轻度认知功能障碍与脑白质弥散张量成像的相关性研究

目的通过磁共振弥散张量成像研究不同区域脑白质损害与轻度认知功能(MCI)的关系。方法纳入2015年7月至2016年2月我院的住院患者56例为研究对象,其中MCI组34例,认知功能正常组22例。所有研究对象进行一般情况检查,完成神经心理学量表检测。通过头颅磁共振弥散张量成像(DTI)检查对不同脑区白质纤维进行部分各向异性(FA)值测量。结果 MCI组患者与认知功能正常组相比,右侧额叶FA值(0.335±0.068)、左侧颞叶白质FA值(0.391±0.032)及胼胝体膝部FA值(0.658±0.053)降低,差异具有统计学意义(P0.05)。将上述FA值和MMSE、Mo CA量表中各认知域进行典型相关分析,结果显示右侧额叶白质FA值与注意与计算力呈正相关,左侧颞叶白质和胼胝体膝部FA值与记忆力呈正相关(P0.05)。结论 MCI患者注意与计算力的障碍可能与右侧额叶白质损害有关,而左侧颞叶白质及胼胝体膝部白质的损害可能导致早期的记忆障碍。DTI可能成为超早期识别与诊断MCI的新方法。     

Diffusion tensor imaging in early Alzheimer's disease

Our aim was to investigate the extent of white matter tissue damage in patients with early Alzheimer disease (AD) using diffusion tensor magnetic resonance imaging (DTI). Although AD pathology mainly affects cortical grey matter, previous magnetic resonance imaging (MRI) studies showed that changes also exist in the white matter (WM). However, the nature of AD-associated WM damage is still unclear. Conventional and DTI examinations (b=1000 s/mm(2), 25 directions) were obtained from 12 patients with early AD (Mini Mental State Examination [MMSE] score=27, Grober and Buschke test score=33.2, digit span score=5.6) and 12 sex- and age-matched volunteers. The right and left mean diffusivity (MD) and fractional anisotropy (FA) of several WM regions were pooled in each patient and control, and compared between the two groups. Volumes of the whole brain and degree of atrophy of the temporal lobe were compared between the two groups. In AD, MD was increased in the splenium of the corpus callosum and in the WM in the frontal and parietal lobes. FA was bilaterally decreased in the WM of the temporal lobe, the frontal lobe and the splenium compared with corresponding regions in controls. Values in other areas (occipital area, superior temporal area, cingulum, internal capsule, and genu of the corpus callosum) were not different between patients and controls. No correlations were found between the MMSE score and the anisotropy indices. Findings of DTI reveal abnormalities in the frontal and temporal WM in early AD patients. These changes are compatible with early temporal-to-frontal disconnections.     

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.     

阿尔茨海默病与轻度认知障碍弥散张量成像研究

目的:应用磁共振弥散张量成像技术(DTI)研究阿尔茨海默病(AD)与轻度认知障碍患者(MCI)脑白质损伤情况。方法:对21例AD患者、15例MCI患者和20名健康志愿者进行脑部DTI扫描后,测量双脑区感兴趣区的各向异性分数值(FA)且进行比较。结果:AD患者额叶、顶叶、颞叶和胼胝体的FA值与MCI组和对照组均存在显著性差异,MCI患者仅颞叶和胼胝体的FA值与对照组均存在显著性差异。结论:AD患者与MCI患者存在脑白质结构的差异,DTI技术能够在一定程度上提供MCI的早期诊断指标。     

Regional networks underlying interhemispheric connectivity: an EEG and DTI study in healthy ageing and amnestic mild cognitive impairment

