A decrease in N-acetylaspartate and an increase in myoinositol in the anterior cingulate gyrus are associated with behavioral and psychological symptoms in Alzheimer's disease

BACKGROUND AND PURPOSE: The cognitive decline in Alzheimer's disease (AD) patients has been reported to involve alterations in the medial temporal lobe and the posterior cingulate gyrus. On the other hand, the neurochemical pathologies of the behavioral and psychological symptoms of dementia (BPSD) have not been sufficiently discussed. The aim of this study was to clarify the pathologies of BPSD in AD patients. METHODS: Thirty patients with probable AD were included and underwent the following assessments: Mini Mental State Examination (MMSE), Clock Drawing Test (CDT), Story Recall Test (SRT), Behavioral pathology in Alzheimer's disease (BEHAVE-AD) and proton MRS ((1)H-MRS). None of them had been medicated for BPSD. RESULTS: The MRS study revealed that MMSE, CDT, and SRT scores were positively related to N-acetyl-aspartate (NAA)/creatine(Cr) and negatively related to myoinositol (mI)/Cr in the posterior cingulate gyrus, but not in the anterior cingulate gyrus. On the other hand, the scores obtained in two categories of BEHAVE-AD (delusional thought/ activity disturbances) were negatively related with NAA/Cr and positively related with mI/Cr in the anterior cingulate gyrus, but not in the posterior cingulate gyrus. CONCLUSION: We conclude that BPSD and the decline in cognitive function in AD might have separate pathologies.     

Microstructural changes in the hippocampus and posterior cingulate in mild cognitive impairment and Alzheimer’s disease: a diffusion tensor imaging study

Diffusion tensor imaging (DTI) is a sensitive MRI technique in the detection of white matter degeneration. We sought to demonstrate microstructural changes in normal controls, patients with amnestic mild cognitive impairment (aMCI) and Alzheimer’s disease (AD) and to determine which DTI parameters could be a reliable tool for the early diagnosis of AD. In total, 90 participants (35 normal, 20 aMCI, 35 AD) were recruited. We included early AD patients with clinical dementia rating scores of 0.5 and 1. The fractional anisotropy and mean diffusivity values, DTI parameter, were measured with the regions of interest method in the bilateral hippocampal body and posterior cingulate. Clinical history, neurological examination, and neuropsychological assessments were conducted. The DTI parameters in the bilateral hippocampus and posterior cingulate in aMCI and AD were different from those in normal controls. No difference was found in DTI parameters of the posterior cingulate between aMCI and AD. However, hippocampal DTI parameters were different between aMCI and AD. Cognitive summary measures were significantly correlated with DTI parameters, especially FA values in the hippocampus. The DTI analysis technique demonstrated significant microstructural alterations in the hippocampus and posterior cingulate already in prodromal stage of AD. DTI parameters in the hippocampus may be a more sensitive method to determine microstructural changes in early AD states and more correlated with cognition than DTI parameters in the posterior cingulate.     

Cognitive impairment: classification by 1H magnetic resonance spectroscopy.

1H magnetic resonance spectroscopy (MRS) allows accurate and non-invasive in vivo metabolic study, and is a useful tool for the diagnosis of different forms of dementias. Cognitive impairment pathologies have been almost exclusively studied with MRS by comparison with healthy without a global comparison amongst Alzheimer disease (AD), vascular dementia, mild cognitive impairment (MCI) and major depression patients with cognitive impairment. Whereas decrease of N-acetylaspartate (NAA) and increase myo-Inositol (mI) at different brain locations by 1H MRS are common features of AD, Choline (Cho) alterations have been inconclusive. In our study, 64 patients with cognitive impairment were evaluated by 1H MRS using two echo times (31 and 136 ms). There were statistical differences between dementia (AD and vascular dementia) and non-dementia (MCI and depression) spectra at posterior cingulate gyrus. Cho/Cr, mI/Cr and NAA/Cr have been valuables for the differentiation amongst the different cognitive impairment entities. NAA/mI provides the best area under the ROC curve with the highest sensitivity (82.5%) and specificity (72.7%) in diagnosing AD. NAA/mI and mI/Cr ratios differed amongst the four cognitive impairment degenerative pathologies. Metabolic MRS differences found amongst patients with cognitive impairment entities can be useful to differentiate between AD, vascular dementia, MCI and depression.     

