Avijgan M, et al. - Researchers sought to ascertain the diagnostic criteria employed in randomized controlled trials to establish trial participants as having cervicogenic headache (CeH). Via performing a systematic review guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement, two independent reviewers identified most trials cited 1 (31/39; 79.5%) or more (3/39; 7.6%) references to describe the criteria used to recognize CeH in their study participants. Evidence gained here indicated the heterogeneity in the clinical characteristics used to diagnose CeH in participants recruited in randomized controlled trials. This questions the utility of the available randomized controlled trials to ascertain the clinical merits of the treatment and management of cases with CeHs. In this systematic review, it was noted that most randomized controlled trials printed to date have studied headaches with a clinical presentation involving the neck that may be better described as “possible,” “probable,” or “definitive” CeH depending on how well the diagnostic criteria used align with the most recent edition (3rd) of the International Classification of Headache Disorders.