Interhemispheric coherence derived from electroencephalogram (EEG) recordings is a measure of functional interhemispheric connectivity. Diffusion tensor imaging (DTI) determines the integrity of subcortical fiber tracts. We studied the pattern of subcortical fiber tracts underlying interhemispheric coherence and its alteration in 16 subjects with amnestic mild cognitive impairment (MCI), an at risk syndrome for Alzheimer's disease, and 20 cognitively healthy elderly control subjects using resting state EEG and high resolution DTI at 3 T. We used a multivariate network approach based on principal component analysis to determine effects of coherence on the regional pattern of diffusivity. Temporo-parietal coherence in the alpha band was significantly correlated with diffusivity in predominantly posterior white matter tracts including posterior corpus callosum, parietal, temporal and occipital lobe white matter, thalamus, midbrain, pons, and cerebellum, both in MCI subjects and controls (P < 0.05). In MCI subjects, frontal coherence in the alpha band was significantly correlated with a predominately frontal pattern of diffusivity including fiber tracts of the anterior corpus callosum, frontal lobe white matter, thalamus, pons, and cerebellum (P < 0.05). The study provides a methodology to access specific networks of subcortical fiber tracts subserving the maintenance of interhemispheric resting state coherence in the human brain.     

弥散张量成像对阿尔茨海默病脑白质改变的评价

目的分析阿尔茨海默病(Alzheimer's disease,AD)脑白质结构改变及与认知功能的关系。方法对37例AD组和32例对照组行简易精神状态量表(mini-mental State examinationn,MMSE)评估和DTI扫描。采用基于全脑体素分析法对两组全脑白质各向异性(fractional anisotropy,FA)图进行比较,采用t检验分析FA值差异,并评估AD组MMSE评分与FA值相关性。结果 AD患者出现FA值下降区域广泛分布在右侧额叶、颞叶、枕叶、丘脑及双侧扣带回、胼胝体、楔前叶、顶叶下回、顶下小叶、缘上回及海马旁回(其中P0.001,未经校正的P值);当使用经FWE校正的P0.05后,AD患者右侧扣带回、左侧胼胝体、颞叶下回及双侧顶叶下回、额叶下回、楔前叶区域FA值较对照组显著下降。AD患者FA值下降与MMSE量表评分呈正相关,(P0.001,未经校正)。结论 AD患者存在特定脑区白质结构改变,并与认知功能损害程度呈正相关。     

Ultrastructural hippocampal and white matter alterations in mild cognitive impairment: a diffusion tensor imaging study

Mild cognitive impairment (MCI) is considered to be a transitional stage between normal aging and dementia. In Alzheimer's disease (AD), white matter structural pathology is due to Wallerian degeneration and central angiopathy. However, in MCI patients, the presence and extent of white matter alterations as a possible correlate of impaired memory function and as predictor of subsequent progression to AD is not clarified yet. Diffusion tensor imaging (DTI) reveals the ultrastructural integrity of cerebral white matter tracts. Therefore, it could detect pathological processes that modify tissue integrity in patients with MCI. In our prospective study, conventional and diffusion tensor MR scans were obtained from 14 patients with MCI, 19 patients with AD, and 10 healthy controls. Mean diffusivity (MD) and fractional anisotropy (FA) were measured in temporal, frontal, parietal and occipital white matter regions as well as in the corpus callosum (genu and splenium) and the hippocampus. MCI patients showed higher MD values in the left centrum semiovale (p = 0.013; right: p = 0.026), in the left temporal (p = 0.006), the right temporal (p = 0.014) and the left hippocampal (p = 0.002) region as compared to the control group. FA values of MCI patients and controls did not differ significantly in any region. Compared to controls, AD patients had increased MD values in the left centrum semiovale (p = 0.012), the left parietal (p = 0.001), the right parietal (p = 0.028), the left temporal (p = 0.018), the right temporal (p = 0.011) and the left hippocampal region (p = 0.002). Decreased FA values were measured in the left temporal area (p = 0.017) and in the left hippocampus (p = 0.031) in AD patients compared to controls. FA and MD values did not differ significantly between AD and MCI patients. Elevated MD values indicating brain tissue alterations in MCI patients were found in regions that are typically involved in early changes due to AD, particularly the left hippocampus. The sensitivity of distinguishing MCI patients from controls was 71.4% (with a specificity set at 80%). Therefore, the DTI technique validates the MCI concept, and diffusion tensor MR measurement can be a helpful tool to quantify MCI pathology in vivo.     

