What causes cluster headaches?

Very little is known about the source of cluster headaches. The best data available suggests that cluster headaches are somehow regulated by the posterior hypothalamic gray matter. This region of the brain is responsible for our circadian rhythms and our biologic functions such as appetite and temperature regulation. It is felt that a defect in this region occurs in patients who get cluster headaches and this is why they occur principally at night. The mechanism that triggers a series of cluster headaches and then eventually stops a series of cluster headaches is unknown.