title: Expert commentary -- unusual headache syndromes.
authors.affiliation: Head of the Merck Investigator Study Program, Scientific Engagement and Education, Office of the Chief Medical Officer-Merck, North Wales, PA, USA. marcelo_bigal@merck.com
authors.forename: Marcelo E
authors.initials: ME
authors.lastname: Bigal
mesh_terms: D003937:Diagnosis, Differential; D042241:Early Diagnosis; D005260:Female; D020773:Headache Disorders / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008881:Migraine Disorders / Q000175:diagnosis / Q000503:physiopathology