弥漫性轴索损伤后早期磁共振弥散张量成像与工作记忆障碍的相关性研究

目的探讨磁共振弥散张量成像(DTI)对弥漫性轴索损伤(DAI)导致工作记忆障碍早期诊断及预后评估的价值。方法分别对10例DAI患者(DAI组)和10例健康志愿者(正常对照组)行DTI检查,并对两组DTI图像的钩束、皮质脊髓束、胼胝体和扣带回感兴趣区的部分各向异性(FA)值进行比较分析。DAI后6个月对患者与健康志愿者行认知量表评估,并行对比分析;另外将DAI组FA值与其认知量表评分行直线相关分析。结果与对照组相比,DAI患者4个感兴趣区的FA值显著降低(P<0.05),恢复期总体认知能力略降低,但无统计学意义(P>0.05),而工作记忆功能却显著降低(P<0.05)。DAI患者中的钩束和皮质脊髓束的FA值与工作记忆功能呈正相关(r分别为0.898和0.797,P<0.05);胼胝体和扣带回FA值与工作记忆功能无明显相关性(r分别为0.432和0.387,P>0.05)。结论 DTI技术可为DAI导致的工作记忆障碍早期诊断和预后评估提供依据。     

皮质下缺血性血管性痴呆患者大脑联络纤维弥散张量成像研究

目的应用磁共振弥散张量成像(DTI)技术,研究皮质下缺血性血管性痴呆(SIVD)患者脑白质联络纤维变化的特点,以探讨弥散张量成像在诊断SIVD患者中的诊断价值。方法对60例SIVD患者和45例年龄匹配的非痴呆对照者,应用简易智能状态检查量表(MMSE)、蒙特利尔认知测评量表(Mo CA)及临床痴呆量表(CDR)进行认知功能评估;用全脑磁共振DTI技术,测量上纵束、下额枕束(额部、额颞部和颞部)、胼胝体膝部和压部和扣带束多个感兴趣区的各向异性分数(FA)值和表观弥散系数(ADC)值。结果与对照组比较,SIVD组双侧下额枕束、双侧扣带束、左侧上额枕束和胼胝体膝部FA值明显下降,ADC值明显升高,差异有统计学意义(均P<0.05),右侧上额枕束和胼胝体压部的FA值和ADC值差异无统计学意义(P>0.05)。结论 SIVD患者多个感兴趣区的DTI改变证明联络纤维损伤明显;全脑DTI研究是SIVD患者敏感可靠的技术方法,有助于理解SIVD患者的认知功能与联络纤维损害的关系。     

皮质下缺血性血管性痴呆患者脑白质损害的磁共振弥散张量成像研究

目的:应用磁共振弥散张量成像技术(DTI)观察皮质下缺血性血管性痴呆(SIVD)患者脑白质损害程度,探讨DTI对SIVD白质损害的评估及与阿尔茨海默病(AD)鉴别诊断价值。方法:研究对象分为3组,分别是健康老年人(NC)、皮质下缺血性血管性痴呆(SIVD)患者、AD患者,每组各20例。行常规MR I和DTI扫描后,测定相同感兴趣区(RO I)的各向异性分数(FA)值和表观扩散系数(ADC)值进行比较。结果:SIVD组下额枕束、胼胝体膝部、胼胝体压部、上纵束等部位FA值下降,ADC值升高,与NC、AD组比较差异有统计学意义(P<0.05)。与NC组比较,AD组前额叶、颞叶、海马、下额枕束、胼胝体膝部和扣带束等部位FA值降低,颞叶、海马等部位ADC值升高,两组差异具有显著性(P<0.05);结论:DTI可以用来评估痴呆患者白质损害的程度,SIVD患者以下额枕束、胼胝体膝部、胼胝体压部、上纵束等部位受累为主,可作为与AD鉴别的客观指标。     

