Temporal changes in brain volume and cognition in a randomized treatment trial of vascular dementia

Subcortical atrophy in frontotemporal dementia and Alzheimer's disease: Significance for the differential diagnosis and correlations with clinical manifestations

Cerebral subcortical atrophy occurs in both Alzheimer’s disease (AD) and frontotemporal dementia (FTD) but its significance for clinical manifestations and differential diagnosis between these common types of dementia has not been extensively investigated.

Evaluation of treatment effects in Alzheimer's and other neurodegenerative diseases by MRI and MRS

Neurodegeneration refers to a large clinically and pathologically heterogeneous disease entity associated with slowly progressive neuronal loss in different anatomical and functional systems of the brain. Neurodegenerative diseases often affect cognition, e.g. Alzheimer's disease (AD), dementia with Lewy bodies and vascular dementia, or different aspects of the motor system, e.g., amyotrophic lateral sclerosis, Parkinson's disease and ataxic disorders. Owing to increasing knowledge about the mechanisms leading to neurodegeneration, the development of treatments able to modify the neurodegenerative process becomes possible for the first time. Currently, clinical outcome measures are used to assess the efficacy of such treatments. However, most clinical outcome measures have a low test-retest reliability and thus considerable measurement variance. Therefore, large patient populations and long observation times are needed to detect treatment effects. Furthermore, clinical outcome measures cannot distinguish between symptomatic and disease-modifying treatment effects. Therefore, alternative biomarkers including neuroimaging may take on a more important role in this process. Because MR scanners are widely available and allow for non-invasive detection and quantification of changes in brain structure and metabolism, there is increasing interest in the use of MRI/MRS to monitor objectively treatment effects in clinical trials of neurodegenerative diseases. Particularly volumetric MRI has been used to measure atrophy rates in treatment trials of AD because the relationship between atrophic changes and neuron loss is well established and correlates well with clinical measures. More research is needed to determine the value of other MR modalities, i.e. diffusion, perfusion and functional MRI and MR spectroscopy, for clinical trials with neuroprotective drugs.

Neuroimaging and cardiac correlates of cognitive function among patients with cardiac disease

In the present study, we examined the relationships between whole brain volume (WBV), subcortical hyperintensities (SH), indices of cardiac disease and cognitive function in nondemented cardiac patients with evidence of mild cerebrovascular disease. A total of 27 individuals with evidence of cardiac disease underwent neuropsychological examination, neuroimaging, and cardiac assessment. Cognition was assessed with the Dementia Rating Scale-2 (DRS). WBV and SH were quantified using a semi-automated thresholding program based on MRI. Correlational analyses revealed that WBV predicted performance on the overall DRS score, the attention subscale and the initiation/perseveration scale. SH were significantly associated with performance on the attention subscale, and the initiation/perseveration subscale. Regression analyses revealed that SH accounted for most of the variance in the initiation/perseveration scale, whereas WBV accounted for most of the variance in the attention scale. The only cardiac structural or functional variable related to the neurological indices was aortic diameter, which was strongly related to both neuroimaging variables, as well as performances on the DRS attention and initiation/perseveration subscales. Our results highlight the importance of overall brain parenchyma in determining cognitive status among patients at risk for cognitive decline and suggest that select indices of structural cardiac morphology may be related to the early phases of cerebrovascular disease and cognitive status.

Neuroimaging correlates of dementia rating scale performance at baseline and 12-month follow-up among patients with vascular dementia

The authors previously reported that subcortical hyperintensity (SH) and whole-brain volume (WBV) each covary with different subscale scores of the Mattis Dementia Rating Scale (MDRS) among vascular dementia (VaD) patients. The present longitudinal analysis examined these relationships for change. The authors found that SH volume increased and WBV decreased significantly over 12 months. At baseline, SH volume accounted for significant variance in MDRS total score and every subscale score, except Memory. WBV was unrelated to any MDRS measure. After 12 months, SH volume was related only to the Construction subscale score, whereas WBV accounted for the majority of variance in Attention and Memory subscale performance. These findings indicate that although SH volume increases with disease progression, the relative impact of SH volume on cognitive status decreases among patients with advanced VaD.

Quantitative image analysis: software systems in drug development trials

Multi-dimensional image analysis is being used increasingly to arrive at surrogate end-points for drug development trials. Various imaging modalities such as computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET) and ultrasound are used to analyze treatments for diseases such as cancer, multiple sclerosis, osteoarthritis, and Alzheimer's disease. However, extracting information from images can be tedious and is prone to high user variability. The medical image analysis community is moving towards advanced software systems specifically designed for drug development trials. These systems can automatically identify the anatomy of interest in medical images (segmentation methods), can compare the anatomy over time or between patients (registration methods) and allow the quantitative extraction of anatomical features and the integration of the data and results into a database management system, automatically tracking the changes made to the data (audit trail generation). In this article, we present a case study using a prototype system that is used for quantifying multiple sclerosis lesions from multivariate MRI.

Transient ischaemic attacks are associated with increased rates of global cerebral atrophy

OBJECTIVES

To determine whether patients presenting with a first transient ischaemic attack (TIA) subsequently show increased rates of brain atrophy compared with age matched controls; and to assess potential risk factors for brain atrophy in this group.

METHODS

60 patients with a first, isolated TIA and 26 age and sex matched controls were recruited. None had evidence of cognitive impairment. Vascular risk factors were treated appropriately. All subjects had volumetric imaging at the start of the study and one year later, when they were clinically reassessed. TIA patients also had serial dual echo brain imaging. Rates of whole brain atrophy were calculated from the registered volumetric scans, as was the incidence of new ischaemic lesions. In the TIA group, the degree of white matter disease was assessed. Atrophy rates and blood pressure were compared between patients and controls.

RESULTS

22 patients (37%) developed new "clinically silent" infarcts during follow up. The mean (SD) annualised percentage atrophy rate in the TIA group was significantly higher than in the controls, at 0.82 (0.39)% v 0.33 (0.3)% (p < 0.0001). In the TIA group, diastolic blood pressure (p = 0.004) and white matter disease severity (p < 0.001) were correlated with cerebral atrophy rate. Increased white matter disease was found in patients in whom new ischaemic lesions developed (p < 0.001).

CONCLUSIONS

Patients presenting with a first TIA have excess global brain atrophy compared with age matched controls over the subsequent year. Increased atrophy rates following a TIA may be directly or indirectly related to increasing white matter disease and diastolic hypertension. Future studies should assess whether this atrophy inevitably leads to cognitive decline, and whether aggressive treatment of risk factors for cerebrovascular disease (particularly hypertension) after a TIA can influence outcome.