In vivo demonstration of microstructural brain pathology in progressive supranuclear palsy: A DTI study using TBSS

We investigated DTI changes, potentially indicating alterations of microstructure and brain tissue integrity in 13 patients with probable progressive supranuclear palsy (PSP, Richardson syndrome) at stage III or less and 10 age‐matched controls using a whole brain analysis of diffusion tensor imaging (DTI) data. DTI images were analyzed using tract‐based spatial statistics, a hypothesis‐free technique. Fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD) were determined. In patients with PSP, significant increases in FA (P < 0.0001), an unspecific measure of microstructural tissue integrity, were found in the cerebellum and in the superior cerebellar peduncle bilaterally, in the fornix, the body of the corpus callosum and the olfactory region, when compared with age‐matched healthy controls. Further, regional reductions in AD (P < 0.0001), an indicator of altered axonal integrity, were observed in the pons, the right substantia nigra and the cerebellar white matter bilaterally. Significant increases in RD (P < 0.0001), a potential measure of altered myelin integrity, occurred bilaterally in the superior cerebellar peduncle, the cerebellar white matter, the vermis of the cerebellum, the fornix, the body of the corpus callosum, and the olfactory region. RD values in the superior cerebellar peduncle discriminated patients with PSP and controls with high sensitivity (0.92) and specificity (1.0). The findings are supported by neuropathological studies. Our data suggest the usefulness of this clinically available new technique as a possible tool for differential diagnosis. © 2010 Movement Disorder Society     

Posterior cingulum white matter disruption and its associations with verbal memory and stroke risk in mild cognitive impairment

Medial temporal lobe and temporoparietal brain regions are among the earliest neocortical sites to undergo pathophysiologic alterations in Alzheimer's disease (AD), although the underlying white matter changes in these regions is less well known. We employed diffusion tensor imaging to evaluate early alterations in regional white matter integrity in participants diagnosed with mild cognitive impairment (MCI). The following regions of interests (ROIs) were examined: 1) anterior cingulum (AC); 2) posterior cingulum (PC); 3) genu of the corpus callosum; 4) splenium of the corpus callosum; and 5) as a control site for comparison, posterior limb of the internal capsule. Forty nondemented participants were divided into demographically-similar groups based on cognitive status (MCI: n = 20; normal control: n = 20), and fractional anisotropy (FA) estimates of each ROI were obtained. MCI participants showed greater posterior white matter (i.e., PC, splenium) but not anterior white matter (i.e., AC, genu) changes, after adjusting for age, stroke risk, and whole brain volume. FA differences of the posterior white matter were best accounted for by changes in radial but not axial diffusivity. PC FA was also significantly positively correlated with hippocampal volume as well as with performance on tests of verbal memory, whereas stroke risk was significantly correlated with genu FA and was unrelated to PC FA. When investigating subtypes of our MCI population, amnestic MCI participants showed lower PC white matter integrity relative to those with non-amnestic MCI. Findings implicate involvement of posterior microstructural white matter degeneration in the development of MCI-related cognitive changes and suggest that reduced FA of the PC may be a candidate neuroimaging marker of AD risk.     

