Global Hippocampal Atrophy Research Articles

Exploring graded profiles of hippocampal atrophy along the anterior-posterior axis in semantic dementia and Alzheimer’s disease

Mounting evidence indicates marked hippocampal degeneration in semantic dementia (SD) however, the spatial distribution of hippocampal atrophy profiles in this syndrome remains unclear. Using a recently developed parcellation approach, we extracted hippocampal volumes from four distinct subregions running from anterior to posterior along the longitudinal axis (anterior, intermediate rostral, intermediate caudal, and posterior). Volumetric differences in hippocampal subregions were compared between 21 SD, 24 matched Alzheimer’s disease (AD), and 27 healthy older Control participants. Despite comparable overall hippocampal volume loss, SD and AD groups diverged in terms of the magnitude of atrophy along the anterior-posterior axis of the hippocampus. Global hippocampal atrophy was observed in AD, with no discernible gradation or lateralisation. In contrast, SD patients displayed graded bilateral hippocampal atrophy, most pronounced on the left-hand side, and concentrated in anterior relative to posterior subregions. Finally, we found preliminary evidence that disease-specific vulnerability along the anterior-posterior axis of the hippocampus was associated with canonical clinical features of these syndromes.

Global hippocampal atrophy in major depressive disorder: a meta-analysis of magnetic resonance imaging studies.

Major depressive disorder (MDD), an incapacitating mental disorder, is characterized by episodes of at least 2 weeks of apparent changes in mood, cognition, and neurovegetative functions. Many neuroimaging studies using magnetic resonance imaging (MRI) have examined morphometric changes in patients with MDD, but the results are not conclusive. This study aims to review the literature and perform a meta-analysis on hippocampal volume (HcV) in patients with MDD. Studies on HcV in patients with MDD diagnosis were identified from major databases (MEDLINE, EMBASE, The Cochrane Library, Scopus, PsycINFO, and SciELO) using the search terms depression, major depressive disorder, MDD, unipolar, magnetic resonance imaging, MRI, and hippocampus. A meta-analysis of 29 studies fulfilling specific criteria was performed. The sample included 1327 patients and 1004 healthy participants. The studies were highly heterogeneous with respect to age, sex, age of onset, and average illness duration. However, the pooled effect size of depression was significant in both hippocampi. MDD was associated with right (-0.43; 95% confidence interval [95%CI] -0.66 to -0.21) and left (-0.40; 95%CI -0.66 to -0.15) hippocampal atrophy. MDD seems to be associated with global HcV atrophy. Larger longitudinal follow-up studies designed to analyze the influence of sociodemographic variables on this relationship are required to yield better evidence about this topic.

Hippocampal volume changes in patients with mood disorders

Due to the neurotoxic effect caused by high levels of cortisol, studies suggest that stress and certain psychiatric disorders, such as mood disorders, have influences under the hippocampus, causing a decrease in volume and consequent memory changes. Objective: evaluating the relationship between hippocampal volume in patients with mood disorders under therapy. Methodology: followed the PRISMA protocol for systematic reviews. Pubmed, Cochraine and Scielo databases were searched by terms "Hippocampus", "Mood Disorders" and "MRI", and variants in other languages, in human, from January 2011 to September 2016. The individual quality of the articles was analyzed using the Cochraine modified scale for clinical trials and the Agency for Healthcare Research and Quality scale for observational studies. All studies showed reduction of hippocampal volume in depressive patients. Change in hippocampal volume is not related to the use of antidepressant. Particularly the sub-region of the subculum is more reduced, without lateralizations. Significant relationship between stress and right hippocampal reduction. The findings seem to point out: a common pathway of hippocampus reduction, mediated by stress, explaining memory deficits due to depression, where the cortisol pathway seems to act; alteration in the prefrontal cortex; reduction in the subiculum related to inhibition of the hypothalamic-pituitary-adrenal axis, corroborating the hypothesis of cortisol. Conclusion: the papers suggest: association between global hippocampal atrophy with mood disorders; reduction of hippocampal subiculum; refractoriness to clinical treatment among patients with lower hippocampal volume.

