Dissociation between pain and autonomic disturbances in cluster headache. The relationship between pain and autonomic disturbances in cluster headache was studied in 54 patients whose attack always recurred on the same side, and in 7 others whose attack had affected either side on different occasions. In one of these seven patients, facial flushing and ocular sympathetic deficit was observed on the original side of headaches. In most patients, the orbital region was warmer on the painful side but in three cases this region was cooler during and between attacks. Lacrimation and rhinorrhoea were more common in severe attacks, and the temperature difference between the orbits increased with increasing severity of pain. These findings support the view that certain autonomic disturbances in cluster headache are provoked by pain. Residual autonomic dysfunction could influence autonomic activity during cluster headache. If so, residual dysfunction on the pain-free side could explain the dissociation between autonomic disturbances and pain observed in a few cases. 