Brain atrophy in normal ageing and Alzheimer's disease. Volumetric discrimination and clinical correlations

Serum Uric Acid Levels Associated with Outcomes of Neurodegenerative Disorders and Brain Health: Findings from the UK Biobank

BACKGROUND

The relationship between serum uric acid (SUA) levels and brain-related health remains uncertain.

OBJECTIVES

This study aimed to investigate the relationship between SUA levels and some neurodegenerative disorders and brain structure.

DESIGN

A longitudinal study.

SETTING AND PARTICIPANTS

384,517 participants who did not have stroke, dementia, and Parkinsonism, with complete urate testes and covariates were included.

MEASUREMENTS

Cox proportional hazards models, competing risk models, and restricted cubic spine models were applied.

RESULTS

During the median follow-up time of 12.7 years (interquartile range [IQR]:12.0, 13.5), 7821 (2.0%) participants developed stroke, 5103 (1.3%) participants developed dementia, and 2341 (0.6%) participants developed Parkinsonism. Nonlinear relationships were identified between SUA levels and stroke (J-shaped), dementia, and Parkinsonism (U-shaped). SUA levels of 4.2 mg/dl, 6.4 mg/dl, and 6.6 mg/dl yielded the lowest risk of stroke, dementia, and Parkinsonism, respectively. Besides, we found high SUA levels reduced the volumes of total brain, grey matter, white matter, grey matter in the hippocampus, and hippocampus, but increased lateral-ventricle volume. Inflammation accounted for 9.1% and 10.0% in the association of SUA with stroke and lateral-ventricle volume.

CONCLUSIONS

Lower SUA levels increased the risk of Parkinsonism, while both lower and higher SUA levels were positively associated with increased risk of stroke and dementia. Moreover, high SUA levels reduced brain structure volumes. Our findings suggest the association between SUA levels and brain-related disorders and highlight the importance of SUA management.

Navigating the intersection: Diabetes and Alzheimer's intertwined relationship

Alzheimer's disease (AD) and Diabetes mellitus (DM) exhibit comparable pathophysiological pathways. Genetic abnormalities in APP, PS-1, and PS-2 are linked to AD, with diagnostic aid from CSF and blood biomarkers. Insulin dysfunction, termed "type 3 diabetes mellitus" in AD, involves altered insulin signalling and neuronal shrinkage. Insulin influences beta-amyloid metabolism, exacerbating neurotoxicity in AD and amyloid production in DM. Both disorders display impaired glucose transporter expression, hastening cognitive decline. Mitochondrial dysfunction and Toll-like receptor 4-mediated inflammation worsen neurodegeneration in both diseases. ApoE4 raises disease risk, especially when coupled with dyslipidemia common in DM. Targeting shared pathways like insulin-degrading enzyme activation and HSP60 holds promise for therapeutic intervention. Recognizing these interconnected mechanisms underscores the imperative for developing tailored treatments addressing the overlapping pathophysiology of AD and DM, offering potential avenues for more effective management of both conditions.

Elevated Homocysteine Level and Brain Atrophy Changes as Markers to Screen the Alzheimer Disease: Case Series

Alzheimer disease (AD) is the most common cause of dementia worldwide. Its clinical manifestations include a progressive loss of memory and other cognitive domains, as well as brain atrophy. An elevated homocysteine level (>15 µmol/L), known as hyperhomocysteinemia, is also an attributing risk factor for AD, vascular pathologies, and brain atrophy. Neuroimaging studies including T2-weighted magnetic resonance imaging scans revealed white matter hyperintensities in the periventricular and deep white matter, enlarged ventricles, widened sulci, and decreased white matter mass, which are features of aging, as well as cerebrovascular changes. This case series investigated changes in biochemical marker levels including serum homocysteine, folate, and vitamin B12, and the degree of atrophic variations in cortical-subcortical white matter in AD. The present study hypothesized that serum homocysteine levels might be used as a surrogate marker to screen for AD at an earlier stage.

A Rare Pediatric Neurological Case: Dyke-Davidoff-Masson Syndrome Unprecedented at 10 Months

This case report presents a rare occurrence of Dyke-Davidoff-Masson Syndrome (DDMS) in a 10-month-old male child, highlighting the atypical presentation of this neurological disorder in early infancy. The child initially presented with irritability, loss of appetite, and right-sided weakness following episodes of fever. A comprehensive medical history revealed the sudden onset of generalized tonic-clonic seizures, prompting further investigation. Diagnostic imaging, including CT and MRI, confirmed features consistent with DDMS, including cerebral hemiatrophy, ventricular enlargement, and calvarial thickening. Notably, the child's seizures were successfully managed with antiepileptic medication, leading to stabilized vital signs. This case emphasizes the importance of considering rare neurological disorders in pediatric patients with unusual presentations and underscores the challenges in diagnosing and managing DDMS in infancy. Further research is warranted to elucidate the underlying mechanisms, contributing factors, and optimal management strategies for DDMS in this age group.

Impact of ectopic fat on brain structure and cognitive function:A systematic review and meta-analysis from observational studies

Ectopic fat, defined as a specific organ or compartment with the accumulation of fat tissue surrounding organs, is highly associated with obesity which has been identified as a risk factor for cognitive impairment and dementia. However, the relationship between ectopic fat and changes in brain structure or cognition is yet to be elucidated. Here, we investigated the effects of ectopic fat on brain structure and cognitive function via systemic review and meta-analysis. A total of 22 studies were included, encompassing 1,003,593 participants-obtained from electronic databases up to July 9, 2022. We found ectopic that fat was associated with decreased total brain volume and increased lateral ventricle volume. In addition, ectopic was associated with decreased cognitive scores and negatively correlated with cognitive function. More specifically, dementia development was correlated with increased levels of visceral fat. Overall, our data suggest that increased ectopic fat is associated with prominent structural changes in the brain and cognitive decline, an effect driven mainly by increases in visceral fat, while subcutaneous fat may be protective. Our results suggest that patients with increased visceral fat are at risk of developing cognitive impairment and, therefore, represent a subset of population in whom appropriate and timely preventive measures could be implemented.

