Oxygen Inhibits Neuronal Activation in the Trigeminocervical Complex After Stimulation of Trigeminal Autonomic Reflex, But Not During Direct Dural Activation of Trigeminal Afferents

Trigeminal autonomic cephalalgias, including cluster headache, are characterized by unilateral head pain in association with ipsilateral cranial autonomic features. They are believed to involve activation of the trigeminovascular system and the parasympathetic outflow to the cranial vasculature from the superior salivatory nucleus (SuS) projections through the sphenopalatine ganglion, via the greater petrosal nerve of the VIIth (facial) cranial nerve. Cluster headache is remarkably responsive to treatment with oxygen, and yet our understanding of its mode of action is unknown.