Alzheimer Disease: Karas G

Burton EJ, Karas G, Paling SM, Barber R, Williams ED, Ballard CG, McKeith IG, Scheltens P, Barkhof F, O'Brien JT. · Institute for Ageing and Health, University of Newcastle upon Tyne, United Kingdom. · Neuroimage. · Pubmed #12377138 No free full text.

Abstract: Previous cross-sectional MRI studies based on region-of-interest analyses have shown that increased cerebral atrophy is a feature of both Dementia with Lewy bodies (DLB) and Alzheimer's disease (AD). Relative preservation of the hippocampus and temporal lobe structures in DLB compared to AD has been reported in region-of-interest-based studies. Recently, image processing techniques such as voxel-based morphometry (VBM) have been developed to provide an unbiased, visually informative, and comprehensive means of studying patterns of cerebral atrophy. We report the first study to use the voxel-based approach to assess patterns of cerebral atrophy in DLB compared to control subjects and AD. Regional gray matter volume loss was observed bilaterally in the temporal and frontal lobes and insular cortex of patients with DLB compared to control subjects. Comparison of dementia groups showed preservation of the medial temporal lobe, hippocampus, and amygdala in DLB relative to AD. Significant gray matter loss was also observed in the thalamus of AD patients compared to DLB.

Karas G, Sluimer J, Goekoop R, van der Flier W, Rombouts SA, Vrenken H, Scheltens P, Fox N, Barkhof F. · Department of Diagnostic Radiology, VU University Medical Center, Amsterdam, the Netherlands. · AJNR Am J Neuroradiol. · Pubmed #18296551 links to  free full text

Abstract: BACKGROUND AND PURPOSE: Mild cognitive impairment (MCI) is considered by many to be a prodromal phase of Alzheimer disease (AD). We used voxel-based morphometry (VBM) to find out whether structural differences on MR imaging could offer insight into the development of clinical AD in patients with amnestic MCI at 3-year follow-up. MATERIALS AND METHODS: Twenty-four amnestic patients with MCI were included. After 3 years, 46% had progressed to AD (n = 11; age, 72.7 +/- 4.8 years; women/men, 8/3). For 13 patients (age, 72.4 +/- 8.6 years; women/men, 10/3), the diagnosis remained MCI. Baseline MR imaging at 1.5T included a coronal heavily T1-weighted 3D gradient-echo sequence. Localized gray matter differences were assessed with VBM. RESULTS: The converters had less gray matter volume in medial (including the hippocampus) and lateral temporal lobe, parietal lobe, and lateral temporal lobe structures. After correction for age, sex, total gray matter volume, and neuropsychological evaluation, left-sided atrophy remained statistically significant. Specifically, converters had more left parietal atrophy (angular gyrus and inferior parietal lobule) and left lateral temporal lobe atrophy (superior and middle temporal gyrus) than stable patients with MCI. CONCLUSION: By studying 2 MCI populations, converters versus nonconverters, we found atrophy beyond the medial temporal lobe to be characteristic of patients with MCI who will progress to dementia. Atrophy of structures such as the left lateral temporal lobe and left parietal cortex may independently predict conversion.

Karas G, Scheltens P, Rombouts S, van Schijndel R, Klein M, Jones B, van der Flier W, Vrenken H, Barkhof F. · Department of Diagnostic Radiology, Vrije Universiteit Medical Centre, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands. · Neuroradiology. · Pubmed #17955233 No free full text.

Abstract: INTRODUCTION: Alzheimer's disease (AD) usually first presents in elderly patients, but may also develop at an earlier age. Patients with an early age at onset tend to present with complaints other than memory impairment, such as visuospatial problems or apraxia, which may reflect a different distribution of cortical involvement. In this study we set out to investigate whether age at onset in patients with AD determines the pattern of atrophy on cerebral MRI scans. METHODS: We examined 55 patients with AD over a wide age range and analyzed their 3-D T1-weighted structural MRI scans in standard space using voxel-based morphometry (VBM). Regression analysis was performed to estimate loss of grey matter as a function of age, corrected for mini-mental state examination (MMSE) scores and sex. RESULTS: The VBM analyses identified multiple areas (including the temporal and parietal lobes), showing more atrophy with advancing age. By contrast, a younger age at onset was found to be associated with lower grey matter density in the precuneus. Regionalized volumetric analysis of this region confirmed the existence of disproportionate atrophy in the precuneus in patients with early-onset AD. Application of a multivariate model with precuneus grey matter density as input, showed that precuneal and hippocampal atrophy are independent from each other. Additionally, we found that a smaller precuneus is associated with impaired visuospatial functioning. CONCLUSION: Our findings support the notion that age at onset modulates the distribution of cortical involvement, and that disproportionate precuneus atrophy is more prominent in patients with a younger age of onset.

van Straaten EC, Scheltens P, Knol DL, van Buchem MA, van Dijk EJ, Hofman PA, Karas G, Kjartansson O, de Leeuw FE, Prins ND, Schmidt R, Visser MC, Weinstein HC, Barkhof F. · Department of Neurology and Alzheimer Center, VU Medical Center, De Boelelaan 1117, PO Box 7057, 1007 MB Amsterdam, Netherlands. · Stroke. · Pubmed #12855825 links to  free full text

Abstract: BACKGROUND AND PURPOSE: Vascular dementia (VaD) is thought to be the most common cause of dementia after Alzheimer's disease. The commonly used International Workshop of the National Institute of Neurological Disorders and Stroke (NINDS) and the Association Internationale pour la Recherche et l'Enseignement en Neurosciences (AIREN) criteria for VaD necessitate evidence of vascular disease on CT or MRI of the brain. The purposes of our study were to operationalize the radiological part of the NINDS-AIREN criteria and to assess the effect of this operationalization on interobserver agreement. METHODS: Six experienced and 4 inexperienced observers rated a set of 40 MRI studies of patients with clinically suspected VaD twice using the NINDS-AIREN set of radiological criteria. After the first reading session, operational definitions were conceived, which were subsequently used in the second reading session. Interobserver reproducibility was measured by Cohen's kappa. RESULTS: Overall agreement at the first reading session was poor (kappa=0.29) and improved slightly after application of the additional definitions (kappa=0.38). Raters in the experienced group improved their agreement from almost moderate (kappa=0.39) to good (0.62). The inexperienced group started out with poor agreement (kappa=0.17) and did not improve (kappa=0.18). The experienced group improved in both the large- and small-vessel categories, whereas the inexperienced group improved generally in the extensive white matter hyperintensities categories. CONCLUSIONS: Considerable interobserver variability exists for the assessment of the radiological part of the NINDS-AIREN criteria. Use of operational definitions improves agreement but only for already experienced observers.