磁共振弥散张量成像对预测皮质下缺血性血管性痴呆患者认知功能障碍的价值

目的应用磁共振弥散张量成像(DTI)技术,探讨皮质下缺血性血管性痴呆(SIVD)患者不同联络纤维感兴趣区弥散张量参数改变与认知功能的关系。方法对60例SIVD患者和40例年龄匹配的非痴呆对照者,采用测定感兴趣区弥散张量参数的方法,比较其纤维束完整性差异及与神经心理学量表的关系。结果 (1)与对照组比较,SIVD组双侧下额枕束、双侧扣带束、左侧上纵束和胼胝体膝部的FA值显著下降及ADC值显著升高;(2)双侧额叶前部皮质下白质FA值与MMSE及Mo CA评分呈明显正相关;(3)双侧海马区、双侧扣带束的FA值与MMSE评分呈明显正相关。结论不同脑区的弥散张量参数变化特点有助于SIVD患者认知功能障碍的早期预测。     

胼胝体和扣带回弥散张量成像改变对皮质下缺血性血管性痴呆患者认知功能障碍的影响

目的应用磁共振弥散张量成像(DTI)技术,探讨皮质下缺血性血管性痴呆(SIVD)患者胼胝体和扣带回弥散张量参数改变与认知功能的关系。方法对60例SIVD患者和40例年龄匹配的非痴呆对照者,采用测定感兴趣区弥散张量参数的方法,比较其纤维束完整性差异及与MMSE的关系。结果 (1)与对照组比较,SIVD组胼胝体膝部、双侧扣带回的FA值显著下降及ADC值显著升高,而胼胝体压部的FA值和ADC值无显著性差异。(2)胼胝体膝部、双侧扣带回的FA值与MMSE评分呈明显正相关。结论胼胝体和扣带回弥散张量改变有助于SIVD患者认知功能障碍的早期预测。     

精神分裂症首次发病患者的脑扩散张量成像研究

目的 利用磁共振扩散张量成像(DTI)技术研究未经药物治疗的精神分裂症首次发病(以下简称首发)患者主要脑区白质纤维束的异常.方法 选取26例首发精神分裂症患者(患者组)和20名健康志愿者(对照组)行脑DTI扫描(两组均为右利手),测量胼胝体膝部、压部、双侧额叶白质、扣带束前部及海马头的部分各向异性(FA)值.结果 (1)对照组左侧扣带束FA值(0.428±0.067)大于右侧(0.375±0.079;P＜0.05).(2)患者组两侧相对应感兴趣区FA值差异均无统计学意义(P＞0.05).(3)患者组左右侧胼胝体压部FA值(均为0.734±0.085)、左右侧扣带束前部FA值(0.300±0.068和0.306 4±0.062)均低于对照组(0.785±0.045,0.428±0.067,0.375±0.079;均P＜0.05).结论 首发精神分裂症患者存在双侧扣带束、胼胝体压部白质纤维束的受损,支持脑内连接异常假说.     

弥散张量纤维束成像对多发性硬化看似正常脑白质损伤定量分析

目的分析复发缓解型多发性硬化(MS)患者看似正常白质(NAWM)纤维束微结构变化。方法 17例MS患者与年龄、性别匹配健康志愿者参与研究。使用TrackVIS软件持续纤维跟踪成像方法重建白质纤维束,记录白质纤维束的部分各向异性(FA)、表观弥散系数(ADC)和纤维束容积值,进行数据分析。结果 MS及健康对照组各男8例,女9例。与健康对照组相比,MS患者通过胼胝体压部和整个胼胝体神经纤维束的容积下降,两者相比差异有统计学意义(P0.05)。MS患者通过胼胝体膝部、压部及整个胼胝体纤维束的FA值下降(P0.05)。与病灶对侧NAWM相比,通过MS患者病灶的纤维束容积更小,FA值降低,ADC值升高(P0.05)。较之健康对照组,通过患者病灶对侧NAWM的纤维束FA值降低(P0.05)。结论弥散张量纤维成像技术可用于早期NAWM微小损伤的评估,FA值可作为NAWM纤维束损伤的敏感指标。     

