VIP and Headache: A better response has been seen in: CM patients with unilateral headache, pericranial allodynia and pericranial muscle tenderness [34, 35]; those with imploding headache and ocular headache [36]; those with a shorter disease duration (<30 years) [37]; and those with elevated interictal plasma levels of CGRP and vasoactive intestinal peptide (VIP) [38].