Numerous patients are addressed to the Emergency Department for unspecific symptoms which can evoke a stroke, such as vertigo, isolated motor deficit, behavior disorder. For these patients, when they arrive out of time for specific treatments such as thrombolysis and thrombectomy, the cerebral imagery is not an emergency, but necessary to confirm or invalidate the diagnostic of stroke. If a biomarker could exclude the diagnostic of stroke, we could avoid an imagery for these patients. PS100B is a biomarker whose blood level increases in case of stroke. It has already proven a prognostic value. Until now, it hasn't proven a diagnostic value because it take a few hours to increase in the blood. It could have in prognostic value for patients who have the symptoms for more than 24 hours. STROkE is a diagnostic, prospective, monocentric study, conducted at University Hospital Center of Poitiers (France). The aim is to determine the value of PS100B to exclude the diagnostic of a stroke in case of evocative symptoms, for patients who are out of delay for a thrombolysis or a thrombectomy. Patients eligible are the ones who present to the emergency department with symptoms evocative of stroke for more than 24 hours and less than 4 days. Patients included have a sample of blood withdrawn, in order to measure PS100B blood level. The diagnostic of stroke is than confirmed or excluded by an adjudication comity, who are unaware of the result of PS100B blood level. The diagnostic value of PS100B is determined with the help of a ROC curve.