1H-MRS asymmetry changes in the anterior and posterior cingulate gyrus in patients with mild cognitive impairment and mild Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia worldwide. Amnestic mild cognitive impairment (aMCI) is often the prodromal stage to AD. Most patients with aMCI harbor the pathologic changes of AD and demonstrate transition to AD at a rate of 10%–15% per year. Patients with AD and aMCI experience progressive brain metabolite changes. Accumulating evidence indicates that the asymmetry changes of left and right brain happen in the early stage of AD. However, the features of asymmetry changes in both anterior cingulate gyrus (ACG) and posterior cingulate gyrus (PCG) are still unclear. Here, we examine the left–right asymmetry changes of metabolites in ACG and PCG. Fifteen cases of mild AD patients meeting criteria for probable AD of NINDS-ADRDA, thirteen cases of aMCI according to the Mayo Clinic Alzheimer's Disease Research Center criteria, and sixteen cases of age-matched normal controls (NC) received Proton magnetic resonance spectroscopy (¹H-MRS) for measurement of NAA/mI, NAA/Cr, Cho/Cr, and mI/Cr ratios in the PCG and ACG bilaterally. We analyzed ¹H-MRS data by paired t-test to validate the left–right asymmetry of ¹H-MRS data in the PCG and ACG. In AD, there was a significant difference in mI/Cr between the left and right ACG (P < 0.001) and the left and right PCG (P = 0.007). In aMCI, there was a significant difference in mI/Cr between the left and right ACG (P < 0.001). In NC, there were no differences in the ratio value of metabolites NAA/mI, NAA/Cr, Cho/Cr, and mI/Cr between the left and right ACG and PCG. Thus, the left–right asymmetry of mI/Cr in the ACG and PCG may be an important biological indicator of mild AD.     

Functional investigation of bilateral posterior cingulate gyri using multivoxel MR spectroscopy

The exact functional correlation of each hemisphere's posterior cingulate gyrus with the symptoms of Alzheimer's disease (AD) remains unknown. We attempted to evaluate the relationship between metabolite ratios in each hemisphere's posterior cingulate gyrus and cognitive deficits, using multivoxel magnetic resonance spectroscopy (MRS). We recruited 23 patients with AD, 16 patients with amnestic mild cognitive impairment and 22 cognitively normal subjects. All patients underwent multivoxel MRS in the bilateral posterior cingulate gyri. We statistically analyzed correlations between the N-acetylaspartate/creatine ratio (NAA/Cr) in each posterior cingulate gyrus and patients' raw scores on neuropsychological tests. The NAA/Cr of each posterior cingulate gyrus correlated well with the verbal learning test scores on immediate recall and delayed recall tasks. We found that the only cognitive domain to correlate with the NAA/Cr of each posterior cingulate gyrus was verbal memory. Our results did not show any significant functional difference between right and left posterior cingulate gyri.     

Evaluation of functional MRI markers in mild cognitive impairment

We aimed to investigate the use of advanced functional MRI (fMRI) techniques such as proton magnetic resonance spectroscopy (¹H-MRS) and the apparent diffusion coefficient (ADC) value in diffusion weighted imaging (DWI), in the diagnosis of mild cognitive impairment (MCI). Multiple indicators were combined in order to improve the early diagnostic value of MRS and ADC. We administered MRS and DWI-ADC to 13 patients with Alzheimer’s disease (AD), 9 patients with MCI, and 13 control patients. Changes in N-acetylaspartate/creatine and phosphocreatine (NAA/Cr), myoinositol/creatine (mI/Cr), and the ADC values in the hippocampus and the temporoparietal region were compared among groups. The sensitivity and specificity of different markers were analyzed individually and combined with others. All participants were evaluated by the mini mental state examination (MMSE), and the correlation between NAA/Cr, MI/Cr, ADC and the score of MMSE were analyzed separately. The NAA/Cr, mI/Cr and ADC values in the hippocampus among AD, MCI patients, and controls were significantly different (p < 0.05). At a fixed specificity of 84.6%, the high sensitivity of 100% and 92.9% in differentiating AD and MCI from normal controls were obtained by combining the three indicators. The receiver operating characteristic plots illustrated that the area under the multimarker curve was the biggest among the all four curves, and the sensitivity of the multimarkers was highest. The best correlation was obtained between ADC and MMSE, rather than between NAA or mI and MMSE. Thus, we found that changes in NAA/Cr, mI/Cr and ADC in the hippocampus and the temporoparietal regions were helpful in the clinical diagnosis of MCI. Furthermore, these changes showed potential in predicting the progression of MCI to AD if the multimarkers were combined.     

