1. From the Emergency Headache Center (A.D., U.F.), Head and Neck Clinic, Lariboisière Hospital, Paris, France; the Department of Neurology (A.D., U.F., C.S., M.-G.B.), Head and Neck Clinic, Lariboisière Hospital, Paris, France; the Department of Biostatistics (R.P.), Saint Louis Hospital; and the Department of Neuroradiology (M.B.), Head and Neck Clinic, Lariboisière Hospital, Paris, France; all from the APHP (Assistance Publique des Hôpitaux de Paris) and the Université Paris Diderot, Paris,...