The results of this study indicate that the DMN abnormalities observed in patients with AD represent an accelerated aging pattern of connectivity compared with matched controls.

Objective: To use diffusion tensor imaging (DTI) to assess gray matter and white matter tract diffusion in behavioral variant frontotemporal dementia (bvFTD), semantic dementia (SMD), and progressive nonfluent aphasia (PNFA). Methods:This was a case-control study where 16 subjects with bvFTD, 7 with PNFA, and 4 with SMD were identified and matched by age and gender to 19 controls. All subjects had 3-T head MRI with a DTI sequence with diffusion encoding in 21 directions. Gray matter mean diffusivity (MD) was assessed using a region-of-interest (ROI) and voxel-level approach, and voxel-based morphometry was used to assess patterns of gray matter loss. White matter tract diffusivity (fractional anisotropy and radial diffusivity) was assessed by placing ROIs on tracts of interest. Results:In bvFTD, increased gray matter MD and gray matter loss were identified bilaterally throughout frontal and temporal lobes, with abnormal diffusivity observed in white matter tracts that connect to these regions. In SMD, gray matter loss and increased MD were identified predominantly in the left temporal lobe, with tract abnormalities observed in the inferior longitudinal fasciculus and uncinate fasciculus. In PNFA, gray matter loss and increased MD were observed in left inferior frontal lobe, insula, and supplemental motor area, with tract abnormalities observed in the superior longitudinal fasciculus. Conclusions:The diffusivity of gray matter is increased in regions that are atrophic in frontotemporal dementia, suggesting disruption of the cytoarchitecture of remaining tissue. Furthermore, damage was identified in white matter tracts that interconnect these regions, supporting the hypothesis that these diseases involve different and specific brain networks. Neurology ® 2010;74:1279 -1287 GLOSSARY AAL ϭ automated anatomic labeling; AC ϭ anterior cingulate; ADRC ϭ Alzheimer's Disease Research Center; ADPR ϭ Alzheimer's Disease Patient Registry; AOS ϭ apraxia of speech; bvFTD ϭ behavioral variant frontotemporal dementia; CV ϭ coefficient of variation; DA ϭ axial diffusivity; DR ϭ radial diffusivity; DTI ϭ diffusion tensor imaging; FA ϭ fractional anisotropy; FDR ϭ false discovery rate; FOV ϭ field of view; FTD ϭ frontotemporal dementia; FWHM ϭ full-width at half-maximum; GCC ϭ genu of the corpus callosum; HDW ϭ high-dimensional warping; ILF ϭ inferior longitudinal fasciculus; MD ϭ mean diffusivity; MPRAGE ϭ magnetization prepared rapid acquisition gradient echo; PC ϭ posterior cingulate; PNFA ϭ progressive nonfluent aphasia; PVC ϭ partial volume correction; ROI ϭ region of interest; SLF ϭ superior longitudinal fasciculus; SMD ϭ semantic dementia; UNC ϭ uncinate fasciculus.Diffusion tensor imaging (DTI) has recently emerged as a valuable technique for assessing structural changes in the brain.1-3 It can provide information on microstructural tissue integrity by measuring changes in water diffusion through tissue. This is particularly useful for assessing the integrity of white matter tracts because DTI can provide a measure ...

Objective: To identify the patterns of diffusivity changes in patients with dementia with Lewy bodies (DLB) and Alzheimer disease (AD) and to determine whether diffusion tensor MRI (DTI) is complementary to structural MRI in depicting the tissue abnormalities characteristic of DLB and AD. Methods:We studied clinically diagnosed age-, gender-, and education-matched subjects with DLB (n ϭ 30), subjects with AD (n ϭ 30), and cognitively normal (CN) subjects (n ϭ 60) in a case-control study. DTI was performed at 3T with a fluid-attenuated inversion recovery-based DTI sequence that enabled cortical diffusion measurements. Mean diffusivity (MD) and gray matter (GM) density were measured from segmented cortical regions. Tract-based diffusivity was measured using color-coded fractional anisotropy (FA) maps. Results:Patients with DLB were characterized by elevated MD in the amygdala and decreased FA in the inferior longitudinal fasciculus (ILF). ILF diffusivity was associated with the presence of visual hallucinations (p ϭ 0.007), and amygdala diffusivity was associated with Unified Parkinson's Disease Rating Scale (r ϭ 0.50; p ϭ 0.005) in DLB. In contrast, patients with AD were characterized by elevated MD in the medial temporal, temporal, and parietal lobe association cortices and decreased FA in the fornix, cingulum, and ILF. Amygdala diffusivity was complementary to GM density in discriminating DLB from CN; hippocampal and parahippocampal diffusivity was complementary to GM density in discriminating AD from CN. Conclusion:Increased amygdalar diffusivity in the absence of tissue loss in dementia with Lewy bodies (DLB) may be related to microvacuolation, a common pathology associated with Lewy body disease in the amygdala. Diffusivity measurements were complementary to structural MRI, demonstrating that measures of diffusivity on diffusion tensor MRI are valuable tools for characterizing the tissue abnormalities characteristic of Alzheimer disease and DLB. Neurology ® 2010;74:1814 -1821 GLOSSARY AD ϭ Alzheimer disease; CN ϭ cognitively normal; DLB ϭ dementia with Lewy bodies; DTI ϭ diffusion tensor MRI; FA ϭ fractional anisotropy; FDR ϭ false discovery rate; FLAIR ϭ fluid-attenuated inversion recovery; GM ϭ gray matter; ILF ϭ inferior longitudinal fasciculus; LB ϭ Lewy body; MD ϭ mean diffusivity; RBD ϭ REM sleep behavior disorder; ROI ϭ region of interest; SLF ϭ superior longitudinal fasciculus; TE ϭ echo time; TI ϭ inversion time; TR ϭ repetition time; UPDRS ϭ Unified Parkinson's Disease Rating Scale; WM ϭ white matter.Dementia with Lewy bodies (DLB) is the second most common cause of neurodegenerative dementia after Alzheimer disease (AD).1 Although patients with Lewy body (LB) pathology typically have some AD pathology, 2 noninvasive imaging markers that can distinguish the contribution of these different pathologies to the dementia syndrome may be useful for the differential diagnosis and may provide insight into the pathologic mechanisms underlying these disorders.Diffusion tensor MRI (DTI) provides infor...

