Reversible cerebral vasoconstriction syndrome (RCVS) is a clinico radiological entity characterized by severe headaches (associated or not with neurological complications) during one to 3 weeks, associated with a characteristic 'string and beads' appearance on cerebral arteries, which resolves spontaneously in 3 months. The pathway is unknown. At early stage of the disease (at the first medical consultation) cerebral arterial abnormalities which are necessary for diagnosis are identified in only 20% of patients (brain magnetic resonance imagery (MRI) ,CT scan angiography), appearing with a delay on 2th or 3rd week after the first severe headache..