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Sökning: WFRF:(Ropele Stefan)

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  • Hibar, Derrek P., et al. (författare)
  • Novel genetic loci associated with hippocampal volume
  • 2017
  • Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 8
  • Tidskriftsartikel (refereegranskat)abstract
    • The hippocampal formation is a brain structure integrally involved in episodic memory, spatial navigation, cognition and stress responsiveness. Structural abnormalities in hippocampal volume and shape are found in several common neuropsychiatric disorders. To identify the genetic underpinnings of hippocampal structure here we perform a genome-wide association study (GWAS) of 33,536 individuals and discover six independent loci significantly associated with hippocampal volume, four of them novel. Of the novel loci, three lie within genes (ASTN2, DPP4 and MAST4) and one is found 200 kb upstream of SHH. A hippocampal subfield analysis shows that a locus within the MSRB3 gene shows evidence of a localized effect along the dentate gyrus, subiculum, CA1 and fissure. Further, we show that genetic variants associated with decreased hippocampal volume are also associated with increased risk for Alzheimer's disease (r(g) = -0.155). Our findings suggest novel biological pathways through which human genetic variation influences hippocampal volume and risk for neuropsychiatric illness.
  • Dyrby, Tim B, et al. (författare)
  • Segmentation of age-related white matter changes in a clinical multi-center study.
  • 2008
  • Ingår i: NeuroImage. - 1053-8119. ; 41:2, s. 335-45
  • Tidskriftsartikel (refereegranskat)abstract
    • Age-related white matter changes (WMC) are thought to be a marker of vascular pathology, and have been associated with motor and cognitive deficits. In the present study, an optimized artificial neural network was used as an automatic segmentation method to produce probabilistic maps of WMC in a clinical multi-center study. The neural network uses information from T1- and T2-weighted and fluid attenuation inversion recovery (FLAIR) magnetic resonance (MR) scans, neighboring voxels and spatial location. Generalizability of the neural network was optimized by including the Optimal Brain Damage (OBD) pruning method in the training stage. Six optimized neural networks were produced to investigate the impact of different input information on WMC segmentation. The automatic segmentation method was applied to MR scans of 362 non-demented elderly subjects from 11 centers in the European multi-center study Leukoaraiosis And Disability (LADIS). Semi-manually delineated WMC were used for validating the segmentation produced by the neural networks. The neural network segmentation demonstrated high consistency between subjects and centers, making it a promising technique for large studies. For WMC volumes less than 10 ml, an increasing discrepancy between semi-manual and neural network segmentation was observed using the similarity index (SI) measure. The use of all three image modalities significantly improved cross-center generalizability compared to neural networks using the FLAIR image only. Expert knowledge not available to the neural networks was a minor source of discrepancy, while variation in MR scan quality constituted the largest source of error.
  • Fazekas, F., et al. (författare)
  • Brain Magnetic Resonance Imaging Findings Fail to Suspect Fabry Disease in Young Patients With an Acute Cerebrovascular Event
  • 2015
  • Ingår i: Stroke. - : American Heart Association. - 0039-2499. ; 46:6, s. 1548-1548
  • Tidskriftsartikel (refereegranskat)abstract
    • Background and Purpose-Fabry disease (FD) may cause stroke and is reportedly associated with typical brain findings on magnetic resonance imaging (MRI). In a large group of young patients with an acute cerebrovascular event, we wanted to test whether brain MRI findings can serve to suggest the presence of FD. Methods-The Stroke in Young Fabry Patients (SIFAP 1) study prospectively collected clinical, laboratory, and radiological data of 5023 patients (18-55 years) with an acute cerebrovascular event. Their MRI was interpreted centrally and blinded to all other information. Biochemical findings and genetic testing served to diagnose FD in 45 (0.9%) patients. We compared the imaging findings between FD and non-FD patients in patients with at least a T2-weighted MRI of good quality. Results-A total of 3203 (63.8%) patients had the required MRI data set. Among those were 34 patients with a diagnosis of FD (1.1%), which was definite in 21 and probable in 13 cases. The median age of patients with FD was slightly lower (45 versus 46 years) and women prevailed (70.6% versus 40.7%; P<0.001). Presence or extent of white matter hyperintensities, infarct localization, vertebrobasilar artery dilatation, T1-signal hyperintensity of the pulvinar thalami, or any other MRI finding did not distinguish patients with FD from non-FD cerebrovascular event patients. Pulvinar hyperintensity was not present in a single patient with FD but seen in 6 non-FD patients. Conclusions-Brain MRI findings cannot serve to suspect FD in young patients presenting with an acute cerebrovascular event. This deserves consideration in the search for possible causes of young patients with stroke.
