| Objective:To evaluate the predict value of'H-MRS of the medial temporal lobe in the elderly who will suffer from postoperative cognitive dysfunction.Methods:Forty-eight ASA physical statusⅡ-Ⅲpatients aged over 65 years were studied after elective abdominal surgery under general anesthesia, all patients were accepte neuropsychological tests in 1 day before and 7days after surgery, The test battery included sensitive tests from the Wechsler Adult Memory Scale and Wechsler Adult Intelligence Scale, Trail Making Test(Part A)and the Grooved Pegboard Test. An SD unit for each test wascalculated from the healthy first scores. For patients, We compared changes in performance for each test from baseline(first session)to 7days after surgery, and divided the result by the control-group SD to obtain a Z score for each test. Large positive Z scores showed a deterioration in cognitive function. We defined a composite z score from all of the Z scores. Patients had cognitive dysfunction when two Z scores in individual tests or the combined Z score were 1.96 or more. Then, we assigned all patients to POCD group (A group)or non-POCD group(B group) according tothe results of neuropsychological tests. Single-voxel 1H-MRS of STEAM sequences(TR 1,500ms, TE 135ms) at 1.5T superconducting MRI were carried out in the the medial temporal lobe of each individual in 1 day before and 7days after surgery. After the scan was completed, spectral curve,N-acetyl aspartate (NAA),choline (Cho),creatine (Cr) and the integral value were displayed in the screen. The ratios of NAA/Cr and Cho/Cr were compared statistically between the two groups.Results:Forty-eight patients participated in the whole process of this study and we found cognitive dysfunction in 14(29.2%)of patients in 7days after surgery.the NAA/Cr of the medial temporal lobe between the elderly of POCD and non-POCD group were signifinantly diffenrence(P <0.05) before and after operation, that is to say,NAA/Cr ratios were lower in the left ((preoperative:NAA/Cr 1.43±0.18<1.72±0.29, postoperative:left NAA/Cr 1.41±0.20<1.69±0.27) and right (preoperative:NAA/Cr 1.40±0.21<1.68±0.27, postoperative NAA/Cr 1.42±0.17<1.63±0.25) medial temporal lobe of POCD subjects, while the Cho/Cr between the two groups no significant difference (P> 0.05).the NAA/Cr,Cho/Cr ratio of the left medial temporal lobe were no signifinantly diffenrence compared with the right in POCD or non-POCD groups. Similarly,in before and after surgery,no significant difference in in the ratio of NAA/Cr,Cho/Cr was observed in POCD group or non-POCD groups (P> 0.05).Conclusions:The incidence of POCD in the elderly was 29.2% in the study. In POCD group,a remarkable decrease in the ratio of NAA /Cr of the medial temporal lobe was observed.1H-MRS can provide non-invasive brain metabolism in the elderly with POCD, especially, the ratio of NAA/Cr is beneficial for prediction of POCD.
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