Smaller spared subcortical nuclei are associated with worse post-stroke sensorimotor outcomes in 28 cohorts worldwide

Up to two-thirds of stroke survivors experience persistent sensorimotor impairments. Recovery relies on the integrity of spared brain areas to compensate for damaged tissue. Deep grey matter structures play a critical role in the control and regulation of sensorimotor circuits. The goal of this work is to identify associations between volumes of spared subcortical nuclei and sensorimotor behaviour at different timepoints after stroke. We pooled high-resolution T1-weighted MRI brain scans and behavioural data in 828 individuals with unilateral stroke from 28 cohorts worldwide. Cross-sectional analyses using linear mixed-effects models related post-stroke sensorimotor behaviour to non-lesioned subcortical volumes (Bonferroni-corrected, P < 0.004). We tested subacute (≤90 days) and chronic (≥180 days) stroke subgroups separately, with exploratory analyses in early stroke (≤21 days) and across all time. Sub-analyses in chronic stroke were also performed based on class of sensorimotor deficits (impairment, activity limitations) and side of lesioned hemisphere. Worse sensorimotor behaviour was associated with a smaller ipsilesional thalamic volume in both early (n = 179; d = 0.68) and subacute (n = 274, d = 0.46) stroke. In chronic stroke (n = 404), worse sensorimotor behaviour was associated with smaller ipsilesional putamen (d = 0.52) and nucleus accumbens (d = 0.39) volumes, and a larger ipsilesional lateral ventricle (d = -0.42). Worse chronic sensorimotor impairment specifically (measured by the Fugl-Meyer Assessment; n = 256) was associated with smaller ipsilesional putamen (d = 0.72) and larger lateral ventricle (d = -0.41) volumes, while several measures of activity limitations (n = 116) showed no significant relationships. In the full cohort across all time (n = 828), sensorimotor behaviour was associated with the volumes of the ipsilesional nucleus accumbens (d = 0.23), putamen (d = 0.33), thalamus (d = 0.33) and lateral ventricle (d = -0.23). We demonstrate significant relationships between post-stroke sensorimotor behaviour and reduced volumes of deep grey matter structures that were spared by stroke, which differ by time and class of sensorimotor measure. These findings provide additional insight into how different cortico-thalamo-striatal circuits support post-stroke sensorimotor outcomes.

Head CT: Toward Making Full Use of the Information the X-Rays Give

Although clinical head CT images are typically interpreted qualitatively, automated methods applied to routine clinical head CTs enable quantitative assessment of brain volume, brain parenchymal fraction, brain radiodensity, and brain radiomass. These metrics gain clinical meaning when viewed relative to a reference database and expressed as quantile regression values. Quantitative imaging data can aid in objective reporting and in the identification of outliers, with possible diagnostic implications. The comparison to a reference database necessitates standardization of head CT imaging parameters and protocols. Future research is needed to learn the effects of virtual monochromatic imaging on the quantitative characteristics of head CT images.

Theoretical impact of the AT(N) framework on dementia using a community autopsy sample

The AT(N) research framework categorizes eight biomarker profiles using amyloid (A), tauopathy (T), and neurodegeneration (N), regardless of dementia status. We evaluated associations with dementia risk in a community-based cohort by approximating AT(N) profiles using autopsy-based neuropathology correlates, and considered cost implications for clinical trials for secondary prevention of dementia based on AT(N) profiles. We used Consortium to Establish a Registry for Alzheimer's Disease (moderate/frequent) to approximate A+, Braak stage (IV-VI) for T+, and temporal pole lateral ventricular dilation for (N)+. Outcomes included dementia prevalence at death and incidence in the last 5 years of life. A+T+(N)+ was the most common profile (31%). Dementia prevalence ranged from 14% (A-T-[N]-) to 79% (A+T+[N]+). Between 8% (A+T-[N]-) and 68% (A+T+[N]-) of decedents developed incident dementia in the last 5 years of life. Clinical trials would incur substantial expense to characterize AT(N). Many people with biomarker-defined preclinical Alzheimer's disease will never develop clinical dementia during life, highlighting resilience to clinical expression of AD neuropathologic changes and the need for improved tools for prediction beyond current AT(N) biomarkers.

Quantitative susceptibility mapping as an indicator of subcortical and limbic iron abnormality in Parkinson's disease with dementia

Late stage Parkinson's disease (PD) patients were commonly observed with other non-motor comorbidities such as dementia and psychosis. While abnormal iron level in the substantia nigra was clinically accepted as a biomarker of PD, it was also suggested that the increased iron deposition could impair other brain regions and induce non-motor symptoms. A new Magnetic Resonance Imaging (MRI) called Quantitative Susceptibility Mapping (QSM) has been found to measure iron concentration in the grey matter reliably. In this study, we investigated iron level of different subcortical and limbic structures of Parkinson's disease (PD) patients with and without dementia by QSM. QSM and volumetric analysis by MRI were performed in 10 PD dementia (PDD) patients (73 ± 6 years), 31 PD patients (63 ± 8 years) and 27 healthy controls (62 ± 7 years). No significant differences were observed in the L-Dopa equivalent dosage for the two PD groups (p = 0.125). Putative iron content was evaluated in different subcortical and limbic structures of the three groups, as well as its relationship with cognitive performance. One-way ANCOVA with FDR adjustment at level of 0.05, adjusted for age and gender, showed significant group differences for left and right hippocampus (p = 0.015 & 0.032, respectively, BH-corrected for multiple ROIs) and right thalamus (p = 0.032, BH-corrected). Post-hoc test with Bonferroni's correction suggested higher magnetic susceptibility in PDD patients than healthy controls in the left and right hippocampus (p = 0.001 & 0.047, respectively, Bonferroni's corrected), while PD patients had higher magnetic susceptibility than the healthy controls in right hippocampus and right thalamus (p = 0.006 & 0.005, respectively, Bonferroni's corrected). PDD patients also had higher susceptibility than the non-demented PD patients in left hippocampus (p = 0.046, Bonferroni's corrected). The magnetic susceptibilities of the left and right hippocampus were negatively correlated with the Mini-Mental State Examination score (r = -0.329 & -0.386, respectively; p < 0.05). This study provides support for iron accumulation in limbic structures of PDD and PD patients and its correlation with cognitive performance, however, its putative involvement in development of non-motor cognitive dysfunction in PD pathogenesis remains to be elucidated.

