Samuel Groeschel

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INTRODUCTION Virchow-Robin spaces (VRS) are perivascular spaces in the brain and can be visualized on magnetic resonance images (MRI). We attempt to provide a better understanding of the significance of VRS for pathological and physiological processes by reviewing the literature, presenting normative data for the first time, and proposing a definition for(More)
There has been extensive interest in assessing the long-term effects of preterm birth on brain white matter microstructure using diffusion MRI. Our aim in this study is to explore diffusion MRI differences between adolescents born preterm and term born controls, with a specific interest in characterising how such differences are manifested in white matter(More)
BACKGROUND Metachromatic leukodystrophy (MLD) is a rare, genetic neurodegenerative disease. It leads to progressive demyelination resulting in regression of development and early death. With regard to experimental therapies, knowledge of the natural course of the disease is highly important. We aimed to analyse onset and character of first symptoms in MLD(More)
In this study, we analyzed the structural connectivity of cortico-cortical and cortico-subcortical language networks in healthy children, using probabilistic tractography based on high angular resolution diffusion imaging. In addition to anatomically defining seed and target regions for tractography, we used fMRI to target inferior frontal and superior(More)
Megalencephaly with dilated Virchow-Robin spaces has been suggested to represent a new clinical entity. This report describes two males and a female who have been monitored from pregnancy. The patients manifest a relatively normal psychomotor development with some minor neurologic symptoms such as mild muscle hypotonia and clumsy motor performance.(More)
OBJECTIVE Metachromatic leukodystrophy (MLD) is a rare metabolic disorder leading to demyelination and rapid neurologic deterioration. As therapeutic options evolve, it seems essential to understand and quantify progression of the natural disease. The aim of this study was to assess cerebral volumetric changes in children with MLD in comparison to normal(More)
Spherical deconvolution models the diffusion MRI signal as the convolution of a fiber orientation density function (fODF) with a single fiber response. We propose a novel calibration procedure that automatically determines this fiber response. This has three advantages: First, the user no longer needs to provide an estimate of the response. Second, we(More)
Resting-state functional magnetic resonance imaging (fMRI) can be used to study the functional connectivity in the somatosensory system. However, the relationship between sensory network connectivity, sensory deficits, and structural abnormality remains poorly understood. Previously, we investigated the motor network in children with congenital hemiparesis(More)
RATIONALE AND OBJECTIVES Metachromatic leukodystrophy is a lysosomal storage disorder leading to progressive demyelination of brain white matter. This is sensitively detected using magnetic resonance imaging. The volume of demyelination, the "demyelination load," could serve as a useful parameter for assessing both the natural course of the disease and(More)
We propose a new regularization for spherical deconvolution in diffusion MRI. It is based on observing that higher-order tensor representations of fiber ODFs should be H-psd, i.e., they should have a positive semidefinite (psd) matrix HT. We show that this constraint is stricter than the currently more widely used non-negativity, and that it can be enforced(More)