ObjectiveTo examine default mode and salience network functional connectivity as a function of APOE ε4 status in a group of cognitively normal age-, sex-, and education-matched older adults.DesignCase-control study.SubjectsFifty-six cognitively normal APOE ε4 carriers and 56 age-, sex- and education-matched cognitively normal APOE ε4 noncarriers.Main Outcome MeasureAlterations in in-phase default mode and salience network connectivity in APOE ε4 carriers compared with APOE ε4 noncarriers ranging from 63 to 91 years of age.ResultsA posterior cingulate seed revealed decreased in-phase connectivity in regions of the posterior default mode network that included the left inferior parietal lobe, left middle temporal gyrus, and bilateral anterior temporal lobes in the ε4 carriers relative to APOE ε4 noncarriers. An anterior cingulate seed showed greater in-phase connectivity in the salience network including the cingulate gyrus, medial prefrontal cortex, bilateral insular cortex, striatum, and thalamus in APOE ε4 carriers vs noncarriers. There were no groupwise differences in brain anatomy.ConclusionsThe observation of functional alterations in default mode and salience network connectivity in the absence of structural changes between APOE ε4 carriers and noncarriers suggests that alterations in connectivity may have the potential to serve as an early biomarker.

Objective: To determine whether functional connectivity is altered in subjects with mutations in the microtubule associated protein tau (MAPT) gene who were asymptomatic but were destined to develop dementia, and to compare these findings to those in subjects with behavioral variant frontotemporal dementia (bvFTD). Methods:In this case-control study, we identified 8 asymptomatic subjects with mutations in MAPT and 8 controls who screened negative for mutations in MAPT. Twenty-one subjects with a clinical diagnosis of bvFTD were also identified and matched to 21 controls. All subjects had resting-state fMRI. In-phase functional connectivity was assessed between a precuneus seed in the default mode network (DMN) and a fronto-insular cortex seed in the salience network, and the rest of the brain. Atlas-based parcellation was used to assess functional connectivity and gray matter volume across specific regions of interest. Results:The asymptomatic MAPT subjects and subjects with bvFTD showed altered functional connectivity in the DMN, with reduced in-phase connectivity in lateral temporal lobes and medial prefrontal cortex, compared to controls. Increased in-phase connectivity was also observed in both groups in the medial parietal lobe. Only the bvFTD group showed altered functional connectivity in the salience network, with reduced connectivity in the fronto-insular cortex and anterior cingulate. Gray matter loss was observed across temporal, frontal, and parietal regions in bvFTD, but not in the asymptomatic MAPT subjects. Conclusions:Functional connectivity in the DMN is altered in MAPT subjects before the occurrence of both atrophy and clinical symptoms, suggesting that changes in functional connectivity are early features of the disease. Neurology ® 2011;77:866-874 GLOSSARY AD ϭ Alzheimer disease; BOLD ϭ blood oxygenation level-dependent; bvFTD ϭ behavioral variant frontotemporal dementia; DMN ϭ default mode network; FOV ϭ field of view; FTD ϭ frontotemporal dementia; FWE ϭ familywise error; ICA ϭ independent component analysis; MPRAGE ϭ magnetization-prepared rapid acquisition gradient echo; PPND ϭ pallido-ponto-nigral degeneration; ROI ϭ region of interest; TE ϭ echo time; TIV ϭ total intracranial volume; TR ϭ repetition time.Frontotemporal dementia (FTD) is a progressive neurodegenerative disorder characterized by behavioral and language deficits.1,2 A large proportion of subjects with FTD have an autosomal dominant pattern of inheritance, 3,4 with many showing mutations in the microtubule associated protein tau (MAPT) gene.5 Subjects with mutations in MAPT typically present with behavioral variant FTD (bvFTD), with poor semantic abilities, 6 -8 and show predominant temporal atrophy, with less severe involvement of frontal and parietal lobes.9,10 Families characterized by the presence of mutations in MAPT provide the ideal construct to identify preclinical disease changes. Case studies assessing imaging in asymptomatic MAPT carriers show