Brain structural investigation and hippocampal tractography in medication overuse headache: a native space analysis

BACKGROUND

Spatial normalization of brain images, a prerequisite for voxel based morphometry analysis, may account for the large variability of the volumetric data in medication overuse headache (MOH); possibly because this disease concerns patients differing on both sex and age, and hence with different brain size and shape.

METHODS

The present study aimed at providing a subject-based analysis of macrostructure using a native space volumes segmentation (Freesurfer), and microstructure using a region of interest (ROI: i.e. hippocampus) tractography approach in MOH patients.

RESULTS

The results show that MOH patients had decreased volumes of left hemisphere temporal gyri (temporal superior, fusiform) and occipital middle gyrus, together with an increased volume of the left inferior (temporal) lateral ventricle. The left temporal volume was negatively correlated with depression score and medication dependence parameters. Seed-based tractography of the hippocampus revealed a decreased number of reconstructed fibers passing through the left hippocampus.

CONCLUSION

To our knowledge, these alterations have not been described with methods involving brain normalization, and they indicate that left hemisphere temporal areas, including the hippocampus, may play a role in MOH pathophysiology. Trial registration number NCT00833209. Registered 29 January 2009.

MRI-Based Neuroanatomical Predictors of Dysphagia, Dysarthria, and Aphasia in Patients with First Acute Ischemic Stroke

Background

Due to the high post-stroke frequency of dysphagia, dysarthria, and aphasia, we developed comprehensive neuroanatomical, clinical, and demographic models to predict their presence after acute ischemic stroke.

Methods

The sample included 160 randomly selected first-ever stroke patients with confirmed infarction on magnetic resonance imaging from 1 tertiary stroke center. We documented acute lesions within 12 neuroanatomical regions and their associated volumes. Further, we identified concomitant chronic brain disease, including atrophy, white matter hyperintensities, and covert strokes. We developed predictive models using logistic regression with odds ratios (OR) and their 95% confidence intervals (95% CI) including demographic, clinical, and acute and chronic neuroanatomical factors.

Results

Predictors of dysphagia included medullary (OR 6.2, 95% CI 1.5–25.8), insular (OR 4.8, 95% CI 2.0–11.8), and pontine (OR 3.6, 95% CI 1.2–10.1) lesions, followed by brain atrophy (OR 3.0, 95% CI 1.04–8.6), internal capsular lesions (OR 2.9, 95% CI 1.2–6.6), and increasing age (OR 1.4, 95% CI 1.1–1.8). Predictors of dysarthria included pontine (OR 7.8, 95% CI 2.7–22.9), insular (OR 4.5, 95% CI 1.8–11.4), and internal capsular (OR 3.6, 95% CI 1.6–7.9) lesions. Predictors of aphasia included left hemisphere insular (OR 34.4, 95% CI 4.2–283.4), thalamic (OR 6.2, 95% CI 1.6–24.4), and cortical middle cerebral artery (OR 4.7, 95% CI 1.5–14.2) lesions.

Conclusion

Predicting outcomes following acute stroke is important for treatment decisions. Determining the risk of major post-stroke impairments requires consideration of factors beyond lesion localization. Accordingly, we demonstrated interactions between localized and global brain function for dysphagia and elucidated common lesion locations across 3 debilitating impairments.

Impact of Long-Term Endurance Training vs. Guideline-Based Physical Activity on Brain Structure in Healthy Aging

Brain structure is a fundamental determinant of brain function, both of which decline with age in the adult. Whereas short-term exercise improves brain size in older adults, the impact of endurance training on brain structure when initiated early and sustained throughout life, remains unknown. We tested the hypothesis that long-term competitive aerobic training enhances cortical and subcortical mass compared to middle to older-aged healthy adults who adhere to the minimum physical activity guidelines. Observations were made in 16 masters athletes (MA; 53 ± 6 years, VO_2max = 55 ± 10 ml/kg/min, training > 15 years), and 16 active, healthy, and cognitively intact subjects (HA; 58 ± 9 years, VO_2max = 38 ± 7 ml/kg/min). T1-weighted structural acquisition at 3T enabled quantification of cortical thickness and subcortical gray and white matter volumes. Cardiorespiratory fitness correlated strongly with whole-brain cortical thickness. Subcortical volumetric mass at the lateral ventricles, R hippocampus, R amygdala, and anterior cingulate cortex, correlated with age but not fitness. In a region-of-interest (ROI) group-based analysis, MA expressed greater cortical thickness in the medial prefrontal cortex, pre and postcentral gyri, and insula. There was no effect of group on the rate of age-related cortical or subcortical decline. The current data suggest that lifelong endurance training that produces high levels of cardiorespiratory fitness, builds cortical reserve early in life, and sustains this benefit over the 40–70 year age span. This reserve likely has important implications for neurological health later in life.

Jugular venous reflux and brain parenchyma volumes in elderly patients with mild cognitive impairment and Alzheimer's disease

BACKGROUND

To determine whether or not jugular venous reflux (JVR) is associated with structural brain parenchyma changes in individuals with mild cognitive impairment (MCI) and Alzheimer's disease (AD).

METHODS

16 AD patients (mean (SD): 81.9 (5.8) years), 33 MCI patients (mean (SD): 81.4 (6.1) years) and 18 healthy elderly controls (mean (SD): 81.5 (3.4) years) underwent duplex ultrasonography and magnetic resonance imaging scans to quantify structural brain parenchyma changes. Normalized whole brain (WB), gray matter (GM) and white matter (WM) volumes were collected, together with CSF volume.

RESULTS

JVR was strongly associated with increased normalized WB (p = 0.014) and GM (p = 0.002) volumes across all three subject groups. There was a trend towards increased WB and GM volumes, which was accompanied by decreased CSF volume, in the JVR-positive subjects in both the MCI and AD groups. When the MCI and AD subjects were aggregated together significant increases were observed in both normalized WB (p = 0.009) and GM (p = 0.003) volumes for the JVR-positive group. No corresponding increases were observed for the JVR-positive subjects in the control group. Through receiver operating characteristic analysis of the brain volumetric data it was possible to discriminate between the JVR-positive and negative AD subjects with reasonable accuracy (sensitivity = 71.4%; specificity = 88.9%; p = 0.007).

