Longitudinal brain metabolic changes from amnestic mild cognitive impairment to Alzheimer's disease.

International audienceA sensitive marker for monitoring progression of early Alzheimer's disease would help to develop and test new therapeutic strategies. The present study is aimed at investigating brain metabolism changes over time, as a potential monitoring marker, in patients with amnestic mild cognitive impairment, according to their clinical outcome (converters or non-converters), and in relation to their cognitive decline. Seventeen amnestic mild cognitive impairment patients underwent magnetic resonance imaging and 18FDG-positron emission tomography scans both at inclusion and 18 months later. Baseline and follow-up positron emission tomography data were corrected for partial volume effects and spatially normalized using magnetic resonance imaging data, scaled to the vermis and compared using SPM2. 'PET-PAC' maps reflecting metabolic per cent annual changes were created for correlation analyses with cognitive decline. In the whole sample, the greatest metabolic decrease concerned the posterior cingulate-precuneus area. Converters had significantly greater metabolic decrease than non-converters in two ventro-medial prefrontal areas, the subgenual (BA25) and anterior cingulate (BA24/32). PET-PAC in BA25 and BA24/32 combined allowed complete between-group discrimination. BA25 PET-PAC significantly correlated with both cognitive decline and PET-PAC in the hippocampal region and temporal pole, while BA24/32 PET-PAC correlated with posterior cingulate PET-PAC. Finally, the metabolic change in BA8/9/10 was inversely related to that in BA25 and showed relative increase with cognitive decline, suggesting that compensatory processes may occur in this dorso-medial prefrontal region. The observed ventro-medial prefrontal disruption is likely to reflect disconnection from the hippocampus, both indirectly through the cingulum bundle and posterior cingulate cortex for BA24/32, and directly through the uncinate fasciculus for BA25. Altogether, our findings emphasize the potential of 18FDG-positron emission tomography for monitoring early Alzheimer's disease progression

Asymmetrical hippocampal connectivity in mesial temporal lobe epilepsy: evidence from resting state fMRI

<p>Abstract</p> <p>Background</p> <p>Mesial temporal lobe epilepsy (MTLE), the most common type of focal epilepsy in adults, is often caused by hippocampal sclerosis (HS). Patients with HS usually present memory dysfunction, which is material-specific according to the hemisphere involved and has been correlated to the degree of HS as measured by postoperative histopathology as well as by the degree of hippocampal atrophy on magnetic resonance imaging (MRI). Verbal memory is mostly affected by left-sided HS, whereas visuo-spatial memory is more affected by right HS. Some of these impairments may be related to abnormalities of the network in which individual hippocampus takes part. Functional connectivity can play an important role to understand how the hippocampi interact with other brain areas. It can be estimated via functional Magnetic Resonance Imaging (fMRI) resting state experiments by evaluating patterns of functional networks. In this study, we investigated the functional connectivity patterns of 9 control subjects, 9 patients with right MTLE and 9 patients with left MTLE.</p> <p>Results</p> <p>We detected differences in functional connectivity within and between hippocampi in patients with unilateral MTLE associated with ipsilateral HS by resting state fMRI. Functional connectivity resulted to be more impaired ipsilateral to the seizure focus in both patient groups when compared to control subjects. This effect was even more pronounced for the left MTLE group.</p> <p>Conclusions</p> <p>The findings presented here suggest that left HS causes more reduction of functional connectivity than right HS in subjects with left hemisphere dominance for language.</p

Simultaneous PET-MRI Studies of the Concordance of Atrophy and Hypometabolism in Syndromic Variants of Alzheimer's Disease and Frontotemporal Dementia: An Extended Case Series

