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Thomas TOURDIAS




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MD: Radiology, Bordeaux (2008)
PhD: Neurosciences, Bordeaux (2011)
Post doc: Stanford University, CA, USA (2013)
Professeur des Universit├ęs - Praticien Hospitalier; PU PH (2016)






66 publication(s) depuis Décembre 2006:


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Les IF indiqués ont été collectés par le Web of Sciences en


25/06/2019 | Cell Rep   IF 7.8
Aquaporin-4 Surface Trafficking Regulates Astrocytic Process Motility and Synaptic Activity in Health and Autoimmune Disease.
Ciappelloni S, Bouchet D, Dubourdieu N, Boue-Grabot E, Kellermayer B, Manso C, Marignier R, Oliet SHR, Tourdias T, Groc L

Abstract:
Astrocytes constantly adapt their ramified morphology in order to support brain cell assemblies. Such plasticity is partly mediated by ion and water fluxes, which rely on the water channel aquaporin-4 (AQP4). The mechanism by which this channel locally contributes to process dynamics has remained elusive. Using a combination of single-molecule and calcium imaging approaches, we here investigated in hippocampal astrocytes the dynamic distribution of the AQP4 isoforms M1 and M23. Surface AQP4-M1 formed small aggregates that contrast with the large AQP4-M23 clusters that are enriched near glutamatergic synapses. Strikingly, stabilizing surface AQP4-M23 tuned the motility of astrocyte processes and favors glutamate synapse activity. Furthermore, human autoantibodies directed against AQP4 from neuromyelitis optica (NMO) patients impaired AQP4-M23 dynamic distribution and, consequently, astrocyte process and synaptic activity. Collectively, it emerges that the membrane dynamics of AQP4 isoform regulate brain cell assemblies in health and autoimmune brain disease targeting AQP4.




19/06/2019 | j Neuroradiol   IF 3.3
Mri Features Of Demyelinating Disease Associated With Anti-Mog Antibodies In Adults.
Deneve M, Biotti D, Patsoura S, Ferrier M, Meluchova Z, Mahieu L, Heran F, Vignal C, Deschamps R, Gout O, Menjot de Champfleur N, Ayrignac X, Dalliere CC, Labauge P, Dulau C, Tourdias T, Dumas H, Cognard C, Brassat D, Bonneville F

Abstract:
The spectrum of Myelin Oligodendrocytes Glycoprotein (MOG) antibody disease constitutes a recently described challenging entity, referring to a relatively new spectrum of autoimmune disorders with antibodies against MOG predominantly involving the optic nerve and spinal cord. The purpose of this article is to describe MRI features of MOG-AD involvement in the optic nerves, spinal cord and the brain of adults.




17/03/2019 | Neuroimage   IF 5.8
Thalamus Optimized Multi Atlas Segmentation (THOMAS): fast, fully automated segmentation of thalamic nuclei from structural MRI.
Su JH, Thomas FT, Kasoff WS, Tourdias T, Choi EY, Rutt BK, Saranathan M

Abstract:
The thalamus and its nuclei are largely indistinguishable on standard T1 or T2 weighted MRI. While diffusion tensor imaging based methods have been proposed to segment the thalamic nuclei based on the angular orientation of the principal diffusion tensor, these are based on echo planar imaging which is inherently limited in spatial resolution and suffers from distortion. We present a multi-atlas segmentation technique based on white-matter-nulled MP-RAGE imaging that segments the thalamus into 12 nuclei with computation times on the order of 10min on a desktop PC; we call this method THOMAS (THalamus Optimized Multi Atlas Segmentation). THOMAS was rigorously evaluated on 7T MRI data acquired from healthy volunteers and patients with multiple sclerosis by comparing against manual segmentations delineated by a neuroradiologist, guided by the Morel atlas. Segmentation accuracy was very high, with uniformly high Dice indices: at least 0.85 for large nuclei like the pulvinar and mediodorsal nuclei and at least 0.7 even for small structures such as the habenular, centromedian, and lateral and medial geniculate nuclei. Volume similarity indices ranged from 0.82 for the smaller nuclei to 0.97 for the larger nuclei. Volumetry revealed that the volumes of the right anteroventral, right ventral posterior lateral, and both right and left pulvinar nuclei were significantly lower in MS patients compared to controls, after adjusting for age, sex and intracranial volume. Lastly, we evaluated the potential of this method for targeting the Vim nucleus for deep brain surgery and focused ultrasound thalamotomy by overlaying the Vim nucleus segmented from pre-operative data on post-operative data. The locations of the ablated region and active DBS contact corresponded well with the segmented Vim nucleus. Our fast, direct structural MRI based segmentation method opens the door for MRI guided intra-operative procedures like thalamotomy and asleep DBS electrode placement as well as for accurate quantification of thalamic nuclear volumes to follow progression of neurological disorders.