高血压病合并代谢异常患者脑磁共振波谱及弥散张量成像研究

目的 应用磁共振波谱（Magnetic Resonance Spectroscopy,MRS）及磁共振弥散张量成像（Diffusion Tensor Imaging,DTI）检测病程5年以上高血压病患者的脑内代谢物、脑部各向异性（fractional anisotropy,FA）值,以例早期发现亚临床脑细胞损害.方法 本研究分为病例组（高血压病12例）及对照组（17例健康体检者）,检查一般项目（身高、体重、血压、血糖、血脂、神经功能相关量表评分）,行头颅MRI、DWI、MRS、DTI检查,测定脑部背侧丘脑、扣带回后部、侧脑室后角NAA/Cr、Cho/Cr、NAA/Cho的比值及内囊后肢、放射冠区FA值.结果 （1）病例组NAA/Cr在背侧丘脑、扣带回后部、侧脑室后角均低于对照组（分别t=-2.405、-3.710、-2.068,P＜0.05）;NAA/Cho在扣带回后部、侧脑室后角均低于对照组（分别t=-4.347、3.578,P＜0.01）;Cho/Cr在扣带回后部高于对照组（t=2.965,P＜0.01）;（2）FA值在内囊后肢、放射冠区都明显低于对照组（t=-2.543、P＜0.05;t=-3.394、P＜0.01）.结论 高血压病合并代谢异常且病程5年以上者脑细胞代谢功能及神经纤维微结构已有损害,MRS、DTI检测有助于早期发现亚临床脑细胞损害.     

Abnormalities of magnetic resonance spectroscopy and diffusion tensor imaging are correlated with executive dysfunction in patients with ischemic leukoaraiosis

Abnormal diffusion tensor imaging (DTI) results have been observed in the periventricular white matter in patients with ischemic leukoaraiosis (ILA). However, the underlying pathological changes and their relationship to cognitive impairments are obscure. In addition, damage in the thalamus, an important structure in the executive function network, has been suggested in ILA, but is poorly understood. Twenty patients with ILA and 20 healthy volunteers with similar ages and educational histories underwent DTI, magnetic resonance spectroscopy (MRS) and a neuropsychological assessment. In patients with ILA, we observed an increased mean diffusivity (MD) and decreased levels of N-acetylaspartate (NAA)/creatine (Cr) in the anterior and posterior periventricular region and the thalamus, as well as decreased fractional anisotropy (FA) in the anterior and posterior periventricular regions. MD and NAA/Cr levels in the anterior and posterior periventricular white matter and NAA/Cr levels in the thalamus were correlated with executive function. DTI and MRS abnormalities were consistent with axonal and/or neuronal loss and dysfunction in the anterior and posterior periventricular white matter and the thalamus. This study demonstrates that DTI and MRS techniques can be used to investigate pathological changes in the anterior and posterior periventricular white matter and the thalamus; these changes may be correlated with executive functional changes in patients with ILA.     

