CUTANEOUS SENSORY STIMULATION LEADING TO FACIAL FLUSHING AND RELEASE OF CALCITONIN GENE-RELATED PEPTIDE

A patient is described with a 17-year history of intractable left-sided facial pain. The pain occurred daily in 5 sec spasms to a maximum of one every 2-3 min and was restricted to the left upper face. It was associated with rhinorrhoea on the left and often with ipsilateral facial flushing. Conventional therapy, including carbamazepine, baclofen and three posterior fossa explorations, had not provided lasting relief. Local facial stimulation by tapping a painful trigger point led to both pain and flushing of the face ipsilaterally. During this flushing, blood was collected and assayed using sensitive radioimmunoassays for several neuropeptides (neuropeptide Y, substance P, vasoactive intestinal polypeptide and calcitonin gene-related peptide). A marked (119%) increase in calcitonin gene-related peptide was noted in the external jugular vein blood ipsilaterally during the flushing with no change in the other peptides measured. To quantitate the effect of calcitonin gene-related peptide on human extracranial vessels, standard pharmacological procedures were used to examine the potency of the peptide as a vasodilator of human facial artery. The IC50 of calcitonin gene-related peptide for the prostaglandin F(2-alpha)-precontracted human facial artery was 10(-9) mol/l. The relevance of these observations to the clinical problem of migraine is considered.