Migraine with aura (MA) is an independent risk factor for stroke and is associated with silent brain infracts and T2 white matter hyperintensities on MRI. Previous studies using Transcranial Doppler (TCD) have shown an impairment of cerebral autoregulation in MA patients. Studies with positron emission tomography have demonstrated an activation of brain stem areas during migraine attack. An increased density of brain stem grey matter as measured on MRI with voxel based morphometry (VBM) has been found in MA patients. As brain arteries and arterioles are innervated by ascending tracts from aminergic brainstem nuclei, th study hypothesize a negative correlation between the density of brainstem nuclei and the efficiency of cerebral autoregulation in MA patients compared with controls.