The impact of human immune deficiency virus and hepatitis C coinfection on white matter microstructural integrity

The purpose of the present study is to examine the integrity of white matter microstructure among individuals coinfected with HIV and HCV using diffusion tensor imaging (DTI). Twenty-five HIV+ patients, 21 HIV+/HCV+ patients, and 25 HIV? controls were included in this study. All HIV+ individuals were stable on combination antiretroviral therapy (cART; ≥3 months). All participants completed MRI and neuropsychological measures. Clinical variables including liver function, HIV-viral load, and CD4 count were collected from the patient groups. DTI metrics including mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD), and fractional anisotropy (FA) from five subregions of the corpus callosum were compared across groups. The HIV+/HCV+ group and HIV+ group were similar in terms of HIV clinical variables. None of the participants met criteria for cirrhosis or fibrosis. Within the anterior corpus callosum, significant differences were observed between both HIV+ groups compared to HIV? controls on DTI measures. HIV+ and HIV+/HCV+ groups had significantly lower FA values and higher MD and RD values compared to HIV? controls; however, no differences were present between the HIV+ and HIV+/HCV+ groups. Duration of HIV infection was significantly related to DTI metrics in total corpus callosum FA only, but not other markers of HIV disease burden or neurocognitive function. Both HIV+ and HIV+/HCV+ individuals had significant alterations in white matter integrity within the corpus callosum; however, there was no evidence for an additive effect of HCV coinfection. The association between DTI metrics and duration of HIV infection suggests that HIV may continue to negatively impact white matter integrity even in well-controlled disease.     

Cerebral small vessel disease affects white matter microstructure in mild cognitive impairment

Microstructural white matter deterioration is a frequent finding in mild cognitive impairment (MCI), potentially underlying default mode network (DMN) dysfunctioning. Thus far, microstructural damage in MCI has been attributed to Alzheimer's disease pathophysiology. A cerebrovascular role, in particular the role of cerebral small vessel disease (CSVD), received less interest. Here, we used diffusion tensor imaging (DTI) to examine the role of CSVD in microstructural deterioration within the normal appearing white matter (NAWM) in MCI. MCI patients were subdivided into those with (n = 20) and without (n = 31) macrostructural CSVD evidence on MRI. Using TBSS we performed microstructural integrity comparisons within the whole brain NAWM. Secondly, we segmented white matter tracts interconnecting DMN brain regions by means of automated tractography segmentation. We used NAWM DTI measures from these tracts as dependent variables in a stepwise‐linear regression analysis, with structural and demographical predictors. Our results indicated microstructural deterioration within the anterior corpus callosum, internal and external capsule and periventricular white matter in MCI patients with CSVD, while in MCI patients without CSVD, deterioration was restricted to the right perforant path, a tract along the hippocampus. Within the full cohort of MCI patients, microstructure within the NAWM of the DMN fiber tracts was affected by the presence of CSVD. Within the cingulum along the hippocampal cortex we found a relationship between microstructural integrity and ipsilateral hippocampal volume and the extent of white matter hyperintensity. In conclusion, we found evidence of CSVD‐related microstructural damage in fiber tracts subserving the DMN in MCI. Hum Brain Mapp 35:2836–2851, 2014. © 2013 Wiley Periodicals, Inc .     

Altered white matter integrity in temporal lobe epilepsy: Association with cognitive and clinical profiles

Purpose: Diffusion tensor imaging (DTI) studies have reported substantial white matter abnormalities in patients with temporal lobe epilepsy (TLE). However, limited data exist regarding the extent of white matter tract abnormalities, cognitive effects of these abnormalities, and relationship to clinical factors. The current study examined these issues in subjects with chronic TLE. Methods: DTI data were obtained in 12 TLE subjects and 10 age‐matched healthy controls. Voxel‐wise statistical analysis of fractional anisotropy (FA) was carried out using tract‐based spatial statistics (TBSS). White matter integrity was correlated with cognitive performance and epilepsy‐related clinical parameters. Results: Subjects with TLE, as compared to healthy controls, demonstrated four clusters of reduced FA, in anterior temporal lobe, mesial temporal lobe, and cerebellum ipsilateral, as well as frontoparietal lobe contralateral to the side of seizure onset. Mean FA was positively correlated with delayed memory, in anterior temporal lobe; and immediate memory, in mesial temporal lobe. Lower FA values in the posterior region of corpus callosum were related to earlier age of seizure onset. Conclusion: TLE is associated with widespread disturbances in white matter tracts and these changes have important cognitive and clinical consequences.     