12/03/2019 | Neurology   IF 8.7
Acute toxic limbic encephalopathy following glyphosate intoxication.
Planche V, Vergnet S, Auzou N, Bonnet M, Tourdias T, Tison F

Abstract:





27/11/2018 | Mult Scler   IF 5.6
Longitudinal study of functional brain network reorganization in clinically isolated syndrome.
Koubiyr I, Deloire M, Besson P, Coupe P, Dulau C, Pelletier J, Tourdias T, Audoin B, Brochet B, Ranjeva JP, Ruet A

Abstract:
BACKGROUND:: There is a lack of longitudinal studies exploring the topological organization of functional brain networks at the early stages of multiple sclerosis (MS). OBJECTIVE:: This study aims to assess potential brain functional reorganization at rest in patients with CIS (PwCIS) after 1 year of evolution and to characterize the dynamics of functional brain networks at the early stage of the disease. METHODS:: We prospectively included 41 PwCIS and 19 matched healthy controls (HCs). They were scanned at baseline and after 1 year. Using graph theory, topological metrics were calculated for each region. Hub disruption index was computed for each metric. RESULTS:: Hub disruption indexes of degree and betweenness centrality were negative at baseline in patients ( p < 0.05), suggesting brain reorganization. After 1 year, hub disruption indexes for degree and betweenness centrality were still negative ( p < 0.00001), but such reorganization appeared more pronounced than at baseline. Different brain regions were driving these alterations. No global efficiency differences were observed between PwCIS and HCs either at baseline or at 1 year. CONCLUSION:: Dynamic changes in functional brain networks appear at the early stages of MS and are associated with the maintenance of normal global efficiency in the brain, suggesting a compensatory effect.




12/09/2018 | Sci Rep   IF 4
Objective Evaluation of Multiple Sclerosis Lesion Segmentation using a Data Management and Processing Infrastructure.
Commowick O, Istace A, Kain M, Laurent B, Leray F, Simon M, Pop SC, Girard P, Ameli R, Ferre JC, Kerbrat A, Tourdias T, Cervenansky F, Glatard T, Beaumont J, Doyle S, Forbes F, Knight J, Khademi A, Mahbod A, Wang C, McKinley R, Wagner F, Muschelli J, Sweeney E, Roura E, Llado X, Santos MM, Santos WP, Silva-Filho AG, Tomas-Fernandez X, Urien H, Bloch I, Valverde S, Cabezas M, Vera-Olmos FJ, Malpica N, Guttmann C, Vukusic S, Edan G, Dojat M, Styner M, Warfield SK, Cotton F, Barillot C

Abstract:
We present a study of multiple sclerosis segmentation algorithms conducted at the international MICCAI 2016 challenge. This challenge was operated using a new open-science computing infrastructure. This allowed for the automatic and independent evaluation of a large range of algorithms in a fair and completely automatic manner. This computing infrastructure was used to evaluate thirteen methods of MS lesions segmentation, exploring a broad range of state-of-theart algorithms, against a high-quality database of 53 MS cases coming from four centers following a common definition of the acquisition protocol. Each case was annotated manually by an unprecedented number of seven different experts. Results of the challenge highlighted that automatic algorithms, including the recent machine learning methods (random forests, deep learning, ...), are still trailing human expertise on both detection and delineation criteria. In addition, we demonstrate that computing a statistically robust consensus of the algorithms performs closer to human expertise on one score (segmentation) although still trailing on detection scores.