CONCLUSIONS

JVR is associated with intracranial structural changes in MCI and AD patients, which result in increased WB and GM volumes. The neuropathology of this unexpected and counterintuitive finding requires further investigation, but may suggest that JVR retrogradely transmits venous hypertension into the brain and leads to brain tissues swelling due to vasogenic edema.

Accelerated cognitive decline in patients with type 2 diabetes: MRI correlates and risk factors

BACKGROUND

Type 2 diabetes mellitus is associated with an increased risk of cognitive decline and dementia. We examined brain imaging correlates and vascular and metabolic risk factors of accelerated cognitive decline in patients with type 2 diabetes.

METHODS

Cognitive functioning and brain volume as well as metabolic and vascular risk factors were assessed twice in 68 patients with no dementia with type 2 diabetes with a 4-year interval. Thirty-eight control participants served as a reference group. Volumetric measurements of the total brain, lateral ventricles and white-matter hyperintensities were performed on 1.5T magnetic resonance imaging scans. A regression-based index score was calculated on the basis of the reference group to assess changes in cognitive performance over time, adjusted for age, sex and estimated intelligence quotient. Brain volumes were compared between patients with and without accelerated cognitive decline. Logistic regression analyses were used to identify baseline risk factors for accelerated cognitive decline within the diabetes group.

RESULTS

Accelerated cognitive decline was found in 17 (25%) patients with type 2 diabetes and was associated with a greater increase in ventricular volume [mean difference (95% confidence interval): 0.23% (0.08-0.38); p = 0.003] and white-matter hyperintensities volume [0.16% (0.05-0.27); p = 0.006] over the 4-year period. There were no specific vascular or metabolic risk factors associated with accelerated cognitive decline.

CONCLUSIONS

Accelerated cognitive decline in patients with type 2 diabetes was associated with progressive changes on brain magnetic resonance imaging, comprising both vascular damage and global atrophy. Exploration of vascular and metabolic risk factors revealed no specific determinants of accelerated cognitive decline.

Generalized cerebral atrophy seen on MRI in a naturally exposed animal model for Creutzfeldt-Jakob disease

BACKGROUND

Magnetic resonance imaging has been used in the diagnosis of human prion diseases such as sCJD and vCJD, but patients are scanned only when clinical signs appear, often at the late stage of disease. This study attempts to answer the questions "Could MRI detect prion diseases before clinical symptoms appear?, and if so, with what confidence?"

METHODS

Scrapie, the prion disease of sheep, was chosen for the study because sheep can fit into a human sized MRI scanner (and there were no large animal MRI scanners at the time of this study), and because the USDA had, at the time of the study, a sizeable sample of scrapie exposed sheep, which we were able to use for this purpose. 111 genetically susceptible sheep that were naturally exposed to scrapie were used in this study.

RESULTS

Our MRI findings revealed no clear, consistent hyperintense or hypointense signal changes in the brain on either clinically affected or asymptomatic positive animals on any sequence. However, in all 37 PrPSc positive sheep (28 asymptomatic and 9 symptomatic), there was a greater ventricle to cerebrum area ratio on MRI compared to 74 PrPSc negative sheep from the scrapie exposed flock and 6 control sheep from certified scrapie free flocks as defined by immunohistochemistry (IHC).

CONCLUSIONS

Our findings indicate that MRI imaging can detect diffuse cerebral atrophy in asymptomatic and symptomatic sheep infected with scrapie. Nine of these 37 positive sheep, including 2 one-year old animals, were PrPSc positive only in lymph tissues but PrPSc negative in the brain. This suggests either 1) that the cerebral atrophy/neuronal loss is not directly related to the accumulation of PrPSc within the brain or 2) that the amount of PrPSc in the brain is below the detectable limits of the utilized immunohistochemistry assay. The significance of these findings remains to be confirmed in human subjects with CJD.

Callosal microstructural abnormalities in Alzheimer's disease and alcoholism: same phenotype, different mechanisms

Magnetic resonance (MRI) and diffusion tensor imaging (DTI) data were acquired in 13 Alzheimer's disease (AD) patients, 15 elderly alcoholics, and 32 elderly controls. Midsagittal area, length, dorsoventral height, fractional anisotropy (FA), and mean diffusivity (MD) of the total corpus callosum and volume of the lateral ventricles were measured; area, FA, and MD were also determined for the callosal genu, body, and splenium. On DTI, both patient groups had lower FA and higher MD than controls in all callosal regions. On MRI, both patient groups had smaller genu than controls; additional size deficits were present in the alcoholism group's callosal body and the AD group's splenium. The callosal arch was higher in the AD but not the alcoholic group compared with controls. The two patient groups had larger ventricles than controls, and the AD group had larger ventricles than the alcoholic group. Callosal area correlated with its height, and callosal FA and MD correlated with ventricular volume in AD, whereas callosal area correlated only with FA in alcoholics. In AD, the disruption of the callosal integrity, which was associated with distorted callosal shape, was related to ventricular dilation, which has been shown in twin studies to be under a multitude of genetic, polygenetic, and environmental influences. Conversely, in alcoholism, disruption of callosal microstructural integrity was related to shrinkage of the corpus callosum itself.

[Stereology as a tool to estimate brain volume and cortical atrophy in elders with dementia]

INTRODUCTION

stereology is a body of methods that allow unbiased and efficient estimation of geometric quantities defined in arbitrary physical structures. In particular, stereology is a valuable tool to assist neuroimaging in the estimation of morphometric parameters in the brain. Therefore, stereology may confer objectivity in the complementary and diagnostic evaluation of dementia by adding disease by adding quantitative data to clinical evaluation.

OBJECTIVES AND METHODS

our purpose was to illustrate estimation of brain volume and pial surface area by means of quantitative, computer-assisted stereological methods. Both parameters were estimated by means of a vertical design with a single series of parallel Cavalieri sections at a random orientation and perpendicular to a fixed horizontal plane. The sections were obtained by magnetic resonance imaging. Suitable test systems (of test points for volume, and of cycloids for surface area) were superimposed on these sections with the aid of special software.

RESULTS

to explore the statistical error of the volume estimator due to stereological sampling, 5 or 10 systematic sections were used in combination with two test point densities in a ratio of 1:4, so that the workload varied in the proportions 1:2:4:8. The four resulting estimators varied between 986 and 1120 cm(3). The surface area estimators varied between 1947 and 2096 cm(2), with workloads varying in the proportions of 1:2:2.3:4.6.

