge of the pathophysiology of cluster headache, the potentially causative role of head trauma in the development of cluster headache may become better defined.