Thermographic changes in cluster headache.

Eleven patients were examined thermographically during spontaneous cluster headaches and 22 during attacks induced by nitroglycerin or alcohol. In cluster headache, heat loss increased from the affected orbital region, and in some patients, this spread above and below the eye, down the nose, and to the affected temple. Inhalation of 100% oxygen reduced or abolished cluster pain in 22 of 25 instances, and asymmetry of heat loss then disappeared. Since the unilateral increase in blood flow usually followed the onset of pain in affected areas, the vascular changes of cluster headache are probably secondary phenomena, initiated by a vasodilator pathway, with the trigeminal nerve as the afferent and the greater superficial petrosal nerve as the efferent limb.