Traumatic head injury in cluster headache: cause or effect?

Post-traumatic headache (PTH) is a common and well-recognized entity. Tension-type headache and migraine are the commonest phenotypes that can result from head trauma, while the onset of cluster headache (CH) in close temporal relation to a head trauma has only been described in rare cases. Nevertheless, CH patients seem to incur more frequent traumatic head injuries during their lifetimes when compared to migraine controls and the general population. The basis of this association remains unclear, since only a limited number of methodologically robust studies have examined it. However, three main hypotheses can be proposed to explain this association: head trauma is the direct cause of CH; head trauma is a risk factor for the future development of CH; and head trauma is a consequence of a CH trait. A better understanding of the association between head trauma and CH may provide important insights into both the pathophysiology of CH and the mechanisms by which traumatic head injury predisposes patients to developing headaches.