A major concern with cardiac surgery is neurological damage. Stroke occurs in 2–3% of all people undergoing cardiac surgery, and the rate is higher in patients with other risk factors for stroke.[24] A more subtle complication attributed to cardiopulmonary bypass is postperfusion syndrome, sometimes called "pumphead". The neurocognitive symptoms of postperfusion syndrome were initially thought to be permanent,[25] but turned out to be transient, with no permanent neurological impairment.[26]