| Objective:To discuss the effect of magnetic resonance diffusion tensor imaging (DTI) on prefrontal cortex (PFC) and corpus callosum (CC) genu in the elderly with postoperative cognitive dysfunction (POCD).Methods:1. Sixty-five American Society of Anesthesiologists (ASA) class Ⅱ or Ⅲ patients aged at least65years undergoing elective gastrointestinal surgery were collected from Central South University Xiangya Medical School affiliated Haikou hospital between March1,2013and February28,2014. The patients with cognitive impairment according to a score on the mini-mental state examination (MMSE) had been excluded. The study received the hospital ethics committee approval and all patients gave written informed consent.2. All patients enrolled received MRI and DTI with cross-sectional scan preoperatively and on the7th day postoperatively by the same medical imaging expert who selected region of interest(ROI) with roughly similar position and size on the PFC and CC genu. The fractional anisotropy anisotropic (FA) value were acquired twice and took the average value.3. Cognitive function was assessed using neuropsychological testing preoperatively and on the7th day postoperatively by the same expert accepting special training and unaware of the patients’condition and MRI results. The evaluation was based on the following nine variables from the seven neuropsychological tests:Wechsler adult memory scale (WMS), Wechsler adult intelligence scale (WAIS), trail making test and the grooved pegboard test. The criteria was based on the Z score method recommended by the International Study of Postoperative Cognitive Dysfunction (ISPOCD).4. According to neuropsychological test results:Patients had cognitive dysfunction when two out of nine Z scores in individual tests or the combined Z score were1.96or more, otherwise the patient had no cognitive dysfunction. All the patients were divided into POCD and non-POCD groups.5. All the patients accepted combined inhalation and intravenous anesthesia and the bispectral index (BIS) value was maintained at45～60. The operation time and blood loss were recorded and all the patients received Patient-controlled Intravenous Analgesia (PCIA) postoperatively.6. SPSS statistics17.0was used for statistical analyses. The measurement data were presented as mean±standard deviation (x±s). If the data conforms to normal distribution and homogeneity of variance, parameter test will be adopted:paired t test in Comparison inner groups, two-sample t test in comparison between the two groups; Chi-squared test is adopted by enumeration data. A P value less than0.05was regarded as statistically significant difference.Results:1. The incidence of POCD:Six patients withdrew the research; POCD was found in17/59patients (28.81%) on the7th day postoperatively. The incidence of POCD in the elderly aged at least65years undergoing elective gastrointestinal surgery was28.81%on the7th day postoperatively.2. Cognitive function assessment results comparison:a) Comparison between groups preoperatively:there was no significant difference (P>0.05); b) Comparison inner groups:POCD group had significant difference in the visual reproduction, associative learning and the grooved pegboard test non-dominant hand (P<0.05), but the non-POCD group merely in the visual reproduction (P<0.05).3. Imaging results:a) Comparison between groups:the patients in POCD group had significantly lower FA value than non-POCD group in PFC and CC genu preoperatively and postoperatively(P<0.05); b) Comparison inner groups:No difference was found in the POCD and non-POCD group preoperatively and postoperatively (P>0.05).Conclusion:There is lower FA value on PFC and CC genu in POCD than non-POCD preoperatively, so FA value can contribute to preoperative prediction and evaluation of POCD in the elderly patients. |
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