Diagnostic integration of ICHD-3 and ICOP

Persistent headache and orofacial pain disorders often present overlapping clinical manifestations, sharedtrigeminal pathways, and common mechanisms of peripheral and central sensitization, making differentialdiagnosis challenging. Although the International Classification of Headache Disorders, 3rd edition (ICHD-3),and the International Classification of Orofacial Pain (ICOP) provide complementary diagnostic frameworks,their combined application in clinical practice remains underexplored. This narrative review critically examineshow the complementary use of the ICHD-3 and ICOP can contribute to the differential diagnosis of patientswith headache, facial pain, or intraoral pain. A literature search was conducted across PubMed/MEDLINE,Scopus, Embase, and Web of Science databases, prioritizing international classification documents, consensusstatements, clinical guidelines, systematic reviews, and high-quality narrative reviews. Available evidencedemonstrates substantial overlap between headache disorders and persistent orofacial pain, mediated byshared trigeminal mechanisms, neuroinflammation, and altered pain modulation. However, differences inpain distribution, temporal profile, somatosensory findings, autonomic manifestations, and the relationshipbetween symptom onset and trauma or dental procedures remain fundamental to differential diagnosis. Thecomplementary application of the ICHD-3 and ICOP offers a broader framework for assessing patients withoverlapping craniofacial pain presentations and may support more consistent diagnosis and multidisciplinarymanagement. Nevertheless, prospective studies are needed to determine whether this integrated diagnosticapproach improves diagnostic agreement, clinical decision-making, and patient outcomes.