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。     

帕金森病合并认知功能障碍与脑白质纤维束改变的关系

目的探讨帕金森病(PD)合并认知功能障碍与认知相关脑白质纤维束改变的关系。方法纳入PD患者35例,根据蒙特利尔认知评估量表(MoCA)评分将PD患者分为PD认知功能正常组(PD-nCI,n=14)和PD认知功能障碍组(PD-CI,n=21);另选择同期行查体的健康志愿者20名作为对照组。所有受试者行弥散张量成像(DTI)检查,通过基于纤维束的空间统计分析(tract-based spatial statistics,TBSS)方法选出与认知相关的脑白质纤维束,并测量各纤维束部分各向异性(fractional anisotropy,FA)值。比较各组不同纤维束FA值差异,采用Pearson相关分析法分析PD-CI组差异有统计学意义的纤维束FA值与MoCA评分的相关性。结果(1)3组间胼胝体膝部、胼胝体体部、胼胝体压部、右扣带回(海马)、左扣带回(海马)、右穹窿/终纹、左穹窿/终纹、右上额枕束、左上额枕束FA值比较存在统计学差异(均P0.05),PD-nCI组和PD-CI组间胼胝体膝部、胼胝体体部、胼胝体压部、右扣带回(海马)、左扣带回(海马)、左穹窿/终纹、右上额枕束、左上额枕束FA值比较存在统计学差异(均P0.05);(2)PD-CI组胼胝体压部、右扣带回(海马)、右上额枕束、左上额枕束FA值与MoCA评分呈正相关(均P0.05)。结论 PD患者认知功能损害程度与胼胝体压部、右扣带回(海马)、右上额枕束和左上额枕束等纤维束病变严重程度呈正相关。     

轻微型肝性脑病磁共振扩散加权成像和扩散张量成像的定量研究

目的通过磁共振扩散加权成像(DWI)和扩散张量成像(DTI)定量分析轻微型肝性脑病(MHE)患者脑功能的异常改变,探讨DWI和DTI在MHE中的应用价值。方法30例肝硬化患者经神经心理测试评分量表测试后,分为MHE组16例和无MHE单纯肝硬化组14例,同时选取15例健康志愿者为正常对照组。所有受试者均行DWI与DTI扫描,选取脑内8个部位为感兴趣区,计算各部位的表观扩散系数(ADC)值和各向异性分数(FA)值。结果18例肝硬化患者于T1WI图像上可见到双侧内囊、苍白球对称性高信号。额叶、枕叶白质、胼胝体膝部、胼胝体压部、内囊前肢、内囊后肢、尾状核头部由正常组、单纯肝硬化组至MHE组ADC值逐渐增加,且MHE组的ADC值较肝硬化组和正常组增加,差异有统计学意义(P<0.05);胼胝体膝部和压部的FA值由正常组、单纯肝硬化组至MHE组逐渐降低,差异有统计学意义(P<0.05)。结论DWI与DTI联合应用能够预测肝硬化患者MHE的进展程度,具有潜在的临床价值。     

Reduced white matter fractional anisotropy and clinical symptoms in schizophrenia: a voxel-based diffusion tensor imaging study

Although not consistently replicated, diffusion tensor imaging (DTI) studies in schizophrenia have revealed lower fractional anisotropy (FA) in various white matter regions, a finding consistent with the disruption of white matter integrity. In this study, we used voxel-based DTI to investigate possible whole-brain differences in the white matter FA values between 58 schizophrenia patients and 58 healthy controls. We also explored the association between FA values and clinical symptoms in schizophrenia. Compared with the controls, the schizophrenia patients showed significant FA reductions in bilateral superior longitudinal fasciculus, bilateral inferior fronto-occipital fasciculus, and genu of right internal capsule. Furthermore, in the patient group, the FA value of the anterior part of the corpus callosum was negatively correlated with the avolition score on the Scale for the Assessment of Negative Symptoms. These findings suggest widespread disruption of white matter integrity in schizophrenia, which could partly explain the severity of negative symptomatology.     

