Publications by authors named "Romain Valabregue"

Cerebellar functional and structural connectivity are likely related to motor function after stroke. Less is known about motor recovery, which is defined as a gain of function between two time points, and about the involvement of the cerebellum. Fifteen patients who were hospitalized between 2018 and 2020 for a first cerebral ischemic event with persistent upper limb deficits were assessed by resting-state functional MRI (rsfMRI) and clinical motor score measurements at 3, 9 and 15 weeks after stroke.

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Segmentation is a critical step in analyzing the developing human fetal brain. There have been vast improvements in automatic segmentation methods in the past several years, and the Fetal Brain Tissue Annotation (FeTA) Challenge 2021 helped to establish an excellent standard of fetal brain segmentation. However, FeTA 2021 was a single center study, limiting real-world clinical applicability and acceptance.

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  • The study explores myoclonus dystonia caused by a variant in the SGCE gene, focusing on the microarchitectural brain abnormalities linked to this rare condition.
  • Researchers compared the brain structures of 18 MYC/DYT-SGCE patients with 24 healthy volunteers using advanced imaging techniques to assess neurite organization.
  • Results indicate that patients exhibited changes in cerebellar structure, with specific alterations correlating to the severity of dystonia, while no links were found between myoclonus severity and the microarchitectural measurements.
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  • The study investigates the relationship between the structure and function of the corticospinal tract (CST) in predicting motor recovery after a stroke, focusing on patients within a week of experiencing an acute ischemic stroke.
  • Involving 70 patients with unilateral upper extremity weakness, it utilized clinical assessment, MRI scans to check CST lesion load, and transcranial magnetic stimulation to gauge motor functions.
  • Results show that a high CST lesion load can accurately predict a lack of motor response, and the relationship between CST structure and function varies based on the amplitude of the motor evoked potentials (MEP), influencing recovery patterns in stroke patients.
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Background: Early prediction of poststroke motor recovery is challenging in clinical settings. The Prediction recovery potential (PREP2) algorithm is the most accurate approach for prediction of Upper Limb function available to date but lacks external validation.

Objectives: (i) To externally validate the PREP2 algorithm in a prospective cohort, (ii) to study the characteristics of patients misclassified by the algorithm, and (iii) to compare the performance according to the presence of cognitive syndromes (aphasia, neglect, cognitive disorders).

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  • Clinical trials for spinocerebellar ataxias (SCA) need better endpoints to measure early disease progression and effectiveness of treatments, as current measures focus on later stages.
  • The READISCA consortium found that advanced multimodal magnetic resonance imaging (MRI) can track changes in brain structure and function over 6 months in participants with early-stage SCA mutations, indicating disease progression.
  • Results showed significant differences in microstructural changes between SCA patients and controls, suggesting that diffusion MRI could reduce the sample size needed for future trials compared to traditional assessments like the Scale for Assessment and Rating of Ataxia (SARA).
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  • Deep learning is used for medical image segmentation, but it struggles with small training datasets and can produce inaccurate results; anatomical knowledge can help improve this process.
  • A new loss function based on projected pooling introduces soft topological constraints by highlighting smaller parts of the structure to ensure they aren't overlooked during segmentation.
  • When applied to segment the red nucleus in QSM data, this method achieved high accuracy (Dice 89.9%) and minimized topological errors, making it a promising approach for efficient and accurate medical image segmentation.
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Background: The locus coeruleus (LC) and the nucleus basalis of Meynert (NBM) are altered in early stages of Alzheimer's disease (AD). Little is known about LC and NBM alteration in limbic-predominant age-related TDP-43 encephalopathy (LATE) and frontotemporal dementia (FTD). The aim of the present study is to investigate in vivo LC and NBM integrity in patients with suspected-LATE, early-amnestic AD and FTD in comparison with controls.

