Red and orange flags for secondary headaches in clinical practice

From the Headache Diagnostic Laboratory (T.P.D., H.W.S.), Danish Headache Center and Department of Neurology (J.M.H.), Rigshospitalet-Glostrup, Faculty of Health Sciences, University of Copenhagen, Glostrup, Denmark; Department of Neurology (A.R., G.G.S.), Elisabeth-TweeSteden Hospital, Tilburg, the Netherlands; Department of Neurology (C.S.), Inselspital, Bern University Hospital, University of Bern, Switzerland; Department of Neurology and Anesthesiology/Critical Care Medicine (S.E.N.), Johns Hopkins University, Baltimore, MD; Center for Neurology (M.O.), Asklepios Hospitals Schildautal, Seesen; Department of Neurology (M.O.), University Hospital Essen, University of Duisburg-Essen, Germany; Neurometabolism (A.J.S.), Institute of Metabolism and Systems Research, College of Medical and Dental Sciences, University of Birmingham, UK; and Neurorehabilitation (A.R.G.), RehaClinic Bad Zurzach and University of Zürich, Switzerland.

From the Headache Diagnostic Laboratory (T.P.D., H.W.S.), Danish Headache Center and Department of Neurology (J.M.H.), Rigshospitalet-Glostrup, Faculty of Health Sciences, University of Copenhagen, Glostrup, Denmark; Department of Neurology (A.R., G.G.S.), Elisabeth-TweeSteden Hospital, Tilburg, the Netherlands; Department of Neurology (C.S.), Inselspital, Bern University Hospital, University of Bern, Switzerland; Department of Neurology and Anesthesiology/Critical Care Medicine (S.E.N.), Johns Hopkins University, Baltimore, MD; Center for Neurology (M.O.), Asklepios Hospitals Schildautal, Seesen; Department of Neurology (M.O.), University Hospital Essen, University of Duisburg-Essen, Germany; Neurometabolism (A.J.S.), Institute of Metabolism and Systems Research, College of Medical and Dental Sciences, University of Birmingham, UK; and Neurorehabilitation (A.R.G.), RehaClinic Bad Zurzach and University of Zürich, Switzerland.

From the Headache Diagnostic Laboratory (T.P.D., H.W.S.), Danish Headache Center and Department of Neurology (J.M.H.), Rigshospitalet-Glostrup, Faculty of Health Sciences, University of Copenhagen, Glostrup, Denmark; Department of Neurology (A.R., G.G.S.), Elisabeth-TweeSteden Hospital, Tilburg, the Netherlands; Department of Neurology (C.S.), Inselspital, Bern University Hospital, University of Bern, Switzerland; Department of Neurology and Anesthesiology/Critical Care Medicine (S.E.N.), Johns Hopkins University, Baltimore, MD; Center for Neurology (M.O.), Asklepios Hospitals Schildautal, Seesen; Department of Neurology (M.O.), University Hospital Essen, University of Duisburg-Essen, Germany; Neurometabolism (A.J.S.), Institute of Metabolism and Systems Research, College of Medical and Dental Sciences, University of Birmingham, UK; and Neurorehabilitation (A.R.G.), RehaClinic Bad Zurzach and University of Zürich, Switzerland.

From the Headache Diagnostic Laboratory (T.P.D., H.W.S.), Danish Headache Center and Department of Neurology (J.M.H.), Rigshospitalet-Glostrup, Faculty of Health Sciences, University of Copenhagen, Glostrup, Denmark; Department of Neurology (A.R., G.G.S.), Elisabeth-TweeSteden Hospital, Tilburg, the Netherlands; Department of Neurology (C.S.), Inselspital, Bern University Hospital, University of Bern, Switzerland; Department of Neurology and Anesthesiology/Critical Care Medicine (S.E.N.), Johns Hopkins University, Baltimore, MD; Center for Neurology (M.O.), Asklepios Hospitals Schildautal, Seesen; Department of Neurology (M.O.), University Hospital Essen, University of Duisburg-Essen, Germany; Neurometabolism (A.J.S.), Institute of Metabolism and Systems Research, College of Medical and Dental Sciences, University of Birmingham, UK; and Neurorehabilitation (A.R.G.), RehaClinic Bad Zurzach and University of Zürich, Switzerland.

From the Headache Diagnostic Laboratory (T.P.D., H.W.S.), Danish Headache Center and Department of Neurology (J.M.H.), Rigshospitalet-Glostrup, Faculty of Health Sciences, University of Copenhagen, Glostrup, Denmark; Department of Neurology (A.R., G.G.S.), Elisabeth-TweeSteden Hospital, Tilburg, the Netherlands; Department of Neurology (C.S.), Inselspital, Bern University Hospital, University of Bern, Switzerland; Department of Neurology and Anesthesiology/Critical Care Medicine (S.E.N.), Johns Hopkins University, Baltimore, MD; Center for Neurology (M.O.), Asklepios Hospitals Schildautal, Seesen; Department of Neurology (M.O.), University Hospital Essen, University of Duisburg-Essen, Germany; Neurometabolism (A.J.S.), Institute of Metabolism and Systems Research, College of Medical and Dental Sciences, University of Birmingham, UK; and Neurorehabilitation (A.R.G.), RehaClinic Bad Zurzach and University of Zürich, Switzerland.