27/02/2018 | Lancet Neurol   IF 28.8
Use of brain diffusion tensor imaging for the prediction of long-term neurological outcomes in patients after cardiac arrest: a multicentre, international, prospective, observational, cohort study.
Velly L, Perlbarg V, Boulier T, Adam N, Delphine S, Luyt CE, Battisti V, Torkomian G, Arbelot C, Chabanne R, Jean B, Di Perri C, Laureys S, Citerio G, Vargiolu A, Rohaut B, Bruder N, Girard N, Silva S, Cottenceau V, Tourdias T, Coulon O, Riou B, Naccache L, Gupta R, Benali H, Galanaud D, Puybasset L

Abstract:
BACKGROUND: Prediction of neurological outcome after cardiac arrest is a major challenge. The aim of this study was to assess whether quantitative whole-brain white matter fractional anisotropy (WWM-FA) measured by diffusion tensor imaging between day 7 and day 28 after cardiac arrest can predict long-term neurological outcome. METHODS: This prospective, observational, cohort study (part of the MRI-COMA study) was done in 14 centres in France, Italy, and Belgium. We enrolled patients aged 18 years or older who had been unconscious for at least 7 days after cardiac arrest into the derivation cohort. The following year, we recruited the validation cohort on the same basis. We also recruited a minimum of five healthy volunteers at each centre for the normalisation procedure. WWM-FA values were compared with standard criteria for unfavourable outcome, conventional MRI sequences (fluid-attenuated inversion recovery and diffusion-weighted imaging), and proton magnetic resonance spectroscopy. The primary outcome was the best achieved Glasgow-Pittsburgh Cerebral Performance Categories (CPC) at 6 months, dichotomised as favourable (CPC 1-2) and unfavourable outcome (CPC 3-5). Prognostication performance was assessed by the area under the receiver operating characteristic (ROC) curves and compared between groups. This study was registered with ClinicalTrials.gov, number NCT00577954. FINDINGS: Between Oct 1, 2006, and June 30, 2014, 185 patients were enrolled in the derivation cohort, of whom 150 had an interpretable multimodal MRI and were included in the analysis. 33 (22%) patients had a favourable neurological outcome at 6 months. Prognostic accuracy, as quantified by the area under the ROC curve, was significantly higher with the normalised WWM-FA value (area under the ROC curve 0.95, 95% CI 0.91-0.98) than with the standard criteria for unfavourable outcome or other MRI sequences. In a subsequent validation cohort of 50 patients (enrolled between April 1, 2015, and March 31, 2016), a normalised WWM-FA value lower than 0.91, set from the derivation cohort, had a negative predictive value of 71.4% (95% CI 41.9-91.6) and a positive predictive value of 100% (90.0-100), with 89.7% sensitivity (75.8-97.1) and 100% specificity (69.1-100) for the prediction of unfavourable outcome. INTERPRETATION: In patients who are unconscious 7 days after cardiac arrest, the normalised WWM-FA value, measured by diffusion tensor imaging, could be used to accurately predict neurological outcome at 6 months. This evidence requires confirmation from future large-scale trials with a strict protocol of withdrawal or limitation-of-care decisions and time window for MRI. FUNDING: French Ministry of Health, French National Agency for Research, Italian Ministry of Health, and Regione Lombardia.




15/02/2018 | J Neurol Sci   IF 2.7
Preliminary evidence of the cerebellar role on cognitive performances in clinically isolated syndrome.
Moroso A, Ruet A, Lamargue-Hamel D, Munsch F, Deloire M, Ouallet JC, Cubizolle S, Charre-Morin J, Saubusse A, Tourdias T, Dousset V, Brochet B