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  • This study investigates the non-motor aspects of myoclonus dystonia, focusing on the sense of agency, which is how individuals perceive control over their actions, and how disruptions in this sense can affect movement disorders.* -
  • The research compared 19 patients with myoclonus dystonia (stemming from a specific genetic variant) to 24 healthy participants, revealing that the patients had a significant impairment in their explicit sense of agency, while their implicit sense remained unaffected.* -
  • Neuroimaging analyses showed structural and functional abnormalities in the cerebellum and its connectivity with the pre-supplementary motor area, suggesting these brain regions play a crucial role in the altered sense of agency in patients with my
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Introduction: Parieto-frontal interactions are mediated by the superior longitudinal fasciculus (SLF) and are crucial to integrate visuomotor information and mediate fine motor control. In this study, we aimed to characterize the relation of white matter integrity of both parts of the SLF (SLF I and SLF II) to both motor outcome and recovery and its evolution over time in stroke patients with upper limb motor deficits.

Materials And Methods: Fractional anisotropy (FA) values over the SLF I, SLF II, and corticospinal tract (CST) and upper limb motor performance evaluated by both the upper limb Fugl-Meyer Assessment score and maximum grip strength were measured for 16 patients at 3 weeks, 6 weeks, and 12 weeks poststroke.

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Background: Cervical dystonia (CD) is a form of isolated focal dystonia typically associated to abnormal head, neck, and shoulder movements and postures. The complexity of the clinical presentation limits the investigation of its pathophysiological mechanisms, and the neural networks associated to specific motor manifestations are still the object of debate.

Objectives: We investigated the morphometric properties of white matter fibers in CD and explored the networks associated with motor symptoms, while regressing out nonmotor scores.

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Introduction: The cerebellum and basal ganglia were initially considered anatomically distinct regions, each connected thalamic relays which project to the same cerebral cortical targets, such as the motor cortex. In the last two decades, transneuronal viral transport studies in non-human primates showed bidirectional connections between the cerebellum and basal ganglia at the subcortical level, without involving the cerebral cortical motor areas. These findings have significant implications for our understanding of neurodevelopmental and neurodegenerative diseases.

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Background: The locus coeruleus/subcoeruleus complex (LC/LsC) is a structure comprising melanized noradrenergic neurons.

Objective: To study the LC/LsC damage across Parkinson's disease (PD) and atypical parkinsonism in a large group of subjects.

Methods: We studied 98 healthy control subjects, 47 patients with isolated rapid eye movement sleep behavior disorder (RBD), 75 patients with PD plus RBD, 142 patients with PD without RBD, 19 patients with progressive supranuclear palsy (PSP), and 19 patients with multiple system atrophy (MSA).

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Objective: This study was undertaken to identify magnetic resonance (MR) metrics that are most sensitive to early changes in the brain in spinocerebellar ataxia type 1 (SCA1) and type 3 (SCA3) using an advanced multimodal MR imaging (MRI) protocol in the multisite trial setting.

Methods: SCA1 or SCA3 mutation carriers and controls (n = 107) underwent MR scanning in the US-European READISCA study to obtain structural, diffusion MRI, and MR spectroscopy data using an advanced protocol at 3T. Morphometric, microstructural, and neurochemical metrics were analyzed blinded to diagnosis and compared between preataxic SCA (n = 11 SCA1, n = 28 SCA3), ataxic SCA (n = 14 SCA1, n = 37 SCA3), and control (n = 17) groups using nonparametric testing accounting for multiple comparisons.

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Background: Parkinson's disease (PD) demonstrates neurodegenerative changes in the substantia nigra pars compacta (SNc) using neuromelanin-sensitive (NM)-MRI. As SNc manual segmentation is prone to substantial inter-individual variability across raters, development of a robust automatic segmentation framework is necessary to facilitate nigral neuromelanin quantification. Artificial intelligence (AI) is gaining traction in the neuroimaging community for automated brain region segmentation tasks using MRI.

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Background And Objectives: D-2-hydroxyglutarate (2HG) characterizes -mutant gliomas and can be detected and quantified with edited MRS (MEGA-PRESS). In this study, we investigated the clinical, radiologic, and molecular parameters affecting 2HG levels.

