Cognitive assessment will be conducted by trained research members who are blinded to the clinical diagnosis, treatment and MRI. The Mini-mental State Examination, Montreal cognitive assessment-basic, Mini-Mental State Examination telephone scales, Montreal Cognitive Assessment telephone scales, and Telephone Interview of Cognitive Status scale will be used to assess the cognitive function. Postoperative cognitive dysfunction is defined as at least 2 standard deviation reduction on the Mini-Mental State Examination telephone scales or Montreal Cognitive Assessment telephone scales or a Telephone Interview of Cognitive Status scale scores≤27.