Background: Simultaneous PET-MRI is used to compare patterns of cerebral hypometabolism and atrophy in six different dementia syndromes. Objectives: The primary objective was to conduct an initial exploratory study regarding the concordance of atrophy and hypometabolism in syndromic variants of Alzheimer’s disease (AD) and frontotemporal dementia (FTD). The secondary objective was to determine the effect of image analysis methods on determination of atrophy and hypometabolism. Method: PET and MRI data were acquired simultaneously on 24 subjects with six variants of AD and FTD (n = 4 per group). Atrophy was rated visually and also quantified with measures of cortical thickness. Hypometabolism was rated visually and also quantified using atlas- and SPM-based approaches. Concordance was measured using weighted Cohen’s kappa. Results: Atrophy-hypometabolism concordance differed markedly between patient groups; kappa scores ranged from 0.13 (nonfluent/agrammatic variant of primary progressive aphasia, nfvPPA) to 0.49 (posterior cortical variant of AD, PCA). Heterogeneity was also observed within groups; the confidence intervals of kappa scores ranging from 0–0.25 for PCA to 0.29–0.61 for nfvPPA. More widespread MRI and PET changes were identified using quantitative methods than on visual rating. Conclusion: The marked differences in concordance identified in this initial study may reflect differences in the molecular pathologies underlying AD and FTD syndromic variants but also operational differences in the methods used to diagnose these syndromes. The superior ability of quantitative methodologies to detect changes on PET and MRI, if confirmed on larger cohorts, may favor their usage over qualitative visual inspection in future clinical diagnostic practic

Association of Obstructive Sleep Apnea with Episodic Memory and Cerebral Microvascular Pathology: A Preliminary Study

Objectives: To evaluate the impact of obstructive sleep apnea (OSA) on neurocognitive function and brain morphology in older adults with depression and cognitive impairment. Methods: We prospectively screened OSA with the STOP-Bang questionnaire in the last 25 patients enrolled into the Donepezil Treatment of Cognitive Impairment and Depression (DOTCODE) trial. High and low probability of OSA were defined as a STOP-Bang score of ≥5 (h-OSA) and of <5 (l-OSA), respectively. Baseline magnetic resonance imaging (MRI) was used to evaluate brain morphology. The initial 16 weeks of antidepressant treatment were part of the DOTCODE trial. Results: After 16 weeks of antidepressant treatment, the h-OSA group performed significantly worse on the Selective Reminding Test delayed recall task than the l-OSA group, controlling for baseline performance (F = 19.1, df = 1,22, p < 0.001). In 19 of 25 participants who underwent brain MRI, the h-OSA group had significantly greater volumes of MRI hyperintensities in deep white matter, periventricular white matter, and subcortical gray matter compared with the l-OSA group. There was no significant association between OSA and hippocampal or entorhinal cortex volumes in our sample, even after controlling for intracranial volume. Conclusions: OSA is associated with impaired verbal episodic memory and microvascular damage in older adults with depression and cognitive impairment. One possibility is that by contributing to cerebral microvascular damage, OSA may exacerbate progressive memory decline

