Photophobia and autonomic responses to facial pain in migraine.

Subjective and autonomic responses to visual stimulation and facial pain were investigated in 10 migraine sufferers and 21 'non-headache' control subjects. Ratings of glare- and light-induced pain were greater in migraine sufferers than control subjects. In migraine sufferers, glare ratings increased during painful mechanical stimulation of the nasal ala, the side of the nose and the back of the neck. Glare ratings decreased in both groups during painful stimulation of the chin. Light-induced pain increased during painful stimulation of all four sites in migraine sufferers, but not control subjects. Increases in forehead pulse amplitude during painful mechanical stimulation were greater bilaterally in migraine sufferers than in control subjects, consistent with loss of inhibitory influences on vascular reactions in the face. Visual stimulation facilitated lacrimation when the nasal ala was pinched, but visual stimulation coupled with pain elsewhere in the head and neck did not. The lacrimal response to combined nasal ala and visual stimulation was absent on the symptomatic side in patients with unilateral headache, indicating local parasympathetic deficit in migraine. These findings suggest that migraine is associated with loss of inhibitory subcortical processes which normally suppress sensations of glare and light-induced pain, and which may also suppress vasodilator responses to facial pain. Loss of inhibitory pain-control mechanisms could interact in a vicious circle with autonomic disturbances during migraine.