No large prospective study has been able to definitively elucidate the mechanisms of perioperative stroke. Kam and Calcroft27 et al suggest that the most likely mechanisms include hypotension, cardiogenic thrombosis (especially atrial fibrillation or abnormal ventricular wall motion), atheromatous plaque leading to thrombosis or embolism (or hemodynamic stroke associated with destruction of cerebrovascular reserve), and perioperative hypercoagulable state. Perioperative strokes tend to occur in the first postoperative week.23,27 Therefore, it is hypothesized that surgical strikes have an important place in the genesis of stroke. Most strokes arise from thrombosis or embolism, but some arise from defects in cerebrovascular reserve capacity in the context of the altered perioperative physiological environment. Hypercoagulable states are the result of perioperative stress.28 The combination of patient and surgical factors increases the likelihood of thrombosis or embolism, leading to an ischemic stroke. Abnormal anatomic access between the patient’s veins and large arteries may also be a particular risk factor. A number of conditions may lead to decreased local blood flow, including surgical manipulation, cerebral or carotid artery stenosis, head position, or low cardiac displacement due to low (or no) power in the ventricular wall. Head position, in particular, increases the risk of vertebrobasilar system, as previously described. Arrhythmias, especially atrial fibrillation, are also very important factors. Atrial fibrillation is relatively common in the postoperative period and may be another cause of stroke in the postoperative period. Perioperative erythrocytosis, although uncommon, may also cause thrombosis. Operating on or near the carotid artery is particularly dangerous for embolic phenomena.