Effects of Alzheimer disease on fronto-parietal brain N-acetyl aspartate and myo-inositol using magnetic resonance spectroscopic imaging

Previous magnetic resonance (MR) spectroscopy studies of Alzheimer disease (AD) reporting reduced N-acetyl aspartate (NAA) and increased myo-Inositol (mI) used single voxel techniques, which have limited ability to assess the regional distribution of the metabolite abnormalities. The objective of this study was to determine the regional distribution of NAA and mI alterations in AD by using MR spectroscopic imaging. Fourteen patients with AD and 22 cognitively normal elderly were studied using structural MR imaging and MR spectroscopic imaging. Changes of NAA, mI, and various metabolite ratios were measured in frontal and parietal lobe gray matter (GM) and white matter. This study found: (1) when compared with cognitively normal subjects, AD patients had increased mI and mI/creatine (Cr) ratios primarily in parietal lobe GM, whereas frontal lobe GM and white matter were spared; (2) in the same region where mI was increased, AD patients had also decreased NAA and NAA/Cr ratios, replicating previous findings; (3) however, increased mI or mI/Cr ratios did not correlate with decreased NAA or NAA/Cr ratios; and (4) using mI/Cr and NAA/Cr together improved sensitivity and specificity to AD from control as compared with NAA/Cr alone. In conclusion, decreased NAA and increased mI in AD are primarily localized in parietal lobe GM regions. However, the NAA and mI changes are not correlated with each other, suggesting that they represent different processes that might help staging of AD.     

Reproducibility of magnetic resonance spectroscopy in correlation with signal-to-noise ratio

An increased amount of myoinositol (mI) relative to creatine (Cr) by proton MR spectroscopy ((1)H-MRS) measurement gives a useful aid for the diagnosis of Alzheimer's disease (AD). Previous results of test-retest measurement of mI, however, have shown variability more than twice as large as for other metabolites. The aims of this study were to analyze test-retest variability of (1)H-MRS measurements in correlation with signal-to-noise ratio (SNR). Ten subjects clinically suspected of mild AD were examined twice (2-14 days apart) with (1)H-MRS measurements of voxels placed at anterior and posterior cingulate cortex. The percent differences between two measurements (%differences) of mI/Cr showed a significant linear trend to decrease as average SNR increased, but %differences of N-acetylaspartate (NAA)/Cr and choline (Cho)/Cr did not. The average of %differences was 10.5, 15.0 and 20.8 for NAA/Cr, Cho/Cr, and mI/Cr, respectively, indicating a prominent deterioration of mI/Cr measurement reproducibility, which decreased to 6.96, 15.4 and 9.87, respectively, when the analysis was limited to measurements with SNR over 25. The results indicate that MRS measurements with high SNR should be used to obtain reliable assessments of mI/Cr as accurate diagnostic indicator of AD in clinical MR examinations.     

1H-MRS evaluation of metabolism in Alzheimer's disease and vascular dementia

Proton magnetic resonance spectroscopy (1H-MRS) allows major metabolites to be measured noninvasively in defined regions of the living brain, and can detect biochemical abnormalities where conventional structural imaging appears normal. MRS can be performed in 10 min as part of a clinical MRI examination. Biochemical abnormalities in Alzheimer's Disease (AD), vascular dementia (VaD) and other primary degenerative dementias have been investigated using MRS. Characteristic and consistent abnormalities in AD are decreased N-acetyl aspartate (NAA) and elevated myo-inositol (mI) in the mesial temporal and parieto-occipital cortex. These are thought to represent neuronal loss/dysfunction and gliosis, in anatomic distributions which reflect early pathological involvement and atrophy patterns in AD. Less consistent disturbances of glutamine and glutamate (Glx) and choline-containing compounds (Cho) have also been reported. Similar changes are seen in VaD; mostly in white matter, whereas in AD they predominate in cortical grey matter. The regional distribution of grey matter involvement may differ between AD and other degenerative dementias. Hence, both the nature and anatomic distribution of metabolite abnormalities contribute to diagnostic discrimination with MRS. NAA/mI ratios from short echo time spectra of the posterior cingulate region cortex discriminate reliably between AD subjects, normal individuals and those with VaD, and provides a useful clinical test, as an adjunct to structural imaging. Elevated mI is detected in mild cognitive impairment (MCI) and quantitative metabolite measures correlate with degrees of cognitive impairment in AD; these suggest a possible role for MRS in early diagnosis and for surrogate biochemical markers for monitoring disease progression and therapeutic response.     

