Cerebral hyperperfusion syndrome (CHS) was initially described as a clinical syndrome following carotid endarterectomy (CEA), but it may present in both CEA and carotid artery stenting, and is characterised by throbbing ipsilateral frontotemporal or periorbital headache, and sometimes diffuse headache, eye and face pain, vomiting, confusion, macular oedema, and visual disturbances, focal motor seizures with frequent secondary generalisation, focal neurological deficits, and intracerebral or subarachnoid haemorrhage. Knowledge of CHS among physicians is limited. Most studies report incidences of CHS of 1-3% after carotid endarterectomy. CHS is most common in patients with increases of more than 100% in perfusion compared with baseline after carotid revascularization procedures and is rare in patients with increases in perfusion less than 100% compared with baseline. The pathophysiological mechanism of CHS remains only partially understood. The chronic lowflow state induced by severe carotid disease results in a compensatory dilation of cerebral vessels distal to the stenosis, as part of the normal autoregulatory response, to maintain adequate cerebral blood flow (CBF). In this chronically dilated state, the vessels lose their ability to autoregulate vascular resistance in response to changes in blood pressure. In fact, it has been shown that this dysautoregulation is proportional to the duration and severity of chronic hypoperfusion. After revascularization and reperfusion, the impaired cerebral autoregulation could then contribute to a cascade of intracranial microcirculatory changes, as explained above, with an inability of reaction toward the augmentation of the CBF after the carotid recanalization. Although most patients have mild symptoms and signs, progression to severe and life-threatening symptoms can occur if CHS is not recognised and treated adequately. Because CHS is a diagnosis based on several non-specific signs and symptoms, patients may be misdiagnosed as having one of the better-known causes of perioperative complications like thromboembolism.