Peripherally, PACAP is expressed in several cranial ganglia relevant to migraine and cluster headache biology, including the sphenopalatine ganglion (SPG)79, 80, 81, 82 and trigeminal ganglion,83, 84 which have been examined the most closely with regards to co‐expression of CGRP and PACAP.85, 86. Here, ADCYAP1 is linked to Cluster headache.