Pupillary abnormalities due to sympathetic dysfunction in different forms of idiopathic headache

Idiopathic vascular-type headache is frequently associated with pupillary alteration, which is often presumed to be due to malfunction of the sympathetic nervous system. In this review the anatomical and neurotransmitter basis of oculosympathetic function is briefly discussed along with some of the common pharmacological and physiological pupillary tests used in its assessment. The clinical and subclinical features of the pupil abnormalities are analysed in idiopathic headache, which includes migraine, tension headache, cluster headache, and chronic paroxysmal hemicrania. Possible mechanisms underlying these alterations are suggested. Among secondary headaches, carotid dissection and aneurysm have to be excluded when unilateral headache is associated with a persistent ipsilateral oculosympathetic deficit. From the literature, specific responses to pupillary tests apparently are present in idiopathic headache. Pupillary tests may differentiate between the subtypes of idiopathic headache. The investigation of pupillary dysfunction may provide information on the physiopathological basis of headache.