White matter magnetic resonance imaging hyperintensity in Alzheimer's disease: correlations with corpus callosum atrophy

We have previously demonstrated with MRI that as well as marked white matter involvement in late-onset Alzheimer's disease (AD), atrophy of the corpus callosum may also be present. This finding prompted us to study possible correlations between atrophy of the corpus callosum and white matter hyperintensity (WMH) and between white matter lesions and the severity of the disease. We compared the corpus callosum and white matter lesions on MRI from 15 AD patients and 15 controls. The white matter lesions were scored according to the Scheltens' rating scale. We found a significant reduction of the area of the corpus callosum and more severe white matter lesions in AD patients than in controls. Both atrophy of the corpus callosum and the severity of lesions depended mainly on the diagnosis of senile dementia of the Alzheimer type and on age but not on the diagnosis of presenile AD. We demonstrated a negative correlation between white matter lesions scores and areas of corpus callosum in AD patients and no correlation between the white matter lesions and the severity of the disease. We demonstrated that white matter lesions including WMH and atrophy of the corpus callosum are more frequent in AD than in controls. The predominance of white matter lesions in senile AD may be explained by the combination of aging and disease processes.     

弥漫性轴索损伤早期磁共振弥散张量成像检测与恢复期注意力障碍的相关性研究

目的应用磁共振弥散张量成像技术研究患者早期弥漫性轴索损伤(DAI)与恢复期时注意力障碍之间的关系。方法分别对12例DAI患者(伤后4.1±1.7d)和10例健康志愿者(正常对照组)进行MRI弥散张量成像(DTI)检查及神经心理测评量表评估。使用感兴趣区域方法对两组DTI图像的下纵束、上纵束、胼胝体膝部和胼胝体压部的FA值进行比较;分别对恢复期的DAI患者(20.9±7.3 M)与健康志愿者行认知量表评估,并对DAI组的FA值与神经心理测评量表的总分行pearson直线相关分析。结果与健康对照组相比,DAI患者全部感兴趣区的FA值显著降低(P<0.05)、注意力功能显著降低(P<0.05)。DAI患者中的上纵束和下纵束与注意力量表总分呈负性相关(P<0.05),胼胝体膝部和胼胝体压部与注意力量表总分无相关性(P>0.05)。结论利用DTI技术检测早期白质纤维束的损伤可以预测DAI患者在恢复期中的注意力功能障碍,为临床上DAI患者的认知障碍的诊断提供一定的科学依据。     

Executive dysfunction and periventricular diffusion tensor changes in amnesic mild cognitive impairment and early Alzheimer's disease

Our aim in this study was to explore the neural substrates of executive function in frontal and nonfrontal white matter using diffusion tensor imaging (DTI). We studied the relationship between executive dysfunction and DTI measurements on 13 subjects with amnesic mild cognitive impairment (aMCI), 11 subjects with early Alzheimer's disease (AD), and 16 control subjects. All participants underwent an examination of their intelligence, memory, and executive function and were subjected to DTI. Both aMCI and early AD subjects showed executive function impairment with differential performance in frontal‐related behaviors. Both aMCI and early AD subjects showed increased mean diffusivity in the genu of the corpus callosum and left frontal periventricular white matter (PVWM), whereas subjects with early AD showed an additional decrease in the fractional anisotropy of bilateral frontal PVWM and in the genu of the corpus callosum. The frontal PVWM was associated with performance on the Verbal Fluency Test, the Wisconsin Card Sorting Test (WCST), and Part B of the Trail Making Test. The parietal PVWM was associated with perseverative errors on the WCST and Part A of the Trail Making Test. In summary, executive function was impaired in subjects with aMCI and early AD and was associated with frontal and parietal PVWM changes. These changes may be due to early AD degeneration of the lateral cholinergic projections or to early change of the superior longitudinal fasciculus. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.     

