['Tau is a protein localized primarily in neurons, especially in the axonal compartment. Cerebrospinal fluid tau levels are elevated in acute stroke and head traumas. The purpose of this study is to elucidate the alterations of cerebrospinal fluid tau levels in patients with or without neurologic complication after aortic surgery.', 'Twenty-eight patients undergoing descending thoracic (n = 8) or thoracoabdominal (n = 20) aortic surgery were enrolled. Cerebrospinal fluid tau levels were measured before operation and at seven time points up to the 72nd postoperative hour, and were compared with cerebrospinal fluid S100B levels.', 'Two patients developed brain infarction, including the one with paraplegia. In these patients, 20-fold to 100-fold tau elevation was observed, but S100B elevation was less evident in the patient without paraplegia. Three other patients developed spinal cord injury. Additional three patients suffered from temporary neurologic dysfunction of the brain. Tau levels in the latter three patients showed tenfold elevation and were higher than those in the three patients with spinal cord injury or those in the patients without neurologic complication up to 24 postoperative hours. The S100B levels were also higher in the three patients with temporary neurologic dysfunction of the brain than in the patients without neurologic complication at the conclusion of surgery. From 6 to 24 postoperative hours, they were higher in the three patients with spinal cord injury than in the patients without neurologic complication.'] Is tau protein in the cerebrospinal fluid a marker of brain injury after aortic surgery?