CONCLUSIONS

stereology is a simple and efficient tool to obtain objective brain volume and surface area estimators that are unbiased by design and accurate at a modest cost. Thus the corresponding methods can effectively assist in diagnostic and follow-up evaluation of elders with dementia.

Comparison of Three Methods for the Estimation of Total Intracranial Volume

There is a well-known close relationship between the total intracranial volume (TIV) and the brain size. Several studies in different countries have estimated the cranial capacity, which indirectly reflects the brain volume. However, we have not seen a study evaluating the results of the methodologies for the assessment of TIV. This study was carried out on 30 normal subjects whose ages ranged between 19 and 77 years old (males, 18; females, 12). Three different methods were used to assess the TIV. The mean (+/-SD) estimated TIV using linear dimensions method in males and females were 1416.8 +/- 64 cm and 1291.9 +/- 152 cm, respectively. The mean estimated TIV using point counting method in males and females was 1474 +/- 93 cm and 1252 +/- 72 cm, respectively. By using the planimetric method of the mean and SD of TIV, male and females were 1492.1 +/- 74 cm and 1319.6 +/- 100 cm, respectively. There were no statistical difference between TIV measurements obtained using the optimized stereologic technique and planimetry (P > 0.05). TIV between males and females was statistically significant (P < 0.001). This study showed that there are minor differences among the given 3 distinct methods. With the disadvantage of requiring more time to apply, the planimetry and point counting methods provide more assumption-free results than the anthropometric approach. However, the anthropometric method can be applied to assess TIV without needing sophisticated tools.

Brain lesions on MRI and endogenous sex hormones in elderly men

We investigated the association between MRI detected brain lesions and levels of endogenous sex hormones in Japanese-American men aged 74-95 years. Logistic regression was used to estimate the association (OR (95% CI)) of MRI outcome with tertiles of bioavailable testosterone, 17beta estradiol and sex hormone binding globulin (SHBG). There was a significantly increased risk for cerebral atrophy in the highest tertile of testosterone (3.1 (1.2-7.8)) compared to the lowest. We also found that men with the highest estradiol had a higher risk of lacunes (1.92 (1.1-3.2)). These relationships did not change with adjustment for the other sex hormones, cardiovascular risk factors, or other brain lesions. In contrast, men with the highest SHBG had a lower risk both of cerebral atrophy and lacunes, after adjusting for sex hormones and cardiovascular risk factors. There were no associations between sex hormones and hippocampal atrophy, white matter lesions, and large infarcts. Because the levels of hormone were measured close in time to the acquisition of the MRI, these associations may reflect neurodegeneration in brain regions regulating hormone levels.

Episodic-like memory deficits in the APPswe/PS1dE9 mouse model of Alzheimer's disease: relationships to beta-amyloid deposition and neurotransmitter abnormalities

Transgenic mice made by crossing animals expressing mutant amyloid precursor protein (APPswe) to mutant presenilin 1 (PS1dE9) allow for incremental increases in Abeta42 production and provide a model of Alzheimer-type amyloidosis. Here, we examine cognition in 6- and 18-month old transgenic mice expressing APPswe and PS1dE9, alone and in combination. Spatial reference memory was assessed in a standard Morris Water Maze task followed by assessment of episodic-like memory in Repeated Reversal and Radial Water maze tasks. We then used factor analysis to relate changes in performance in these tasks with cholinergic markers, somatostatin levels, and amyloid burden. At 6 months of age, APPswe/PS1dE9 double-transgenic mice showed visible plaque deposition; however, all genotypes, including double-transgenic mice, were indistinguishable from nontransgenic animals in all cognitive measures. In the 18-month-old cohorts, amyloid burdens were much higher in APPswe/PS1dE9 mice with statistically significant but mild decreases in cholinergic markers (cortex and hippocampus) and somatostatin levels (cortex). APPswe/PS1dE9 mice performed all cognitive tasks less well than mice from all other genotypes. Factor and correlation analyses defined the strongest correlation as between deficits in episodic-like memory tasks and total Abeta loads in the brain. Collectively, we find that, in the APPswe/PS1dE9 mouse model, some form of Abeta associated with amyloid deposition can disrupt cognitive circuits when the cholinergic and somatostatinergic systems remain relatively intact; and that episodic-like memory seems to be more sensitive to the toxic effects of Abeta.

Structural correlates of mild cognitive impairment

The structural correlates of mild cognitive impairment (MCI) were examined in 105 elderly subjects whose cognitive function ranged from intact to demented, including 38 subjects with MCI. Hippocampal volumes (left and right HcV), brain volume (BV), and grey matter volume (GMV) and white matter volume (WMV) were segmented from high resolution magnetic resonance data sets and normalised to intracranial volume (ICV). Hippocampal volume reductions, but not global brain, white or grey matter atrophy, were associated with MCI. White matter lesion severity did not differ over cognitive states. In multiple logistic regression models, normalised HcV and ICV (indicating premorbid brain volume) were significant predictors of MCI versus normality. Normalised BV and ICV significantly predicted dementia versus MCI. Absolute volumetric measures of HcV and BV yielded comparable classification accuracies. Hippocampal atrophy may be the crucial step for the transition from normality to MCI. Widespread brain atrophy may be the step to determine the transition from MCI to dementia. Brain volume reserve effects appear to be involved in both of these steps.

Role of white matter lesions, cerebral atrophy, and APOE on cognition in older persons with and without dementia: the Cache County, Utah, study of memory and aging

Neuropsychological, qualitative, and quantitative magnetic resonance imaging findings were examined in subjects with Alzheimer's disease (AD), non-AD dementia or mixed neuropsychiatric disorder, subjects characterized as mild/ambiguous, and controls, all with known apolipoprotein E (APOE) genotype. Neuropsychological tasks included an expanded Consortium to Establish a Registery for Alzheimer's Disease (J. T. Tschanz et al., 2000; K. A. Welsh, J. M. Hoffman, N. L. Earl, & M. W. Hanson 1994) battery and the Mini-Mental Status Examination (M. F. Folstein, S. E. Folstein, & P. R. McHugh, 1975). Periventricular white matter lesions were the most clinically salient, and generalized measures of cerebral atrophy were the most significant quantitative indicators. APOE genotype was unrelated to imaging or neuropsychological performance. Neuropsychological relationships with neuroimaging findings depend on the qualitative or quantitative method used.

