CALCA and Cluster headache: These keywords were mainly divided into 10 clusters: Cluster #0 ‘topiramate’, Cluster #1 ‘efficacy’, Cluster #2 ‘CGRP’, Cluster #3 ‘etiology’, Cluster #4 ‘central nervous system’, Cluster #5 ‘valproic acid’, Cluster #6 ‘dichotomous outcome measures’, Cluster #7 ‘cluster headache’, Cluster #8 ‘acute treatment’, and Cluster #9 ‘menstrually related migraine’.