White matter abnormalities and their impact on attentional performance in adult attention-deficit/hyperactivity disorder

Inattention is the most important behavioral feature of adult patients with attention-deficit/hyperactivity disorder (ADHD). Neuroimaging studies in ADHD have demonstrated abnormalities primarily in the frontostriatal circuitry and were mostly conducted in children. We investigated white matter (WM) integrity in adult ADHD patients and the correlation of WM microstructure and neuropsychological parameters in 37 (21 men) never-medicated adult ADHD patients and 34 age- and gender-matched healthy controls. All subjects underwent clinical interviews, rating scales, and neuropsychological tests of attentional performance. Diffusion tensor imaging (DTI) was acquired, and 12 WM regions-of-interest (ROIs) within the attentional network were chosen. Group differences of mean fractional anisotropy (FA) and mean diffusivity (MD) values were calculated for each ROI, and patients' DTI measures were then correlated with measures of attentional performance. FA values in ADHD patients were significantly reduced in the left inferior longitudinal fasciculus (ILF), while MD values were significantly increased in ADHD patients in the frontal portion of the left frontooccipital fasciculus (IFO). In ADHD patients, MD values were negatively correlated with attentional performance in the left ILF. Our findings provide further support for disturbed frontostriatal structural connectivity and also point to an involvement of the left temporal white matter with an impact on attentional performance.     

Abnormal white matter integrity in young children with autism

This study investigated white matter integrity in young children with autism using diffusion tensor imaging (DTI). Twenty-two children with autism, mean age 3:2 years, and 32 controls, mean age 3:4 years, participated in the study. Tract-based spatial statistics (TBSS) revealed white matter abnormalities in several distinct clusters within the genu and body of the corpus callosum (CC), left superior longitudinal fasciculus (SLF) and right and left cingulum (Cg). TBSS-VOIs analysis was performed in the clusters where differences in fractional anisotropy (FA) were detected to investigate the relationship between changes in FA and diffusivity indices. In all VOIs, increase in FA was caused by a decrease in radial diffusivity (Dr), while no changes in axial diffusivity (Da) or mean diffusivity (MD) were observed. Tractography analysis was applied to further study the CC, SLF, and Cg. Witelson parcellation scheme was used for the CC. Significant increase in FA was seen in children with autism in the mid-body of the CC as well as in the left Cg. It is suggested that such abnormal white matter integrity in young children with autism may adversely affect connectivity between different brain regions and may be linked to some of the behavioral impairments apparent in autism.     

Diffusion tensor imaging and white matter lesions at the subacute stage in mild traumatic brain injury with persistent neurobehavioral impairment

