title: A clinical approach: 3. Chronic head and facial pain [ii].
mesh_terms: D003027:Cluster Headache / Q000209:etiology; D005157:Facial Pain / Q000209:etiology; D006261:Headache / Q000145:classification / Q000209:etiology*; D006801:Humans; D008881:Migraine Disorders / Q000209:etiology