Methods: MEGA-PRESS data were acquired in 71 patients with glioma (24 untreated, 47 treated) on a 3 T system.

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Advances in deep learning can be applied to acute stroke imaging to build powerful and explainable prediction models that could supersede traditionally used biomarkers. We aimed to evaluate the performance and interpretability of a deep learning model based on convolutional neural networks (CNN) in predicting long-term functional outcome with diffusion-weighted imaging (DWI) acquired at day 1 post-stroke. Ischemic stroke patients (n = 322) were included from the ASTER and INSULINFARCT trials as well as the Pitié-Salpêtrière registry.

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Background: Neurodegeneration in the substantia nigra pars compacta (SNc) in parkinsonian syndromes may affect the nigral territories differently.

Objective: The objective of this study was to investigate the regional selectivity of neurodegenerative changes in the SNc in patients with Parkinson's disease (PD) and atypical parkinsonism using neuromelanin-sensitive magnetic resonance imaging (MRI).

Methods: A total of 22 healthy controls (HC), 38 patients with PD, 22 patients with progressive supranuclear palsy (PSP), 20 patients with multiple system atrophy (MSA, 13 with the parkinsonian variant, 7 with the cerebellar variant), 7 patients with dementia with Lewy body (DLB), and 4 patients with corticobasal syndrome were analyzed.

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Cerebellum is a key structure for functional motor recovery after stroke. Enhancing the cerebello-motor pathway by paired associative stimulation (PAS) might improve upper limb function. Here, we conducted a randomized, double-blind, sham-controlled pilot trial investigating the efficacy of a 5-day treatment of cerebello-motor PAS coupled with physiotherapy for promoting upper limb motor function compared to sham stimulation.

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Background: Isolated REM sleep behavior disorder (iRBD) is considered a prodromal stage of parkinsonism. Neurodegenerative changes in the substantia nigra pars compacta (SNc) in parkinsonism can be detected using neuromelanin-sensitive MRI.

Objective: To investigate SNc neuromelanin changes in iRBD patients using fully automatic segmentation.

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Article Synopsis
  • The study investigates the role of the cerebellum in paroxysmal kinesigenic dyskinesia (PKD), a condition causing involuntary movements, highlighting the limited understanding of its underlying mechanisms.
  • Twenty-two patients with a specific genetic variant and matched controls participated in a comprehensive neuroimaging study to assess brain structures and connections related to PKD.
  • Results showed significant gray and white matter changes in the cerebellum and other related brain areas, with cerebellar stimulation improving the communication within motor networks, suggesting a potential therapeutic avenue.
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  • Reward sensitivity is a key factor in Tourette disorder, but the impact of delayed rewards has not been thoroughly studied, despite its relevance in various neuropsychiatric conditions.
  • A study involving 54 Tourette patients and 31 healthy controls revealed a subgroup of patients who exhibited higher impulsivity and steeper reward discounting, indicating a greater burden of impulse-control issues.
  • The research found that the pre-supplementary motor area plays a critical role in this delayed reward processing, with its connectivity to other brain regions affecting impulsivity levels and the severity of tics among patients.
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Background: Intermittent theta burst stimulation (iTBS) is a form of repetitive transcranial magnetic stimulation that has shown to be effective in treatment-resistant depression. Through studying the effect of iTBS on healthy subjects, we wished to attain a greater understanding of its impact on the brain. Our objective was to assess whether 10 iTBS sessions altered the neural processing of emotional stimuli, mood and brain anatomy in healthy subjects.

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  • Parkinson's disease leads to a decrease in dopamine function and an increase in iron in specific brain areas, particularly the substantia nigra, indicating potential interconnections between dopamine impairment and iron metabolism changes.
  • A study followed patients with early Parkinson's and REM sleep behavior disorder, using advanced imaging techniques to track levels of neuromelanin, iron, and dopamine over two years.
  • Results indicated that changes in dopamine levels occurred first in the sensorimotor regions, followed by alterations in iron metabolism and finally changes in neuromelanin, reflecting a typical progression pattern of the disease.
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