Comparative diagnostic utility of different MR modalities in mild cognitive impairment and Alzheimer's disease

This study compares the diagnostic accuracy of magnetic resonance (MR)-based hippocampal volumetry, single voxel (1)H MR spectroscopy ((1)H MRS) and MR diffusion-weighted imaging (DWI) measurements in discriminating patients with amnestic mild cognitive impairment (MCI), Alzheimer's disease (AD) and normally aging elderly. Sixty-one normally aging elderly, 24 MCI and 22 AD patients underwent MR-based hippocampal volumetry, (1)H MRS and DWI. (1)H MRS voxels were placed over both of the posterior cingulate gyri, and N-acetyl aspartate (NAA)/creatine (Cr), myoinositol (MI)/Cr and NAA/MI ratios were obtained. Apparent diffusion coefficient (ADC) maps were derived from DWI, and hippocampal borders were traced to measure hippocampal ADC. At 80% specificity, the most sensitive single measurement to discriminate MCI (79%) and AD (86%) from controls was hippocampal volumes. The most sensitive single measurement to discriminate AD from MCI was posterior cingulate gyrus NAA/Cr (67%). At high specificity (>85-90%), combinations of MR measures had superior diagnostic sensitivity compared with any single MR measurement for the AD vs. control and control vs. MCI comparisons. The MR measures that best discriminate more from less affected individuals along the cognitive continuum from normal to AD vary with disease severity. Selection of imaging measures used for clinical assessment or monitoring efficiency of therapeutic intervention should be tailored to the clinical stage of the disease.     

Brain metabolism differs in Alzheimer's disease and Parkinson's disease dementia

BackgroundFew comparative studies exist of metabolic brain changes among neurodegenerative illnesses. We compared brain metabolic abnormalities in Alzheimer's disease (AD) and in Parkinson's disease with dementia (PDD) as measured by proton magnetic resonance spectroscopy (MRS).MethodsTwelve patients with idiopathic PDD, 22 patients with probable mild AD, and 61 healthy older controls underwent posterior cingulate MRS.ResultsPatients with AD exhibited reduced N-acetyl aspartate (NAA)/creatine (Cr) (P < .05) and increased choline (Cho)/Cr (P < .05) and myo-inositol (mI)/Cr (P < .01) compared with controls. Patients with PDD exhibited reduced NAA/Cr (P < .05) and glutamate (Glu)/Cr (P < .01) compared with controls. There was reduced Glu/Cr in PDD compared with AD (P < .01).ConclusionsPatients with AD and patients with PDD exhibited distinct brain metabolic MRS profiles. Findings suggest that comparison of brain MRS profiles across dementias provides useful direction for future study.     

Regional metabolic patterns in mild cognitive impairment and Alzheimer's disease: A 1H MRS study

BACKGROUND: Mild cognitive impairment (MCI) is a recently described transitional clinical state between normal aging and AD. Assuming that amnestic MCI patients had pathologic changes corresponding to an early phase and probable AD patients to a later phase of the disease progression, the authors could approximate the temporal course of proton MR spectroscopic (1H MRS) alterations in AD with a cross-sectional sampling scheme. METHODS: The authors compared 1H MRS findings in the superior temporal lobe, posterior cingulate gyri, and medial occipital lobe in 21 patients with MCI, 21 patients with probable AD, and 63 elderly controls. These areas are known to be involved at different neurofibrillary pathologic stages of AD. RESULTS: The N-acetylaspartate (NAA)/creatine (Cr) ratios were significantly lower in AD patients compared to both MCI and normal control subjects in the left superior temporal and the posterior cingulate volumes of interest (VOI) and there were no between-group differences in the medial occipital VOI. Myoinositol (MI)/Cr ratios measured from the posterior cingulate VOI were significantly higher in both MCI and AD patients than controls. The choline (Cho)/Cr ratios measured from the posterior cingulate VOI were higher in AD patients compared to both MCI and control subjects. CONCLUSION: These findings suggest that the initial 1H MRS change in the pathologic progression of AD is an increase in MI/Cr. A decrease in NAA/Cr and an increase in Cho/Cr develop later in the disease course.     

