Baseline tear fluid CGRP is elevated in active cluster headache patients as long as they have not taken attack abortive medication.

This study shows that active cluster headache patients have increased calcitonin gene-related peptide levels in tear fluid compared to healthy subjects, which are reduced to control levels after intake of attack abortive medication. Calcitonin gene-related peptide measurement in tear fluid is non-invasive, and has the advantage of allowing direct access to calcitonin gene-related peptide released from the trigeminal nerve.