Background.— Cluster headache is characterized by strictly unilateral head pain associated with symptoms of cranial autonomic features. Transcranial Doppler studies showed in most studies a bilateral decreased blood flow velocity in the middle cerebral artery.
Objective.— To investigate whether there is a bilateral or unilateral extracranial vasodilation during spontaneous cluster headache attacks.
Design and methods.— In 9 cluster headache patients, we investigated the luminal diameter of the superficial temporal artery with ultrasound on the headache and headache-free side during and outside cluster headache attacks.
Results.— During cluster headache attacks, the diameter of the superficial temporal artery on the painful side was greater, 1.48 mm, than the diameter on the nonheadache site, 1.14 mm (P < .01). Outside attacks, median diameters on the 2 sides were quite comparable, 1.34 vs 1.31 mm (P = .67).
Conclusions.— What was observed is most likely a general pain-induced arterial vasoconstriction (confer the decrease in diameter on the pain-free side) with an unchanged superficial temporal artery on the pain side because of some vasodilator influence.