Systemic inflammation and Alzheimer's disease biomarkers

Orientador: Marcio Luiz Figueredo BalthazarDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências MédicasResumo: A demência na doença de Alzheimer (DA) é um grave problema de saúde pública que tende a se intensificar devido, sobretudo, ao envelhecimento da população. Quanto aos aspectos clínicos da doença, o primeiro sintoma geralmente observado é a dificuldade em armazenar informações novas, afetando principalmente a memória episódica, à medida que a doença progride, outras funções cognitivas também são afetadas. A fisiopatologia da DA é caracterizada por uma série de alterações neuropatológicas que incluem: placas senis que contêm em excesso depósitos extracelulares de peptídeo ß-amiloide (ßA) e emaranhados neurofibrilares intracelulares que contêm proteína Tau hiperfosforilada (p-Tau), levando a uma maciça perda sináptica, morte neuronal e alterações funcionais em redes neurais, como na Default Mode Network (DMN). A conectividade funcional (CF) da DMN é alterada na DA devido ao acumulo de ßA em suas regiões, contribuindo para severidade dos sintomas cognitivos e clínicos. Alterações estruturais como atrofia cerebral, principalmente atrofia do hipocampo, também são observadas na doença. Há crescente evidência de que a inflamação sistêmica, através de mediadores inflamatórios, como por exemplo, as citocinas, desempenha um papel importante na produção e regulação dessas proteínas (ßA e Tau) presentes no líquido cefalorraquidiano (LCR). Existem vias de comunicação entre o cérebro e o sistema imune periférico que podem estar alteradas desde da fase pré-demencial, favorecendo ou não a progressão da doença, decorrente disso a inflamação sistêmica também tem sido associada com a cognição e morfologia cerebral. Nosso objetivo principal foi verificar a hipótese se a inflamação sistêmica pode ser associada com os principais biomarcadores da DA (proteínas do LCR e neuroimagem). Para isso, adquirimos imagens de ressonância magnética em 3T de 25 controles saudáveis, 45 pacientes com Comprometimento Cognitivo Leve amnéstico (CCLa) e 28 pacientes com DA leve. Observamos que os pacientes com CCLa nos quais detectamos IL-12, TNF-'alfa' e IL-6 apresentaram aumento da CF das regiões da DMN; os pacientes do grupo DA nos quais detectamos IL-12, IL-6, IL-10 e TNF-'alfa' apresentaram maior volume do hipocampo, menos ßA1-42 e diminuição na CF da DMN. Nossos resultados podem indicar uma possível relação entre o perfil de inflamação sistêmica e os biomarcadores da DAAbstract: Dementia in Alzheimer's disease (AD) is a serious public health problem that tends to intensify, mainly due to the aging of the population. Regarding the clinical aspects of the disease, the first symptom usually observed is the difficulty in storing new information, affecting episodic memory, as the disease progresses, other cognitive functions are affected. The pathophysiology of AD is characterized by a series of neuropathological changes that include: senile plaques that contain excess extracellular deposits ß-amyloid peptide (Aß) and intracellular neurofibrillary tangles that contain hyperphosphorylated Tau protein (p-Tau), leading to a massive neuronal death, and functional abnormalities in neural network, such as in the Default Mode Network (DMN). The functional connectivity (FC) of DMN is altered in AD due to the accumulation of Aß in its regions, contributing to the severity of cognitive and clinical symptoms. Structural changes such as brain atrophy, especially hippocampal atrophy, are also seen in the disease. There is increasing evidence that systemic inflammation, through inflammatory mediators, such as cytokines, plays an important role in the production and regulation of these proteins (ßA and Tau) present in cerebrospinal fluid (CSF). There are pathways of communication between the brain and the peripheral immune system that may be altered from the pre-dementia phase, favoring or not the progression of the disease, as a result of which systemic inflammation has also been associated with cerebral cognition and morphology. Our main objective was to verify the hypothesis that sistemic inflammation may be associated with the main biomarkers of AD (CSF proteins and neuroimaging). For this, we acquired magnetic resonance imaging in 3T of 25 healthy controls, 45 amnestic Mild Cognitive Impairment (aMCI) and 28 patients with mild AD. We observed that patients with aMCI in whom we detected IL-12, TNF-'alpha' and IL-6 showed increased FC of the regions of the DMN; the patients in the mild AD group in which we detected IL-12, IL-6, IL-10 and TNF-'alpha' had higher hippocampal volume, less Aß1-42, and decreased FC in DMN. Our results may indicate a possible relationship between the systemic inflammation profile and the biomarkers of ADMestradoNeurologiaMestra em Ciências133343/2015-42011/17092-0CNPQFAPES