Diffusion tensor imaging measures of normal appearing white matter in patients who are aging,or have amnestic mild cognitive impairment,or Alzheimer’s disease

To evaluate whether cerebral white matter integrity is related to cognitive function, and whether diffusion tensor imaging (DTI) could differentiate amnestic mild cognitive impairment (aMCI) from Alzheimer’s disease (AD), 12 patients with AD, 12 with aMCI, and 12 controls were recruited for this study. Cognitive functions of all subjects were assessed using the Mini-Mental State Examination (MMSE) and AD Assessment Scale – Cognitive Subscale (ADAS-Cog). DTI studies were acquired, and fractional anisotropy (FA) and mean diffusivity (MD) values of normal-appearing white matter (NAWM) in multiple brain regions were obtained. Results showed that MMSE and ADAS-Cog subscores were significantly associated with white matter integrity of the temporal-parietal lobes. A decrease in FA values and an increase in MD values in multiple cortical regions were confirmed in patients with AD compared to controls. MD values in the posterior region of the corpus callosum in aMCI differed from those of early AD. Significant reductions of FA values in the NAWM of the parietal lobe was observed in aMCI compared to controls. Our data indicate that the microstructural white matter integrity in the temporal-parietal lobes is gradually impaired in the progressive process of AD, and that splenium MD values could be used as a biomarker differentiating aMCI from AD.     

氢质子磁共振波谱对Alzheimer病神经生化改变的分析

目的研究Alzheimer病(Alzheimerdisease,AD)的氢质子磁共振波谱分析改变,并与认知正常的老年志愿者(normalcognition,NC)进行比较。方法对AD组21例及NC组20名被观察者行磁共振波谱分析,测定双侧海马、颞顶叶联合区的N乙酰天门冬氨酸(N acetylaspartate,NAA)、胆碱(choline,Cho)和肌醇(myo inositol,mI)与肌酸(creatine,Cr)的比值。采用SPSS11.5软件进行统计分析。结果AD组和NC组双侧海马和颞顶联合区的NAA/Cr差异有显著性(P<0.05),双侧海马和左侧颞顶叶联合区的mI/Cr差异有显著性(P<0.05),双侧海马和颞顶叶联合区的Cho/Cr差异无显著性(P<0.05)。只有左侧海马的NAA/Cr水平下降与AD的严重程度呈正相关(r=0.470,P<0.05)。结论磁共振波谱分析可发现AD海马及颞顶联合区的NAA/Cr、mI/Cr改变,左侧海马NAA/Cr的减低可帮助评价AD的严重程度。     

弥散张量成像技术预测遗忘型轻度认知障碍患者向老年性痴呆转化的随访研究

目的:探讨弥散张量成像技术(diffusion tensor imaging,DTI)对遗忘型轻度认知功能障碍(aMCI)向老年性痴呆(AD)转化的预测作用。方法:41例aMCI患者(aMCI组)常规予核磁共振(MRI)和DTI扫描,测定感兴趣区的各向异性分数(fractional anisotropy,FA)和表观扩散系数(apparent diffusion coefficient,ADC),以20名老年健康志愿者作为对照(正常对照组)并随访1~3年。结果:与正常对照组比较,aMCI组41例患者中有22例扣带束FA基线值偏低(P0.05),随访1~3年后,其中有19例转化为AD;另外19例扣带束FA值正常的aMCI患者只有2例转化为AD。与非转化AD者比较,AD转化者前额叶、颞叶、海马、下额枕束、胼胝体膝部和扣带束等部位FA值降低(P均0.01),颞叶、海马等部位ADC值升高(P均0.05)。结论:DTI技术具有预测aMCI向AD转化的作用,aMCI患者扣带束FA值低可能是aMCI向AD转化的敏感指标。     

