Postoperative cognitive dysfunction (POCD) is increasingly recognized as a important complication of surgery . POCD not only affect the quality of life, but also adds cost to hospitalization and out-of-hospital care. So the relationship between POCD and anesthesia and surgery merits more study. In the present study, we explore the abnormities of white mater (WM) in elderly patients with post-operative cognition disorders (POCD) using diffusion kurtosis magnetic resonance imaging (DKI).Participated in this 91 patients aged 70 to 93 years, scheduled for elective orthopedic, urologic, general or vascular surgeriesunder general or regional anesthesia. All the patients were evaluated with the Mini-Mental State Examination (MMSE) for cognitive function in the day before surgery (Day 0). MMSE was applied again 3 days after surgery (Day 3). POCD was defined as MMSE score below 20/30 or as a difference equal to or above 4 as compared to Day 0. The DKI data of all the participantts were obtained in Day 3 using a 3T MR scanner and postprocessed using DKE software package, Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD), mean kurtosis (MK), axial kurtosis (AK) and radial kurtosis (RK) were calculated. Tract-based spatial statistics （TBSS）analyses of WM tracts were performed with MK, MD, FA,AD,RD and RK in POCD patients and controls.POCD was observed in 19 patients (20.9%). The values of right superior longitudinal fasciculus(higher RD,lower MK,lower KA), left superior longitudinal fasciculus (lower MK,lower KA ), left anterior limb of internal capsule(higher MD, higher RD,lower MK), right anterior limb of internal capsule (lower MK,lower RK), left posterior limb of internal capsule(lower FA, higher MD,higher RD,lower MK,lower AK,lower RK ),right posterior limb of internal capsule(lower FA, higher MD,higher RD,lower MK,lower RK ),left retrolenticular part of internal capsule (lower MK,lower KA),right retrolenticular part of internal capsule(lower FA,higher RD,lower MK,lower RK), bilateral cerebral peduncle(lower FA), bilateral hippocampus cingulum(higher MD, higher RD) and bilateral sagittal stratum (higher RD,lower MK,lower KA) were significantly different in POCD patients from in controls (P<0.05, FWE corrected).

(1) the DKI parameters were sensitive to detect abnormality in white matter regions. Moreover, the MK decrease in POCD is predominantly driven by the AK decrease; in contrast, the FA decrease is mainly caused by the increase of RD. (2) DKI parameters (especially reduced DKI_FA) were mainly located in WM regions with fiber coherent; however, reduced DKI_MK were located mainly in white matter regions with fiber crossing; These findings suggest that the appropriate selection of DKI parameters would facilitate the detection of structural changes in of WM in POCD. (3) The changes of microstructure of superior longitudinal fasciculus, internal capsule, cerebral peduncle, hippocampus cingulum and sagittal stratum might involved in the onset and progression of POCD.

The changes of microstructure of superior longitudinal fasciculus, internal capsule, cerebral peduncle, hippocampus cingulum and sagittal stratum might be associated with POCD.