  • Ropele, Stefan, et al. (författare)
  • Quantitation of brain tissue changes associated with white matter hyperintensities by diffusion-weighted and magnetization transfer imaging: the LADIS (Leukoaraiosis and Disability in the Elderly) study.
  • 2009
  • Ingår i: Journal of magnetic resonance imaging : JMRI. - 1053-1807. ; 29:2, s. 268-74
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: To explore the value of diffusion-weighted imaging (DWI) and magnetization transfer imaging (MTI) for the improved detection and quantification of cerebral tissue changes associated with ageing and white matter hyperintensities (WMH). MATERIALS AND METHODS: DWI (n = 340) and MTI (n = 177) were performed in nine centers of the multinational Leukoaraiosis And DISability (LADIS) study investigating the impact of WMH on 65- to 85-year-old individuals without prior disability. We assessed the apparent diffusion coefficient (ADC) and magnetization transfer ratio (MTR) of normal appearing brain tissue (NABT) and within WMH and related them to subjects' age and WHM severity according to the Fazekas score. RESULTS: ADC and MTR values showed a significant inter-site variation, which was stronger for the MTR. After z-transformation multiple regression analysis revealed WMH severity and age as significant predictors of global ADC and MTR changes. Only lesional ADC, but not MTR was related to WMH severity. CONCLUSION: ADC and MTR are both sensitive for age and WMH related changes in NABT. The ADC is more sensitive for tissue changes within WMH and appears to be more robust for multicenter settings.
  • De Guio, François, et al. (författare)
  • Reproducibility and variability of quantitative magnetic resonance imaging markers in cerebral small vessel disease
  • 2016
  • Ingår i: Journal of Cerebral Blood Flow and Metabolism. - : Nature Publishing Group. - 0271-678X. ; 36:8, s. 1319-1337
  • Forskningsöversikt (refereegranskat)abstract
    • Brain imaging is essential for the diagnosis and characterization of cerebral small vessel disease. Several magnetic resonance imaging markers have therefore emerged, providing new information on the diagnosis, progression, and mechanisms of small vessel disease. Yet, the reproducibility of these small vessel disease markers has received little attention despite being widely used in cross-sectional and longitudinal studies. This review focuses on the main small vessel disease-related markers on magnetic resonance imaging including: white matter hyperintensities, lacunes, dilated perivascular spaces, microbleeds, and brain volume. The aim is to summarize, for each marker, what is currently known about: (1) its reproducibility in studies with a scan-rescan procedure either in single or multicenter settings; (2) the acquisition-related sources of variability; and, (3) the techniques used to minimize this variability. Based on the results, we discuss technical and other challenges that need to be overcome in order for these markers to be reliably used as outcome measures in future clinical trials. We also highlight the key points that need to be considered when designing multicenter magnetic resonance imaging studies of small vessel disease.