Utility of simultaneous brain, CSF and hyperintensity quantification in dementia

Improved methods of quantifying MRI are needed to study brain-behavior relationships in dementia. Rating scales are variable; lesion-tracing approaches can be subjective and ignore atrophy; segmentation of MRI hyperintensities is complicated by partial volume effects; and hyperintense lesions in different anatomical areas may have different effects. The goal of this study was to extend existing segmentation approaches to include hyperintensities and to demonstrate the utility of simultaneously assessing atrophy and lesion compartments in dementia. A semi-automated method was applied to quantify brain and cerebrospinal fluid (CSF) compartments and to subclassify hyperintensities into periventricular, deep white matter, thalamic and basal ganglia compartments. Twenty MR scans from participants in an ongoing dementia study were used to generate intra- and inter-rater reliability estimates. High intra- and inter-class correlation coefficients (0.83-0.99) were obtained for all measures and the semi-automated measurements were highly correlated with traced volumes. Brain, CSF and specific lesion volumes were significantly correlated with neuropsychological functions. In models using only total hyperintensity volumes, the effects of lesion compartments (such as thalamic) were masked. Simultaneous quantification of atrophy and anatomically distinct hyperintensities is important for understanding cognitive impairments in dementia.

Whole brain segmentation: automated labeling of neuroanatomical structures in the human brain

We present a technique for automatically assigning a neuroanatomical label to each voxel in an MRI volume based on probabilistic information automatically estimated from a manually labeled training set. In contrast to existing segmentation procedures that only label a small number of tissue classes, the current method assigns one of 37 labels to each voxel, including left and right caudate, putamen, pallidum, thalamus, lateral ventricles, hippocampus, and amygdala. The classification technique employs a registration procedure that is robust to anatomical variability, including the ventricular enlargement typically associated with neurological diseases and aging. The technique is shown to be comparable in accuracy to manual labeling, and of sufficient sensitivity to robustly detect changes in the volume of noncortical structures that presage the onset of probable Alzheimer's disease.

MR image-based measurement of rates of change in volumes of brain structures. Part II: application to a study of Alzheimer's disease and normal aging

We present global and regional rates of brain atrophy measured on serially acquired T1-weighted brain MR images for a group of Alzheimer's disease (AD) patients and age-matched normal control (NC) subjects using the analysis procedure described in Part I. Three rates of brain atrophy: the rate of atrophy in the cerebrum, the rate of lateral ventricular enlargement and the rate of atrophy in the region of temporal lobes, were evaluated for 14 AD patients and 14 age-matched NC subjects. All three rates showed significant differences between the two groups. However, the greatest separation of the two groups was obtained when the regional rates were combined. This application has demonstrated that rates of brain atrophy, especially in specific regions of the brain, based on MR images can provide sensitive measures for evaluating the progression of AD. These measures will be useful for the evaluation of therapeutic effects of novel therapies for AD.

Brain ageing in the new millennium

OBJECTIVE

This paper examines the current literature pertaining to brain ageing. The objective of this review is to provide an overview of the effects of ageing on brain structure and function and to examine possible mediators of these changes.

METHODS

A MEDLINE search was conducted for each area of interest. A selective review was undertaken of relevant articles.

RESULTS

Although fundamental changes in fluid intellectual abilities occur with age, global cognitive decline is not a hallmark of the ageing process. Decline in fluid intellectual ability is paralleled by regionally specific age related changes apparent from both structural and functional neuroimaging studies. The histopathological mediators of these changes do not appear to be reduction in neuronal number, which, with the exception of selected hippocampal regions, remain relatively stable across age. At the molecular level, several mechanisms of age related change have been postulated. Such theoretical models await refinement and may eventually provide a basis for therapy designed to reduce effects of the ageing process. The role of possible protective factors such as 'brain reserve', neuroprotective agents and hormonal factors in modifying individual vulnerability to the ageing process has been the focus of a limited number of studies.

CONCLUSION

Our understanding of the functional and structural changes associated with both healthy and pathological ageing is rapidly gaining in sophistication and complexity. An awareness of the fundamental biological substrates underpinning the ageing process will allow improved insights into vulnerability to neuropsychiatric disease associated with advancing age.

Dual voxel proton magnetic resonance spectroscopy in the healthy elderly: subcortical-frontal axonal N-acetylaspartate levels are correlated with fluid cognitive abilities independent of structural brain changes

The published literature suggests that degeneration of the subcorticofrontal networks may underlie cognitive ageing, but appropriate methods to examine this in vivo have been lacking. Proton Magnetic Resonance Spectroscopy ((1)H-MRS) has now been used in a number of clinical studies to assess cerebral pathophysicochemistry and recently has been utilized to examine the relationship between neurochemical markers and cognitive functioning in normal individuals. Results have been somewhat conflicting and difficult to interpret. To further clarify the role of the cognitive spectroscopy technique, we measured N-acetylaspartate (NAA) levels in the frontal subcortical white matter and the occipitoparietal grey matter and correlated them with performance in different cognitive domains in a group of twenty healthy elderly individuals. Subjects underwent whole brain T(1)- and T(2)-weighted magnetic resonance imaging (MRI), dual voxel short echo-time (1)H-MRS, and a comprehensive neuropsychological assessment. Individual tests of executive and attentional abilities, and a principal components composite score reflecting these skills, but not measures of memory or verbal abilities, were correlated with NAA concentration in the frontal white matter only. These relationships were independent of other neurocognitive predictors of executive impairment such as age, midventricular dilation, frontal white matter disease, and presenescent verbal proficiency. This study suggests the ability of (1)H-MRS to differentiate anatomically distinct neurochemical markers related to specific cognitive abilities. In particular, neurometabolic fitness of the frontal subcortical-cortical axonal fibers may be important in mediating fluid intellectual processing. Longitudinal MRS studies are required to determine if the present results reflect different rates of neurocellular degeneration or preexisting individual differences in neuronal density.

A retrospective study of neuroradiological abnormalities detected on structural magnetic resonance imaging of the brain in elderly patients with cognitive impairment

BACKGROUND

The aim of the study was to investigate the relationship between neuroradiological and clinical diagnosis in patients presenting with cognitive impairment, and also the relationship between the neuroradiological abnormalities and cognitive function as assessed by the Mini-Mental State Examination (MMSE) score.

