Figure 2.

Schematic drawing illustrating the preclinical setting for cluster-like head pain.

Notes: The trigemino-autonomic reflex is suspected to contribute to cluster attack onset and autonomic symptoms (lacrimation flow, nasal congestion). Activation of the nucleus salivatorius superior induces the parasympathetic vasodilatation pathway involving the modulation of TCC neurons and related circuits and evokes autonomic features of cluster headache. From Akerman S, Goadsby PJ. Neuronal PAC1 receptors mediate delayed activation and sensitization of trigeminocervical neurons: Relevance to migraine. Sci Transl Med. 2015;7(308):308ra157. Reprinted with permission from AAAS.⁴⁶

Abbreviations: SuS, nucleus salivatorius superior; TG, trigeminal ganglion; TCC, trigeminocervical complex; SPG, ganglion sphenopalatinum.