Use of MRI to identify preclinical vascular dementia in symptomatic small vessel disease

BackgroundSporadic cerebral small vessel disease is an important cause of vascular dementia, and is a syndrome of cognitive impairment with evidence of vascular brain damage. At post-mortem examination pure vascular dementia is rare, with coexisting Alzheimer's disease pathology in 95% of cases. We aimed to use MRI to characterise the structural abnormalities during the preclinical phase of vascular dementia in symptomatic small vessel disease, and use these characteristics to accurately predict the development of future dementia. Methods121 adults with symptomatic small vessel disease were initially recruited to the St George's Cognition and Neuroimaging in Stroke (SCANS) study and followed up longitudinally for 5 years, with 22 individuals converting to dementia. Baseline T1-weighted MRI data were acquired for all 121 partcipants. Voxel-based morphometry was used to identify differences in patients with preclinical vascular dementia. Support vector machines were then used to predict future dementia from the baseline scans. Anatomical endophenotypes were defined using cluster ward linkage. FindingsWe found reduced grey matter density in the left striatum and hippocampus, and more white matter hyperintensities in the frontal white matter, in preclinical dementia. Future dementia could be predicted with a balanced accuracy of 73%. Four anatomical subtypes were identified. In one of them, patients were younger than those in the other three groups and had the highest levels of vascular damage; they also had milder cognitive impairment but rapid deterioration in processing speed and executive function, consistent with primary vascular dementia. The other groups had progressively less vascular damage and increasing memory impairment consistent with more Alzheimer's like pathology. The rates of hippocampal atrophy supported these groupings, with the vascular group resembling the cohort that did not develop dementia, and the Alzheimer's like group demonstrating more global hippocampal atrophy. InterpretationWe show that baseline MRI can reliably predict preclinical vascular dementia, with 73% of patients converting to dementia within 5 years. MRI can identify distinct anatomical endophenotypes representing a spectrum between vascular and Alzheimer's like pathology. This work provides a way to accurately stratify patients by use of a baseline MRI scan, and has utility in future clinical trials designed to slow or prevent the onset of dementia in these high-risk cohorts. FundingThe SCANS study was supported by the Wellcome Trust (grant 081589). Patient recruitment was supported by the National Institute for Health Research (NIHR) Clinical Stroke Research Network.

Micro-MRI Study of Cerebral Aging: Ex Vivo Detection of Hippocampal Subfield Reorganization, Microhemorrhages and Amyloid Plaques in Mouse Lemur Primates

Mouse lemurs are non-human primate models of cerebral aging and neurodegeneration. Much smaller than other primates, they recapitulate numerous features of human brain aging, including progressive cerebral atrophy and correlation between regional atrophy and cognitive impairments. Characterization of brain atrophy in mouse lemurs has been done by MRI measures of regional CSF volume and by MRI measures of regional atrophy. Here, we further characterize mouse lemur brain aging using ex vivo MR microscopy (31 µm in-plane resolution). First, we performed a non-biased, direct volumetric quantification of dentate gyrus and extended Ammon's horn. We show that both dentate gyrus and Ammon's horn undergo an age-related reorganization leading to a growth of the dentate gyrus and an atrophy of the Ammon's horn, even in the absence of global hippocampal atrophy. Second, on these first MR microscopic images of the mouse lemur brain, we depicted cortical and hippocampal hypointense spots. We demonstrated that their incidence increases with aging and that they correspond either to amyloid deposits or to cerebral microhemorrhages.

Subfield atrophy pattern in temporal lobe epilepsy with and without mesial sclerosis detected by high‐resolution MRI at 4 Tesla: Preliminary results

High-resolution magnetic resonance imaging (MRI) at 4 Tesla depicts details of the internal structure of the hippocampus not visible at 1.5 Tesla, and so allows for in vivo parcellation of different hippocampal subfields. The aim of this study was to test if distinct subfield atrophy patterns can be detected in temporal lobe epilepsy (TLE) with mesial temporal sclerosis (TLE-MTS) and without (TLE-no) hippocampal sclerosis. High-resolution T(2)-weighted hippocampal images were acquired in 34 controls: 15 TLE-MTS and 18 TLE-no. Entorhinal cortex (ERC), subiculum (SUB), CA1, CA2, and CA3, and dentate (CA3&DG) volumes were determined using a manual parcellation scheme. TLE-MTS had significantly smaller ipsilateral CA1, CA2, CA3&DG, and total hippocampal volume than controls or TLE-no. Mean ipsilateral CA1 and CA3&DG z-scores were significantly lower than ipsilateral CA2, ERC, and SUB z-scores. There were no significant differences between the various subfield or hippocampal z-scores on either the ipsi- or the contralateral side in TLE-no. Using a z-score <or=-2.0 to identify severe volume loss, the following atrophy patterns were found in TLE-MTS: CA1 atrophy, CA3&DG atrophy, CA1 and CA3&DG atrophy, and global hippocampal atrophy. Significant subfield atrophy was found in three TLE-no: contralateral SUB atrophy, bilateral CA3&DG atrophy, and ipsilateral ERC and SUB atrophy. Using a manual parcellation scheme on 4 Tesla high-resolution MRI, we found the characteristic ipsilateral CA1 and CA3&DG atrophy described in TLE-MTS. Seventeen percent of the TLE-no had subfield atrophy despite normal total hippocampal volume. These findings indicate that high-resolution MRI and subfield volumetry provide superior information compared to standard hippocampal volumetry.