MAPT and Alzheimer disease: Lower CSF β-amyloid protein/tau ratio has been associated with patients who develop perioperative neurocognitive disorder, suggesting a possible trajectory toward dementia after exposure to anesthesia and surgery.10–12 Changes in Alzheimer’s disease markers and astroglial cell integrity, as well as evidence for blood–brain barrier opening were also found in the CSF of patients after hip arthroplasty,13 confirming some of the earlier findings by Tang et al14 for idiopathic nasal CSF leak correction after surgery.