Although the study is observational any frontal severe EEG asymmetry together with the appearance of burst suppression will be carefully evaluated by an experienced anesthesiologist in reading and interpreting processed EEG monitor. The case will be discussed on an multidisciplinary basis and an eventual CT scan will be performed.In the absence of hemorrhage and if large cerebral vessel occlusion is identified, a catheter angiography with an eventual thrombectomy will be realized with the aim to extract the clot.