Cardiorespiratory fitness and virtual navigation in healthy older adults

One of the earliest symptoms of Alzheimer’s disease (AD) and age-related cognitive decline is topographical disorientation or impairment to spatial navigation. Furthermore, aging and AD are associated with cortical gray-matter thinning, particularly in the medial temporal and posterior cingulate regions, which have been associated with spatial navigation. Aerobic exercise has been well-established as a beneficial intervention to curtail the neurodegenerative effects of aging. This study aims to explore the relationship between cardiorespiratory fitness (CRF), and two markers of AD and cognitive aging, virtual navigation ability and cortical thickness of the entorhinal, parahippocampal and retrosplenial regions. Cross-sectional data utilized in this study was collected from 23 healthy older adults (60-80 years). Measures included in our analyses consisted of estimated VO2max, T1-weighted structural MR images, and behavioral performance on a virtual navigation task, measured as numbers of objects located during recall. Cortical thickness of the regions of interest (ROIs) was determined by processing T1-weighted MR images in FreeSurfer. We hypothesized that greater CRF would correlate with improved virtual navigation performance and greater cortical thickness of ROIs. Our analyses did not reveal statistically significant relationships between CRF and navigation performance or CRF and cortical thickness. However, Pearson’s correlations found right retrosplenial cortical (RSC) thickness and navigation performance to be significantly related. Multiple regression models of right RSC thickness and navigation performance were performed controlling for age, sex, education and task version. These analyses revealed that greater right RSC thickness predicted navigation performance. Additionally, this model showed that older age predicts decline in navigation performance. Our findings did not survive multiple comparisons correction; nonetheless, the results provide promising insight to the relationship between cortical thickness and navigation performance in healthy aging. Further cross-sectional and longitudinal investigations with a larger sample size are required to assess the impact of CRF and exercise on cortical thickness and navigation abilities in healthy aging. Understanding these relationships would contribute to the expansive body of literature that has linked CRF and exercise to neuroprotective mechanisms in the aging brain

Understanding the neural basis of episodic amnesia in logopenic progressive aphasia: A multimodal neuroimaging study.

Logopenic progressive aphasia (LPA) is a neurodegenerative disorder characterised by profound naming and sentence repetition disturbances, attributable to disproportionately left-sided temporo-parietal atrophy. Accumulating evidence suggests, in addition to language impairments, the presence of stark verbal and nonverbal episodic memory dysfunction in LPA. The neurocognitive bases of such impairments, however, remain to be clarified. Here, we characterised episodic memory disruption and its corresponding grey and white matter correlates in the LPA syndrome. Nineteen LPA patients were contrasted with 23 matched typical Alzheimer's disease (AD) patients and 31 healthy Controls on standardized verbal and nonverbal episodic delayed recall measures. Participants further underwent structural magnetic resonance and diffusion-weighted imaging. Significant verbal memory deficits were evident in both patient groups, with LPA patients performing at an intermediate level to AD and Controls. For nonverbal memory, however, LPA performance was indistinguishable from that of AD, with both groups displaying marked impairments relative to Controls. Whole-brain voxel-based morphometry analyses revealed significant left temporo-parietal and left hippocampal atrophy in the LPA group. Covariate analyses showed that verbal and nonverbal amnesia in LPA correlated with grey matter integrity of bilateral frontoparietal and left medial temporal lobe regions. Notably, the common regions underpinning verbal and nonverbal memory dysfunction in LPA were the left orbitofrontal cortex and bilateral angular gyri in the inferior parietal cortex. The bilateral angular gyri, along with prefrontal and hippocampal regions further emerged as disease-general correlates of verbal and nonverbal memory performance. Alterations in mean diffusivity in structural connections between the left angular gyrus and medial temporal lobes were further associated with verbal memory performance in all participants. Our findings reveal, for the first time, the presence of pervasive memory impairments in LPA mediated by degeneration of a distributed prefrontal-hippocampal-parietal network, and disrupted parieto-hippocampal structural connectivity

Sex-Differences in the Early Detection of Dementia Risk Using a Cognitive-motor Integration Task

Cognitive-motor integration (CMI) involves concurrent thought and action which requires the interaction of large brain networks. Our research objectives were to examine the effect that dementia risk has on the ability to integrate rules into action and to investigate sex-related differences in this rule-based motor performance. Given that early-stage dementia involves neural network dysfunction, problems with CMI may prove useful for early dementia detection. Males and females at high- and low-dementia risk were tested on increasingly spatially-dissociated visuomotor tasks. We observed significantly greater endpoint error scores and corrective path lengths in females compared to males in the most complex CMI condition. These data suggest that underlying brain networks controlling simultaneous thought and action differ between the sexes, and that dementia risk may affect female CMI performance to a greater extent. Thus, sex-related differences must be taken into account when assessing CMI performance as a means to examine dementia risk-related functional abilities