In vivo parahippocampal white matter pathology as a biomarker of disease progression to Alzheimer's disease

Noninvasive diagnostic tests for Alzheimer's disease (AD) are limited. Postmortem diagnosis is based on density and distribution of neurofibrillary tangles (NFTs) and amyloid‐rich neuritic plaques. In preclinical stages of AD, the cells of origin for the perforant pathway within the entorhinal cortex are among the first to display NFTs, indicating its compromise in early stages of AD. We used diffusion tensor imaging (DTI) to assess the integrity of the parahippocampal white matter in mild cognitive impairment (MCI) and AD, as a first step in developing a noninvasive tool for early diagnosis. Subjects with AD (N = 9), MCI (N = 8), or no cognitive impairment (NCI; N = 20) underwent DTI‐MRI. Fractional anisotropy (FA) and mean (MD) and radial (RD) diffusivity measured from the parahippocampal white matter in AD and NCI subjects differed greatly. Discriminant analysis in the MCI cases assigned statistical membership of 38% of MCI subjects to the AD group. Preliminary data 1 year later showed that all MCI cases assigned to the AD group either met the diagnostic criteria for probable AD or showed significant cognitive decline. Voxelwise analysis in the parahippocampal white matter revealed a progressive change in the DTI patterns in MCI and AD subjects: whereas converted MCI cases showed structural changes restricted to the anterior portions of this region, in AD the pathology was generalized along the entire anterior–posterior axis. The use of DTI for in vivo assessment of the parahippocampal white matter may be useful for identifying individuals with MCI at highest risk for conversion to AD and for assessing disease progression. J. Comp. Neurol. 521:4300–4317, 2013. © 2013 Wiley Periodicals, Inc.     

Multiple diffusion indices reveals white matter degeneration in Alzheimer's disease and mild cognitive impairment: a tract-based spatial statistics study

Alzheimer's disease (AD) is a progressive neurodegenerative disease involving the decline of memory and other cognitive functions. Mild cognitive impairment (MCI) represents a transition phase between normal aging and early AD. The degeneration patterns of the white matter across the brain in AD and MCI remain largely unclear. Here we used diffusion tensor imaging and tract-based spatial statistics (TBSS) to investigate white matter changes in multiple diffusion indices (e.g., fractional anisotropy, axial, radial and mean diffusivities) in both AD and MCI patients. Compared with the normal controls, the AD patients had reduced fractional anisotropy and increased axial, radial and mean diffusivities in widespread white matter structures, including the corpus callosum and the white matter of lateral temporal cortex, the posterior cingulate cortex/precuneus and the fronto-parietal regions. Similar white matter regions with reduced anisotropy were also found in MCI patients but with a much less extent than in AD. Between the AD and MCI groups, there were significant differences in the axial and mean diffusivities of the white matter tracts adjacent to the posterior cingulate cortex/precuneus without anisotropy changes. Taken together, our findings based upon multiple diffusion indices (FA, axial, radial and mean diffusivities) suggest distinct degeneration behaviors of the white matter in AD and MCI.     

Cortical and subcortical white matter abnormalities in adults with remitted first‐episode mania revealed by Tract‐Based Spatial Statistics

