Observational prospective pilot study to analyze the trajectory of neuroinflammatory protein expression in cerebrospinal fluid (CSF) in relation to systemic compartment in patients undergoing thoracic aortic surgery. The aim of this study is to identify and unravel the biochemical (neuroinflammatory) pathways involved in postoperative delirium. Patient undergoing thoracic aortic surgery will have an external lumbar drain (ELD) in situ on the day before surgery. This ELD remains in place during and three days after surgery to reduce the risk on periprocedural spinal cord ischemia. Paired measurements of CSF and blood will be analyzed.