From the Headache Diagnostic Laboratory (T.P.D., H.W.S.), Danish Headache Center and Department of Neurology (J.M.H.), Rigshospitalet-Glostrup, Faculty of Health Sciences, University of Copenhagen, Glostrup, Denmark; Department of Neurology (A.R., G.G.S.), Elisabeth-TweeSteden Hospital, Tilburg, the Netherlands; Department of Neurology (C.S.), Inselspital, Bern University Hospital, University of Bern, Switzerland; Department of Neurology and Anesthesiology/Critical Care Medicine (S.E.N.), Johns Hopkins University, Baltimore, MD; Center for Neurology (M.O.), Asklepios Hospitals Schildautal, Seesen; Department of Neurology (M.O.), University Hospital Essen, University of Duisburg-Essen, Germany; Neurometabolism (A.J.S.), Institute of Metabolism and Systems Research, College of Medical and Dental Sciences, University of Birmingham, UK; and Neurorehabilitation (A.R.G.), RehaClinic Bad Zurzach and University of Zürich, Switzerland.

From the Headache Diagnostic Laboratory (T.P.D., H.W.S.), Danish Headache Center and Department of Neurology (J.M.H.), Rigshospitalet-Glostrup, Faculty of Health Sciences, University of Copenhagen, Glostrup, Denmark; Department of Neurology (A.R., G.G.S.), Elisabeth-TweeSteden Hospital, Tilburg, the Netherlands; Department of Neurology (C.S.), Inselspital, Bern University Hospital, University of Bern, Switzerland; Department of Neurology and Anesthesiology/Critical Care Medicine (S.E.N.), Johns Hopkins University, Baltimore, MD; Center for Neurology (M.O.), Asklepios Hospitals Schildautal, Seesen; Department of Neurology (M.O.), University Hospital Essen, University of Duisburg-Essen, Germany; Neurometabolism (A.J.S.), Institute of Metabolism and Systems Research, College of Medical and Dental Sciences, University of Birmingham, UK; and Neurorehabilitation (A.R.G.), RehaClinic Bad Zurzach and University of Zürich, Switzerland.

From the Headache Diagnostic Laboratory (T.P.D., H.W.S.), Danish Headache Center and Department of Neurology (J.M.H.), Rigshospitalet-Glostrup, Faculty of Health Sciences, University of Copenhagen, Glostrup, Denmark; Department of Neurology (A.R., G.G.S.), Elisabeth-TweeSteden Hospital, Tilburg, the Netherlands; Department of Neurology (C.S.), Inselspital, Bern University Hospital, University of Bern, Switzerland; Department of Neurology and Anesthesiology/Critical Care Medicine (S.E.N.), Johns Hopkins University, Baltimore, MD; Center for Neurology (M.O.), Asklepios Hospitals Schildautal, Seesen; Department of Neurology (M.O.), University Hospital Essen, University of Duisburg-Essen, Germany; Neurometabolism (A.J.S.), Institute of Metabolism and Systems Research, College of Medical and Dental Sciences, University of Birmingham, UK; and Neurorehabilitation (A.R.G.), RehaClinic Bad Zurzach and University of Zürich, Switzerland.

From the Headache Diagnostic Laboratory (T.P.D., H.W.S.), Danish Headache Center and Department of Neurology (J.M.H.), Rigshospitalet-Glostrup, Faculty of Health Sciences, University of Copenhagen, Glostrup, Denmark; Department of Neurology (A.R., G.G.S.), Elisabeth-TweeSteden Hospital, Tilburg, the Netherlands; Department of Neurology (C.S.), Inselspital, Bern University Hospital, University of Bern, Switzerland; Department of Neurology and Anesthesiology/Critical Care Medicine (S.E.N.), Johns Hopkins University, Baltimore, MD; Center for Neurology (M.O.), Asklepios Hospitals Schildautal, Seesen; Department of Neurology (M.O.), University Hospital Essen, University of Duisburg-Essen, Germany; Neurometabolism (A.J.S.), Institute of Metabolism and Systems Research, College of Medical and Dental Sciences, University of Birmingham, UK; and Neurorehabilitation (A.R.G.), RehaClinic Bad Zurzach and University of Zürich, Switzerland.

From the Headache Diagnostic Laboratory (T.P.D., H.W.S.), Danish Headache Center and Department of Neurology (J.M.H.), Rigshospitalet-Glostrup, Faculty of Health Sciences, University of Copenhagen, Glostrup, Denmark; Department of Neurology (A.R., G.G.S.), Elisabeth-TweeSteden Hospital, Tilburg, the Netherlands; Department of Neurology (C.S.), Inselspital, Bern University Hospital, University of Bern, Switzerland; Department of Neurology and Anesthesiology/Critical Care Medicine (S.E.N.), Johns Hopkins University, Baltimore, MD; Center for Neurology (M.O.), Asklepios Hospitals Schildautal, Seesen; Department of Neurology (M.O.), University Hospital Essen, University of Duisburg-Essen, Germany; Neurometabolism (A.J.S.), Institute of Metabolism and Systems Research, College of Medical and Dental Sciences, University of Birmingham, UK; and Neurorehabilitation (A.R.G.), RehaClinic Bad Zurzach and University of Zürich, Switzerland.