METHODS

One hundred and four elderly subjects (65 years and over) with cognitive impairment, referred to secondary hospital services and who had brain magnetic resonance imaging (MRI) scans as part of routine clinical investigations, were studied by review of their MRI scans using a standardized procedure and by examination of the case notes.

RESULTS

In patients with a clinical diagnosis of senile dementia Alzheimer-type (SDAT), the diagnosis was reviewed in 11.1%. In patients with vascular dementia, the diagnosis was reviewed in 62. 5%. In patients without a firm clinical diagnosis, radiological features compatible with SDAT were seen in 44.4% and with vascular dementia in 27.0%. Only 2/104 patients showed a significant focal lesion on MRI. Of the variables studied (age, sex, degree of hippocampal atrophy, extent of T2 hyper-intensities, and enlargement of the sulcal and ventricular cerebrospinal fluid (CSF) spaces) only hippocampal atrophy predicted the MMSE score ( p < 0.002).

CONCLUSION

MRI brain scanning has an important role in aiding and refining the clinical diagnosis of cognitive impairment/dementia in the elderly.

Clinical issues in current drug therapy for dementia

Dementia resulting from Alzheimer disease is one of the most prevalent medical problems. Elaborate expert guidelines for the diagnosis and treatment of Alzheimer disease do not always take sufficient account of the resources available in general practice. The focus on pure Alzheimer disease can be inappropriate for the large proportion of mixed dementia cases in old age. Because of such guidelines, treatment with modern and effective drugs is often delayed until conservative dementia criteria are satisfied. Criteria for the discontinuation of antidementia drugs are highly questionable. Antidementia drug sales in Germany demonstrate that the majority of prescribers hold on to conservative attitudes and prefer Ginkgo biloba and memantine to acetylcholinesterase inhibitors. Disappointment after exaggerated expectations and financial restrictions in the health care sector may aggravate current underprescribing of antidementia drugs. Even though contemporary symptomatic treatments for Alzheimer disease are unsatisfactory, modern medicine has been very successful in the early diagnosis and treatment of other potential causes of dementia. Future strategies will include models for the early identification of individuals carrying a high risk of developing cognitive impairment during their lifetime.

Estrogen replacement therapy and MRI-demonstrated cerebral infarcts, white matter changes, and brain atrophy in older women: the Cardiovascular Health Study

OBJECTIVE

We studied the relationship between the use of estrogen replacement therapy (ERT) and cerebral magnetic resonance imaging (MRI) abnormalities among older women.

DESIGN

A population-based prospective study (Cardiovascular Health Study).

SETTING

Four regions in the United States.

PARTICIPANTS

A total of 2133 (62.9% of the eligible) women aged 65 to 95 years (mean age 74.8), on whom MRI was performed in 1992-1994.

MEASUREMENTS

Presence of global brain atrophy, white matter changes, small infarct-like lesion (ILL) (<3 mm), MRI infarcts (> or =3 mm, mostly small and asymptomatic), and cognitive function as measured by Mini-Mental State Exam (MMSE), and by ERT use (current/past/never), adjusted for a number of socioeconomic, lifestyle, and reproductive covariates.

RESULTS

Current use of ERT was reported by 15% and past use by another 23% of participants; 35% of all women had MRI infarcts. The prevalence of MRI infarcts did not differ in current or past users from those who had never used ERT (nonusers). Bifrontal distance, the largest distance between frontal horns, and the size of ventricles were larger among current ERT users compared to past users or nonusers (P (trend) = .01), adjusted for all other covariates, but no dose-response relationship to current or past ERT use was found. Duration of estrogen use was not associated with any atrophy measure. Cortical atrophy measure, sulcal widening, or white matter disease did not differ significantly by ERT use or duration of use. Central measures of atrophy, bifrontal distance, and ventricular size were significantly associated with cognition as measured by MMSE.

CONCLUSIONS

Current ERT users had much more clinically significant central atrophy than nonusers, but the implications remained unclear.

Measurement of global brain atrophy in Alzheimer's disease with unsupervised segmentation of spin-echo MRI studies

In 16 patients with probable Alzheimer's disease (AD; NINDS criteria, age range 56-78 years), gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) absolute and fractional volumes were measured with an unsupervised multiparametric post-processing segmentation method based on estimates of relaxation rates R1, R2 (R1 = 1/T1; R2 = 1/T2) and proton density [N(H)] from conventional spin-echo studies (Alfano et al. Magn. Reson. Med. 1997;37:84-93). Global brain atrophy, and GM and WM fractions significantly correlated with Mini-Mental Status Examination and Blessed Dementia Scale scores. Compared with normals, brain compartments in AD patients showed decreased GM (-6.84 +/- 1.58%) and WM fractions (-9.79 +/- 2.47%) and increased CSF fractions (+58.80 +/- 10.37%). Changes were more evident in early-onset AD patients. In AD, measurement of global brain atrophy obtained by a computerized procedure based on routine magnetic resonance studies could complement the information provided by neuropsychological tests for the assessment of disease severity.

Age-related brain changes associated with motor function in healthy older people

OBJECTIVE

To identify the MRI imaging findings associated with motor changes in healthy older people.

DESIGN

A cross-sectional study.

SETTING

A study of neurologic function in very healthy older people, the Oregon Brain Aging Study.

PARTICIPANTS

Clinical and MRI data were examined in 50 very healthy older subjects (mean age = 85.1, SD = 7.2 years).

MEASUREMENTS

Clinical measures (finger tapping, hand opening and closing, steps and time to walk 30 feet and timed standing on one foot) were dependent variables in multiple regression analyses using age and the following MRI measures as independent variables: total brain volume (TBV)/intracranial volume; ventricular volume/TBV; periventricular high signal/TBV; deep high signal/TBV.

RESULTS

The number of steps and the time to walk 30 feet were each associated with periventricular high signal (steps: r = .58, P < .001; time: r = .60, P < .001) and ventricular volume (steps: r = .54, P < .001; time: r = .58, P < .001). These associations remained significant after adjusting for age. None of the other clinical variables was associated with the MRI volumes.

CONCLUSIONS

Gait measures were associated significantly with periventricular high signal and ventricular volume. These CNS changes contribute to the cause of these important markers of aging.