Abstract:
BACKGROUND: Cerebellar and cognitive dysfunction can occur early in clinically isolated syndrome (CIS). Eye tracking is a reliable tool for the evaluation of both subtle cerebellar symptoms and cognitive impairment. OBJECTIVES: To investigate the early cognitive profile using neuropsychological and ocular motor (OM) testing in CIS with and without cerebellar dysfunction with OM testing compared to healthy subjects (HS). METHODS: Twenty-eight patients and 12 HC underwent OM and neuropsychological testing. Cerebellar impairment was defined by the registration of saccadic intrusions and/or at least 10% of dysmetria during ocular motor recording. Visually guided saccade (VGS), memory-guided saccade (MGS) and antisaccade (AS) paradigms were compared to neuropsychological assessments. RESULTS: The group of patients with cerebellar dysfunction (n=16) performed worse on MGS latencies and error rates, and had worse working memory, executive function and information processing speed (IPS) z scores than patients without cerebellar dysfunction. IPS was correlated with the AS error rate in all patients and with the VGS error rate and the MGS final eye position ratio in cerebellar patients. CONCLUSION: Eye tracking is a sensitive tool to assess cognitive and cerebellar dysfunctions in CIS. In CIS patients, cerebellar impairment is associated with working memory, executive functions and IPS slowness.




02/2018 | Muscle Nerve   IF 2.4
Chronic inflammatory demyelinating polyradiculoneuropathy-causing myelopathy.
Mathis S, Duval F, Sole G, Tourdias T, Le Masson G

Abstract:





30/01/2018 | Neuroimage   IF 5.8
Deciphering the microstructure of hippocampal subfields with in vivo DTI and NODDI: Applications to experimental multiple sclerosis.
Crombe A, Planche V, Raffard G, Bourel J, Dubourdieu N, Panatier A, Fukutomi H, Dousset V, Oliet S, Hiba B, Tourdias T

Abstract:
The hippocampus contains distinct populations of neurons organized into separate anatomical subfields and layers with differential vulnerability to pathological mechanisms. The ability of in vivo neuroimaging to pinpoint regional vulnerability is especially important for better understanding of hippocampal pathology at the early stage of neurodegenerative disorders and for monitoring future therapeutic strategies. This is the case for instance in multiple sclerosis whose neurodegenerative component can affect the hippocampus from the early stage. We challenged the capacity of two models, i.e. the classical diffusion tensor imaging (DTI) model and the neurite orientation dispersion and density imaging (NODDI) model, to compute quantitative diffusion MRI that could capture microstructural alterations in the individual hippocampal layers of experimental-autoimmune encephalomyelitis (EAE) mice, the animal model of multiple sclerosis. To achieve this, the hippocampal anatomy of a healthy mouse brain was first explored ex vivo with high resolution DTI and NODDI. Then, 18 EAE mice and 18 control mice were explored 20 days after immunization with in vivo diffusion MRI prior to sacrifice for the histological quantification of neurites and glial markers in each hippocampal layer. Fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD) and mean diffusivity (MD) maps were computed from the DTI model while the orientation dispersion index (ODI), the neurite density index (NDI) and the volume fraction of isotropic diffusivity (isoVF) maps were computed from the NODDI model. We first showed in control mice that color-coded FA and ODI maps can delineate three main hippocampal layers. The quantification of FA, AD, RD, MD, ODI, NDI and isoVF presented differences within these 3 layers, especially within the molecular layer of the dentate gyrus which displayed a specific signature based on a combination of AD (or MD), ODI and NDI. Then, the comparison between EAE and control mice showed a decrease of AD (p=0.036) and of MD (p=0.033) selectively within the molecular layer of EAE mice while NODDI indices did not present any difference between EAE and control mice in any layer. Histological analyses confirmed the differential vulnerability of the molecular layer of EAE mice that exhibited decreased dendritic length and decreased dendritic complexity together with activated microglia. Dendritic length and intersections within the molecular layer were independent contributors to the observed decrease of AD (R(2)=0.37 and R(2)=0.40, p<0.0001) and MD (R(2)=0.41 and R(2)=0.42, p<0.0001). We therefore identified that NODDI maps can help to highlight the internal microanatomy of the hippocampus but NODDI still presents limitations in grey matter as it failed to capture selective dendritic alterations occurring at early stages of a neurodegenerative disease such as multiple sclerosis, whereas DTI maps were significantly altered.