  • Ikram, M. Arfan, et al. (författare)
  • Common variants at 6q22 and 17q21 are associated with intracranial volume
  • 2012
  • Ingår i: Nature Genetics. - 1061-4036 .- 1546-1718. ; 44:5, s. 539-544
  • Tidskriftsartikel (refereegranskat)abstract
    • During aging, intracranial volume remains unchanged and represents maximally attained brain size, while various interacting biological phenomena lead to brain volume loss. Consequently, intracranial volume and brain volume in late life reflect different genetic influences. Our genome-wide association study (GWAS) in 8,175 community-dwelling elderly persons did not reveal any associations at genome-wide significance (P < 5 x 10(-8)) for brain volume. In contrast, intracranial volume was significantly associated with two loci: rs4273712 (P = 3.4 x 10(-11)), a known height-associated locus on chromosome 6q22, and rs9915547 (P = 1.5 x 10(-12)), localized to the inversion on chromosome 17q21. We replicated the associations of these loci with intracranial volume in a separate sample of 1,752 elderly persons (P = 1.1 x 10(-3) for 6q22 and 1.2 x 10(-3) for 17q21). Furthermore, we also found suggestive associations of the 17q21 locus with head circumference in 10,768 children (mean age of 14.5 months). Our data identify two loci associated with head size, with the inversion at 17q21 also likely to be involved in attaining maximal brain size.
  • Rolfs, Arndt, et al. (författare)
  • Protocol and Methodology of the Stroke in Young Fabry Patients (sifap1) Study: A Prospective Multicenter European Study of 5,024 Young Stroke Patients Aged 18-55 Years
  • 2011
  • Ingår i: Cerebrovascular Diseases. - : Karger. - 1421-9786. ; 31:3, s. 253-262
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Stroke in the young has not been thoroughly investigated with most previous studies based on a small number of patients from single centers. Furthermore, recent reports indicate that Fabry disease may be a significant cause for young stroke. The primary aim of our study was to determine the prevalence of Fabry disease in young stroke patients, while the secondary aim was to describe patterns of stroke in young patients. Methods: We initiated the Stroke in Young Fabry Patients (sifap1) study as a multinational prospective European study of stroke patients aged 18-55 years and collected a broad range of clinical, laboratory, and radiological data using stringent standardized methods. All patients were tested for Fabry disease and blood was stored for future genetic testing. Results: We managed to enroll 5,024 eligible young stroke patients in 15 countries and 47 centers across Europe between April 2007 and January 2010. The median number of patients included per center was 98 with a range between 8 and 315. The average duration of patient recruitment per center was 22 months, ranging between 5 and 33 months. The database was closed in July 2010. This paper describes protocol and methodology of the sifap1 study. Conclusion: The sifap1 study included the largest series of young stroke patients so far and will allow for analyses on a large number of aspects of stroke in the young. Copyright (C) 2010 S. Karger AG, Basel
  • Taal, H. Rob, et al. (författare)
  • Common variants at 12q15 and 12q24 are associated with infant head circumference
  • 2012
  • Ingår i: Nature Genetics. - 1061-4036 .- 1546-1718. ; 44:5, s. 532-538
  • Tidskriftsartikel (refereegranskat)abstract
    • To identify genetic variants associated with head circumference in infancy, we performed a meta-analysis of seven genome-wide association studies (GWAS) (N = 10,768 individuals of European ancestry enrolled in pregnancy and/or birth cohorts) and followed up three lead signals in six replication studies (combined N = 19,089). rs7980687 on chromosome 12q24 (P = 8.1 x 10(-9)) and rs1042725 on chromosome 12q15 (P = 2.8 x 10(-10)) were robustly associated with head circumference in infancy. Although these loci have previously been associated with adult height(1), their effects on infant head circumference were largely independent of height (P = 3.8 x 10(-7) for rs7980687 and P = 1.3 x 10(-7) for rs1042725 after adjustment for infant height). A third signal, rs11655470 on chromosome 17q21, showed suggestive evidence of association with head circumference (P = 3.9 x 10(-6)). SNPs correlated to the 17q21 signal have shown genome-wide association with adult intracranial volume(2), Parkinson's disease and other neurodegenerative diseases(3-5), indicating that a common genetic variant in this region might link early brain growth with neurological disease in later life.
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