Nardone R et al. (2006) Trigemino-cervical reflex abnormalities in patients with migraine and cluster headache. Headache [doi: 10.1111/j.1526-4610.2006.00529.x]

Abnormalities in the trigemino-cervical reflex have been associated with headache. To assess the role of the trigeminal system in head pain, researchers in Italy studied the response in the sternocleidomastoid muscle to stimulation of the infraorbital nerve in 30 patients with migraine, 10 patients with cluster headache and 15 healthy controls.

Compared with controls, the trigemino-cervical response was abnormal during headache in 25 patients with migraine and 5 patients with cluster headache. In the inactive phase, an abnormal response was found in 20 patients with migraine and 1 patient with cluster headache. The observed abnormalities were unilateral in cluster headache and bilateral in migraine. Differences in responses were significant (P <0.001) between all patients with headache and controls during the headache phase. In the inactive phase, differences between migraine patients and controls were significant (P <0.001), but there was no significant difference between controls and patients with cluster headache.

The authors state that the bilateral nature of the abnormal response and the persistence of the abnormality in the inactive phase indicate a centrally located brainstem dysfunction in patients with migraine and suggest the involvement of central pain mechanisms in the disease. The results of the study offer support for the theory that abnormal brainstem modulation of nociceptive afferent neurons is involved in migraine pathogenesis. The authors say that different mechanisms are likely to be responsible for cluster headache, however.