Mild traumatic brain injury (mTBI) can induce long‐term behavioral and cognitive disorders. Although the exact origin of these mTBI‐related disorders is not known, they may be the consequence of diffuse axonal injury (DAI). Here, we investigated whether MRI at the subacute stage can detect lesions that are associated with poor functional outcome in mTBI by using anatomical images (T₁) and diffusion tensor imaging (DTI). Twenty‐three patients with mTBI were investigated and compared with 23 healthy volunteers. All patients underwent an MRI investigation and clinical tests between 7 and 28 days (D15) and between 3 and 4 months (M3) after injury. Patients were divided in two groups of poor outcome (PO) and good outcome (GO), based on their complaints at M3. Groupwise differences in gray matter partial volume between PO patients, GO patients and controls were analyzed using Voxel‐Based Morphometry (VBM) from T₁ data at D15. Differences in microstructural architecture were investigated using Tract‐Based Spatial Statistics (TBSS) and the diffusion images obtained from DTI data at D15. Permutation‐based non‐parametric testing was used to assess cluster significance at p < 0.05, corrected for multiple comparisons. Twelve GO patients and 11 PO patients were identified on the basis of their complaints. In PO patients, gray matter partial volume was significantly lower in several cortical and subcortical regions compared with controls, but did not differ from that of GO patients. No difference in diffusion variables was found between GO and controls. PO patients showed significantly higher mean diffusivity values than both controls and GO patients in the corpus callosum, the right anterior thalamic radiations and the superior longitudinal fasciculus, the inferior longitudinal fasciculus and the fronto‐occipital fasciculus bilaterally. In conclusion, PO patients differed from GO patients by the presence of diffusion changes in long association white matter fiber tracts but not by gray matter partial volume. These results suggest that DTI at the subacute stage may be a predictive marker of poor outcome in mTBI. Hum Brain Mapp, 2011. © 2010 Wiley‐Liss, Inc.     

Diffusion tensor imaging (DTI) in the detection of white matter lesions in patients with mild cognitive impairment (MCI)

Mild cognitive impairment (MCI) is recognized as a precursor to dementia. The amnestic MCI progresses usually to Alzheimer disease. Amnestic MCI multiple domain (md-MCI) seems to progress more rapidly than amnestic MCI single domain (a-MCI). In an attempt to identify patients at risk, we examined white matter changes in MCI subtypes using diffusion tensor imaging (DTI). We also tried to correlate DTI findings to neuropsychological tests. Forty-four amnestic single domain (a-MCI) patients, 19 amnestic multi domain (md-MCI), and 25 cognitively normal (NC) controls were included in the present study. All participants were assessed clinically using a battery of cognitive tests. DTI was performed to measure fractional anisotropy (FA) and apparent diffusion coefficient (ADC). Areas studied were corpus callosum, posterior cingulum (PC), anterior cingulum (AC), and superior longitudinal fasciculus (SLF). ADC and FA of the above areas were related to the scores of certain neuropsychological tests that evaluate visual and verbal memory. No difference in DTI measurements was found between the two MCI subtypes. ADC in MCI cases was increased in comparison with NC in the genu, PC, right SLF, and left AC. FA was spared. Verbal memory was related to ADC of the genu, PC, right AC and right SLF, and to FA of the left SLF. Visual memory was related to ADC of the genu, PC, right AC, and SLF. The strongest correlation found was between the visual memory and the ADC of the right PC (Spearman ρ = 0.45, p < 0.001). DTI revealed that ADC was increased in certain brain areas in MCI patients. No difference in DTI measurements was found between the two MCI subtypes. DTI indices correlate with cognitive performance.     

Structural connectivity of the frontal lobe in children with drug-resistant partial epilepsy

The superior longitudinal fasciculus (SLF) II and cingulum are two white matter tracts important for attention and other frontal lobe functions. These functions are often disturbed in children with drug-resistant (DR) partial epilepsy, even when no abnormalities are seen on conventional MRI. We set out to determine whether abnormalities in these structures might be depicted on diffusion tensor imaging (DTI) studies in the absence of abnormalities on conventional MRI. We compared the DTI findings of 12 children with DR partial epilepsy with those of 12 age- and gender-matched controls. We found that the SLF II fractional anisotropy (FA) values of the patients were significantly lower than those of the controls (means: 0.398±0.057 and 0.443±0.059, respectively, P=0.002). Similarly, apparent diffusion coefficient (ADC) and parallel diffusivity values for SLF II were also significantly lower in the patients. There were no differences in the FA and ADC values of the cingulum. Our findings are consistent with abnormal structural connectivity of the frontal lobe in children with DR partial epilepsy and provide a possible explanation for the previously reported functional abnormalities related to the SLF II in these patients.     