多模态影像技术在胶质瘤复发与放射性坏死鉴别诊断中的价值

目的 探讨多模态影像技术在脑胶质瘤复发和放射性坏死鉴别诊断中的应用价值。方法 回顾性分析2016年6月至2021年12月手术治疗并经术后病理检查确诊的45例胶质瘤的临床资料。以二次手术或穿刺活检病理检查结果作为诊断胶质瘤复发和放射性坏死的金标准。术后3~6个月，灌注加权成像（PWI）检测相对脑血容量（rCBV），弥散成像（DWI）检测表观弥散系数（ADC），磁共振波谱（MRS）检测N-乙酰天门冬氨酸（NAA）、胆碱（Cho）、肌酸（Cr）等参数并计算Cho/NAA、Cho/Cr比值，PET-CT检测标准摄取值（SUV）。结果 45例中，胶质瘤复发34例（复发组），放射性坏死11例（坏死组）。复发组rCBV、SUV、Cho/NAA值明显大于坏死组（P<0.05），而ADC值明显小于坏死组（P<0.05）；两组Cho/Cr值无统计学差异（P>0.05）。ROC曲线分析显示，rCBV、ADC、Cho/NAA、Cho/Cr、SUV均具有鉴别价值，其中rCBV效果最佳（P<0.05）；而Cho/Cr无明显鉴别意义（P>0.05）。rCBV、ADC、Cho/NAA、Cho/Cr、SUV联合鉴别的敏感度、特异度分别为99%和100%，明显优于单一指标（P<0.01）。结论单纯应用MRI或PET-CT某一序列或单一检查手段鉴别胶质瘤复发与放射性坏死具有一定局限性，联合应用PWI、DWI、MRS、PET-CT，可显著提高鉴别诊断准确率，对制定个体化治疗方案具有重要临床意义。     

Advances in longitudinal studies of amnestic mild cognitive impairment and Alzheimer’s disease based on multi-modal MRI techniques

Amnestic mild cognitive impairment (aMCI) is a prodromal stage of Alzheimer’s disease (AD), and 75%–80% of aMCI patients finally develop AD. So, early identification of patients with aMCI or AD is of great significance for prevention and intervention. According to cross-sectional studies, it is known that the hippocampus, posterior cingulate cortex, and corpus callosum are key areas in studies based on structural MRI (sMRI), functional MRI (fMRI), and diffusion tensor imaging (DTI) respectively. Recently, longitudinal studies using each MRI modality have demonstrated that the neuroimaging abnormalities generally involve the posterior brain regions at the very beginning and then gradually affect the anterior areas during the progression of aMCI to AD. However, it is not known whether follow-up studies based on multi-modal neuroimaging techniques (e.g., sMRI, fMRI, and DTI) can help build effective MRI models that can be directly applied to the screening and diagnosis of aMCI and AD. Thus, in the future, large-scale multi-center follow-up studies are urgently needed, not only to build an MRI diagnostic model that can be used on a single person, but also to evaluate the variability and stability of the model in the general population. In this review, we present longitudinal studies using each MRI modality separately, and then discuss the future directions in this field.     

Cortical brain metabolism as measured by proton spectroscopy is related to memory performance in patients with amnestic mild cognitive impairment and Alzheimer's disease

AIMS: To investigate the relationship between verbal memory performance and brain metabolism as determined by proton spectroscopy ((1)H-MRS) in selected cortical brain regions. To characterize metabolite abnormalities across the continuum of degenerative disease from mild impairment to dementia. METHODS: 27 controls, 27 amnestic mild cognitive impairment (aMCI) patients and 35 Alzheimer's disease (AD) patients. Verbal memory was assessed with the Text Memory Test, the Wordlist Learning Test (WL-Learning Test), and with a memory screening test, the Memory Alteration Test (M@T). Single-voxel (1)H-MRS was obtained in the posterior cingulate (P-CING), left temporal pole (L-TPOLE) and left posterior temporoparietal region (L-TPAR). RESULTS: WL-Learning Test scores were inversely associated with myoinositol/creatine ratios (mI/Cr) in the L-TPAR (r = -0.404, p < 0.002). Negative associations were also observed between M@T global scores and mI/Cr in the P-CING (r = -0.42; p < 0.001), L-TPOLE (r = -0.34; p < 0.005) and L-TPAR (r = -0.46; p < 0.001). A positive association was found between M@T scores and N-acetylaspartate concentrations in the P-CING (r = 0.33; p < 0.003). CONCLUSION: Verbal learning performance is related to metabolic changes in cortical brain regions known to be involved in the neurodegenerative process of aMCI and AD.