Characterization of trigeminal C‐fiber reactivity through capsaicin‐induced release of calcitonin gene‐related peptide.

Objective: We hypothesized that the response of trigeminal dermal blood flow (DBF) in the trigeminal system and consecutive expansion of flare response to capsaicin would differ from the somatosensory system (arm). We also investigated whether there are differences between patients with migraine and healthy controls (HC). Background: Functional differences between the trigeminal and extracephalic somatosensory systems may partly explain the susceptibility for headaches in patients with migraine. Capsaicin‐induced activation of nociceptive C‐fibers in the skin is mainly mediated by calcitonin gene‐related peptide (CGRP) and induces cutaneous vessel dilatation and flare response. Methods: Female patients with migraine (n = 38) and age‐matched HC (n = 35) underwent DBF measurement at baseline and after topical capsaicin administration using laser speckle imaging. DBF before and after capsaicin stimulation was analyzed over ophthalmic nerve/maxillary nerve/mandibular nerve (V1/V2/V3) dermatomes and the forearm as an extracephalic control. Results: Capsaicin‐induced DBF increased more in the trigeminal dermatomes than on the forearm. The V1 dermatome showed a smaller increase of DBF in patients with migraine compared to HC. Conclusion: Our results suggest that the trigeminovascular system reacts differently from extracephalic areas, which may explain the trigeminal susceptibility to CGRP‐mediated pain attacks. By demonstrating a different reactivity of the V1 dermatome in patients with migraine, our finding suggests that the first trigeminal branch is functionally different from the second and third branches; however, only in patients with migraine. [ABSTRACT FROM AUTHOR]