Relationships of cerebral MRI findings to ultrasonographic carotid atherosclerosis in older adults : the Cardiovascular Health Study. CHS Collaborative Research Group

Cerebral magnetic resonance imaging (MRI) has demonstrated a high prevalence of infarct-like lesions, white matter hyperintensities, and evidence of cerebral atrophy in older adults. While these findings are generally believed to be related to ischemia and atherosclerosis, their relationship to atherosclerosis in the carotid arteries remains to be explored. Study subjects were part of the multicenter Cardiovascular Health Study, a cross-sectional study of 3502 women and men >/=65 years of age undergoing cranial MRI and carotid ultrasonography. MRI infarcts were detected in 1068 participants (29.3%) and measurable carotid plaque in 2745 (75.3%). MRI infarcts, ventricular and sulcal widening, and white matter score were strongly associated with carotid intimal-medial thickness (IMT) and stenosis degree after adjustment for age and sex (all P<0. 01). Associations with plaque characteristics were less strong and less consistent; MRI infarcts were weakly associated only with surface irregularity, and ventricular size was weakly associated only with lesion density (both P<0.04). In contrast, sulcal widening was strongly related to plaque characteristics, with scores being higher in those with heterogeneous and irregular plaque (both P<0. 009). Adjustment for other risk factors, and for carotid IMT/stenosis, removed associations of MRI findings with plaque characteristics except for weak relationships remaining between MRI infarcts and surface irregularity and between sulcal score and heterogeneous plaque (both P<0.03). MRI abnormalities show strong and consistent relationships with increasing carotid IMT and stenosis degree but less strong associations with plaque characteristics, especially after adjusting for IMT and stenosis.

Alzheimer's disease: the size of the problem, clinical manifestation and heterogeneity

Age is the major demographic risk factor for the development of Alzheimer's disease (AD) and the ageing of our society has contributed to the growing importance of AD. The problem of AD has been tackled from numerous clinical and scientific angles. The traditional clinico-pathological disease concept, which relies on the manifestation of a dementia syndrome and the elimination of other relevant systemic and brain diseases for a diagnosis of AD, accommodates a number of genetically and clinically heterogeneous conditions, but cannot promote our understanding of the preclinical pathogenetic processes and their interaction. If new molecular biological discoveries cannot be integrated with this traditional clinico-pathological model, it may have outlived its usefulness.

Glial reaction in aging and Alzheimer's disease

It is well-established that glial cells play an important role during injury and neurodegenerative processes in the central nervous system. In normal aging, no global glia proliferation is found morphologically, but reactive gliosis has been described in specific areas of the limbic system and neocortex that undergo selective neuronal or synaptic degeneration in nondemented elderly persons. In addition, there is an age-associated increase in the metabolic turnover of cellular proteins, such as glial fibrillary acidic protein, in human brain tissue, even without detectable signs of neurodegeneration. In contrast to the relatively moderate overall glial changes in normal aging, the close association of activated astrocytes and microglial cells with neuritic plaques and cells undergoing neurofibrillary degeneration in Alzheimer's disease (AD), the expression of receptors for complement by glial cells, and the release of soluble cytokines strongly suggest that inflammatory processes may play an important part in the complex pathophysiological interactions that occur in AD. Understanding the role of glia in age-associated neurodegenerative disorders may provide new insights into the neurobiology of glia-neuronal interaction and may allow the development of strategies to alter the disease process. This review aims to summarize some of the important aspects of glial cells in aging and dementia.

Relationship of senescence of cerebrospinal fluid circulatory system to dementias of the aged

In common with other organ systems, the cerebrospinal fluid circulatory system is subject to senescence. Cerebrospinal fluid production and turnover rates decline. The choroid plexus calcifies and its blood supply falters. Microvascular disease violates the integrity of the blood-brain barrier. The arachnoid membranes thicken. Arachnoid villi occlude and degenerate. The consequent functional losses are exacerbated by the deterioration of other interacting organ systems. Eventually, the cerebrospinal fluid circulatory system may fail, resulting in stagnation, contamination, compositional deficiencies, and impaired clearance of noxious substances. The hypothesis is that senescence of the cerebrospinal fluid circulatory system plays a part in some dementias of the aged.

Longitudinal cognitive, electroencephalographic and morphological brain changes in ageing and Alzheimer's disease

BACKGROUND

The natural course of cognitive performance, electrophysiological alterations and brain atrophy in ageing and Alzheimer's disease (AD) has been investigated in numerous studies, but only few attempts have been made to examine the relationship between clinical, electroencephalographic (EEG) and morphological changes with quantitative methods prospectively over longer periods of time.

METHOD

Fifty-five patients with clinically diagnosed AD and 66 healthy elderly controls were examined biannually using a cognitive test (CAMCOG), EEG band power and volumetric estimates of brain atrophy.

RESULTS

On average cognitive performance deteriorated by 28 points on the CAMCOG in the AD group, the alpha/theta ratio decreased by 0.2, and the proportion of intracranial cerebrospinal fluid volume increased by 3.5% during a 2-year period. Similar changes were observed after a second 2-year interval. A multiple regression model demonstrated a significant influence of age on cognition and atrophy and a significant influence of the estimated duration of symptoms on cognition, alpha/theta ratio and brain atrophy at the initial examination. Cognitive performance at the first examination exerted significant effects on the performance and also on brain atrophy at re-examination after 2 or 4 years, whereas the EEG and neuroimaging findings at the previous examination were exclusively related to the corresponding findings at the follow-up examinations. In the control group no significant cognitive, EEG and morphological changes were observed after 2 and 4 years.

CONCLUSION

After 2 consecutive follow-up periods, we were able to verify significant deteriorations of cognition accompanied by neurophysiological and neuroradiological changes in AD, but not in normal ageing. In clinically diagnosed AD, cognitive performance at the followup examination could not be predicted by the previous alpha/theta ratio or by the previous degree of global brain atrophy, whereas the cognitive test score determined not only performance, but also structural findings at follow-up. Performance on cognitive tests appears to be a more sensitive indicator of the degenerative process than EEG band-power and morphological changes in manifest AD. Neuroimaging, neurophysiology and genetic risk markers may be more important for the early differential diagnosis than for the prediction of the course of illness.