The temporal stem in traumatic brain injury: preliminary findings

The temporal stem (TS) of the temporal lobe is a major white matter (WM) region containing several major pathways that connect the temporal lobe with the rest of the brain. Because of its location, it may be particularly vulnerable to shear-strain effects resulting from traumatic brain injury (TBI). A case vignette is presented in a patient with severe brain injury and focal TS pathology. Also, 12 severe TBI subjects unselected for TS pathology were compared to demographically matched, neurologically-intact controls using diffusion tensor imaging (DTI) to examine white matter tracts associated with the TS, including the inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF), arcuate fasciculus (AF), cingulum bundle (CB) and the uncinate fasciculus (UF). For each tract, fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were computed and compared between the two groups and also examined in relationship to memory performance in the TBI subjects. Significant FA and ADC differences were observed in all tracts in the TBI patients compared to controls, with several relationships with memory outcome noted in the IFOF, ILF and AF. Based on these preliminary findings, the potential role of TBI-induced WM disconnection involving the TS is discussed as well as the relationship of TS damage to neurobehavioral outcome. The need for future studies specifically examining the role of TS injury in TBI is emphasized.     

Structural connectivity associated with familial risk for mental illness: A meta‐analysis of diffusion tensor imaging studies in relatives of patients with severe mental disorders

Schizophrenia (SCZ), bipolar disorder (BD), and major depressive disorder (MDD) are heritable conditions with overlapping genetic liability. Transdiagnostic and disorder‐specific brain changes associated with familial risk for developing these disorders remain poorly understood. We carried out a meta‐analysis of diffusion tensor imaging (DTI) studies to investigate white matter microstructure abnormalities in relatives that might correspond to shared and discrete biomarkers of familial risk for psychotic or mood disorders. A systematic search of PubMed and Embase was performed to identify DTI studies in relatives of SCZ, BD, and MDD patients. Seed‐based d Mapping software was used to investigate global differences in fractional anisotropy (FA) between overall and disorder‐specific relatives and healthy controls (HC). Our search identified 25 studies that met full inclusion criteria. A total of 1,144 relatives and 1,238 HC were included in the meta‐analysis. The overall relatives exhibited decreased FA in the genu and splenium of corpus callosum (CC) compared with HC. This finding was found highly replicable in jack‐knife analysis and subgroup analyses. In disorder‐specific analysis, compared to HC, relatives of SCZ patients exhibited the same changes while those of BD showed reduced FA in the left inferior longitudinal fasciculus (ILF). The present study showed decreased FA in the genu and splenium of CC in relatives of SCZ, BD, and MDD patients, which might represent a shared familial vulnerability marker of severe mental illness. The white matter abnormalities in the left ILF might represent a specific familial risk for bipolar disorder.     

White matter abnormalities observed in bipolar disorder: a diffusion tensor imaging study

OBJECTIVES: An increased incidence in white matter abnormalities is among the most frequently reported brain change in patients with bipolar disorder. The objective of the present study was to examine white matter tract integrity, using diffusion tensor imaging (DTI), in bipolar patients and healthy comparison subjects. METHODS: Eleven DSM-IV bipolar I patients and 10 healthy age- and sex-matched controls were studied. DTI data were acquired on a 1.5 Tesla scanner. Fractional anisotropy (FA) and diffusivity (trace) were determined from axial images using region of interest (ROI) analyses. The ROIs were manually placed in the midline and forward projecting arms of the genu (anterior) and the midline of the splenium (posterior) of the corpus callosum. RESULTS: Bipolar patients had significantly higher FA in the midline of the genu compared with healthy controls. Regional white matter differences were also observed, with significantly lower FA in the genu than forward projecting regions in both groups and lower FA in the genu than the splenium in controls. CONCLUSIONS: Diffusion tensor imaging revealed significant microstructural differences in the genu, as measured by elevated FA in bipolar patients compared with healthy controls. These preliminary findings further support the hypothesis that anomalous frontal brain mechanisms may be associated with bipolar disorder.