Biological markers of cervicogenic headache.

Upper cervical pain is frequent in different primary headaches and not sufficient evidence for cervicogenic headache (CH). Biological markers should help to differentiate CH from other headache disorders. In most cases, imaging techniques of the cervical spine are not helpful for the diagnosis of CH. Symptoms and signs of neck involvement, such as a mechanical precipitation of attacks, a restriction in range of motion of the cervical spine, and the existence of ipsilateral neck, shoulder, or arm pain, seem to be reasonably valid for the diagnosis of CH, but its reliability and validity should be confirmed in larger studies. Positive diagnostic blockades of cervical structures or its nerve supply are not specific for CH. Neurophysiological investigations give some insight into the pathophysiological mechanisms of CH but are not diagnostic. In CH, calcitonin gene-related peptide levels do not differ between the symptomatic and the asymptomatic side, between the jugular and the cubital blood, and between days with and without headache. There is no evidence for an activation of the trigeminovascular system in CH. It can be concluded that CH is not just a migraine variant triggered by neck dysfunction but a functional entity.