Chan W‐Y, Yang G‐L, Chia M‐Y, Woon P‐S, Lee J, Keefe R, Sitoh Y‐Y, Nowinski WL, Sim K. Cortical and subcortical white matter abnormalities in adults with remitted first‐episode mania revealed by Tract‐Based Spatial Statistics.
Bipolar Disord 2010: 12: 383–389. © 2010 The Authors. Journal compilation © 2010 John Wiley & Sons A/S. Objectives: Abnormalities of brain white matter have been noted in structural magnetic resonance imaging and diffusion tensor imaging (DTI) studies of bipolar disorder, but there are fewer investigations specifically examining white matter integrity early in the course of illness. In this study, we employed DTI to elucidate white matter changes in adult patients with remitted first‐episode mania and hypothesized that first‐episode mania was associated with decreased fractional anisotropy in cortical (frontal) and subcortical (thalamus, striatum) white matter as well as white matter tracts (cingulum, corpus callosum). Methods: Diffusion tensor images were acquired from 16 patients with remitted first‐episode mania and 16 healthy controls matched for age, gender, handedness, and years of education. Fractional anisotropy and radial and axial diffusivities were analyzed using Tract‐Based Spatial Statistics. Results: Patients had lower fractional anisotropy and higher radial diffusivity in the left anterior frontal white matter, right posterior thalamic radiation, left cingulum, and bilateral sagittal striatum. In addition, increased radial diffusivity was found in the left corpus callosum. Conclusion: Our findings highlighted that white matter abnormalities were present by the time of remission of first‐episode mania. The widespread occurrence of these white matter abnormalities both in first‐episode mania and chronic bipolar disorder suggested that disruption of white matter cortical‐subcortical networks as well as projection, associative, and commissural tracts is a hallmark of the illness.     

抑郁症患者脑白质变化初步研究

目的：利用能够提示脑白质纤维完整性的磁共振弥散张量成像（DTI）探讨首发和复发重性抑郁症患者脑白质纤维的变化及其差异。方法：20例重性抑郁症患者（首发9例，复发11例）和20名正常对照者均经常规磁共振成像（MRI）平扫，未发现异常者继续进行DTI和结构MRI（3D）扫描，基于像素的全脑分析技术对DTI数据进行分析。结果：与对照组相比较，抑郁症组白质纤维结构在双侧额中回、右顶下小叶及双侧脑岛等区域白质的各向异性值（FA）显著降低（各脑区P均〈0.001，cluster〉30像素）;与首发抑郁症患者相比较，复发抑郁症患者右侧额上回、右顶叶、中央前回、中央后回及右顶下小叶等区域FA值降低更为显著（各脑区P均〈0.001，cluster〉10像素）。结论：重性抑郁症患者存在脑白质异常，抑郁反复发作会导致脑白质损害进一步加重。     

Peripheral oxidative stress biomarkers in mild cognitive impairment and Alzheimer's disease

Oxidative stress has been associated with normal aging and Alzheimer's disease (AD). However, little is known about oxidative stress in mild cognitive impairment (MCI) patients who present a high risk for developing AD. The aim of this study was to investigate plasma production of the lipid peroxidation marker, malonaldehyde (MDA) and to determine, in erythrocytes, the enzymatic antioxidant activity of catalase, glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione S-transferase (GST) in 33 individuals with MCI, 29 with mild probable AD and 26 healthy aged subjects. GR/GPx activity ratio was calculated to better assess antioxidant defenses. The relationship between oxidative stress and cognitive performance was also evaluated by the Mini Mental State Examination (MMSE). AD patients showed higher MDA levels than both MCI and healthy elderly subjects. MCI subjects also exhibited higher MDA levels compared to controls. Catalase and GPx activity were similar in MCI and healthy individuals but higher in AD. GR activity was lower in MCI and AD patients than in healthy aged subjects. Additionally, GR/GPx ratio was higher in healthy aged subjects, intermediate in MCI and lower in AD patients. No differences in GST activity were detected among the groups. MMSE was negatively associated with MDA levels (r = -0.31, p = 0.028) and positively correlated with GR/GPx ratio in AD patients (r = 0.68, p < 0.001). MDA levels were also negatively correlated to GR/GPx ratio (r = -0.31, p = 0.029) in the AD group. These results suggest that high lipid peroxidation and decreased antioxidant defenses may be present early in cognitive disorders.