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Thomas TOURDIAS




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






70 publication(s) depuis Décembre 2006:


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01/07/2017 | Brain   IF 11.8
Thalamic alterations remote to infarct appear as focal iron accumulation and impact clinical outcome.
Kuchcinski G, Munsch F, Lopes R, Bigourdan A, Su J, Sagnier S, Renou P, Pruvo JP, Rutt BK, Dousset V, Sibon I, Tourdias T

Abstract:
See Duering and Schmidt (doi:10.1093/awx135) for a scientific commentary on this article.Thalamic alterations have been observed in infarcts initially sparing the thalamus but interrupting thalamo-cortical or cortico-thalamic projections. We aimed at extending this knowledge by demonstrating with in vivo imaging sensitive to iron accumulation, one marker of neurodegeneration, that (i) secondary thalamic alterations are focally located in specific thalamic nuclei depending on the initial infarct location; and (ii) such secondary alterations can contribute independently to the long-term outcome. To tackle this issue, 172 patients with an infarct initially sparing the thalamus were prospectively evaluated clinically and with magnetic resonance imaging to quantify iron through R2* map at 24-72 h and at 1-year follow-up. An asymmetry index was used to compare R2* within the thalamus ipsilateral versus contralateral to infarct and we focused on the 95th percentile of R2* as a metric of high iron content. Spatial distribution within the thalamus was analysed on an average R2* map from the entire cohort. The asymmetry index of the 95th percentile within individual nuclei (medio-dorsal, pulvinar, lateral group) were compared according to the initial infarct location in simple and multiple regression analyses and using voxel-based lesion-symptom mapping. Associations between the asymmetry index of the 95th percentile and functional, cognitive and emotional outcome were calculated in multiple regression models. We showed that R2* was not modified at 24-72 h but showed heterogeneous increase at 1 year mainly within the medio-dorsal and pulvinar nuclei. The asymmetry index of the 95th percentile within the medio-dorsal nucleus was significantly associated with infarcts involving anterior areas (frontal P = 0.05, temporal P = 0.02, lenticular P = 0.01) while the asymmetry index of the 95th percentile within the pulvinar nucleus was significantly associated with infarcts involving posterior areas (parietal P = 0.046, temporal P < 0.001) independently of age, gender and infarct volume, which was confirmed by voxel-based lesion-symptom mapping. The asymmetry index of the 95th percentile within the entire thalamus at 1 year was independently associated with poor functional outcome (P = 0.04), poor cognitive outcome (P = 0.03), post-stroke anxiety (P = 0.04) and post-stroke depression (P = 0.02). We have therefore identified that iron accumulates within the thalamus ipsilateral to infarct after a delay with a focal distribution that is strongly linked to the initial infarct location (in relation with the pattern of connectivity between thalamic nuclei and cortical areas or deep nuclei), which independently contributes to functional, cognitive and emotional outcome.




2017 | PLoS ONE   IF 2.8
Lesions in deep gray nuclei after severe traumatic brain injury predict neurologic outcome.
Clarencon F, Bardinet E, Martinerie J, Pelbarg V, Menjot de Champfleur N, Gupta R, Tollard E, Soto-Ares G, Ibarrola D, Schmitt E, Tourdias T, Degos V, Yelnik J, Dormont D, Puybasset L, Galanaud D

Abstract:
PURPOSE: This study evaluates the correlation between injuries to deep gray matter nuclei, as quantitated by lesions in these nuclei on MR T2 Fast Spin Echo (T2 FSE) images, with 6-month neurological outcome after severe traumatic brain injury (TBI). MATERIALS AND METHODS: Ninety-five patients (80 males, mean age = 36.7y) with severe TBI were prospectively enrolled. All patients underwent a MR scan within the 45 days after the trauma that included a T2 FSE acquisition. A 3D deformable atlas of the deep gray matter was registered to this sequence; deep gray matter lesions (DGML) were evaluated using a semi-quantitative classification scheme. The 6-month outcome was dichotomized into unfavorable (death, vegetative or minimally conscious state) or favorable (minimal or no neurologic deficit) outcome. RESULTS: Sixty-six percent of the patients (63/95) had both satisfactory registration of the 3D atlas on T2 FSE and available clinical follow-up. Patients without DGML had an 89% chance (P = 0.0016) of favorable outcome while those with bilateral DGML had an 80% risk of unfavorable outcome (P = 0.00008). Multivariate analysis based on DGML accurately classified patients with unfavorable neurological outcome in 90.5% of the cases. CONCLUSION: Lesions in deep gray matter nuclei may predict long-term outcome after severe TBI with high sensitivity and specificity.




2017 | PLoS ONE   IF 2.8
Microstructural analyses of the posterior cerebellar lobules in relapsing-onset multiple sclerosis and their implication in cognitive impairment.
Moroso A, Ruet A, Lamargue-Hamel D, Munsch F, Deloire M, Coupe P, Charre-Morin J, Saubusse A, Ouallet JC, Planche V, Tourdias T, Dousset V, Brochet B

Abstract:
BACKGROUND: The posterior cerebellar lobules seem to be the anatomical substrate of cognitive cerebellar processes, but their microstructural alterations in multiple sclerosis (MS) remain unclear. OBJECTIVES: To correlate diffusion metrics in lobules VI to VIIIb in persons with clinically isolated syndrome (PwCIS) and in cognitively impaired persons with MS (CIPwMS) with their cognitive performances. METHODS: Sixty-nine patients (37 PwCIS, 32 CIPwMS) and 36 matched healthy subjects (HS) underwent 3T magnetic resonance imaging, including 3D T1-weighted and diffusion tensor imaging (DTI). Fractional anisotropy (FA) and mean diffusivity (MD) were calculated within each lobule and in the cerebellar peduncles. We investigated the correlations between cognitive outcomes and the diffusion parameters of cerebellar sub-structures and performed multiple linear regression analysis to predict cognitive disability. RESULTS: FA was generally lower and MD was higher in the cerebellum and specifically in the vermis Crus II, lobules VIIb and VIIIb in CIPwMS compared with PwCIS and HS. In hierarchical regression analyses, 31% of the working memory z score variance was explained by FA in the left lobule VI and in the left superior peduncle. Working memory was also associated with MD in the vermis Crus II. FA in the left lobule VI and right VIIIa predicted part of the information processing speed (IPS) z scores. CONCLUSION: DTI indicators of cerebellar microstructural damage were associated with cognitive deficits in MS. Our results suggested that cerebellar lobular alterations have an impact on attention, working memory and IPS.




2017 | Front Aging Neurosci   IF 3.6
Gait Change Is Associated with Cognitive Outcome after an Acute Ischemic Stroke.
Sagnier S, Renou P, Olindo S, Debruxelles S, Poli M, Rouanet F, Munsch F, Tourdias T, Sibon I

Abstract:
Background: Cognition and gait have often been studied separately after stroke whereas it has been suggested that these two domains could interact through a cognitive-motor interference. Objective: To evaluate the influence of gait changes on cognitive outcome after an ischemic stroke (IS). Methods: We conducted a prospective and monocentric study including patients admitted for an acute supratentorial IS with a National Institute of Health Stroke Score



2017 | Brain   IF 11.8
Thalamic alterations remote to infarct appear as focal iron accumulation and impact clinical outcome
Kuchcinski G, Munsch F, Lopes R, Bigourdan A, Su J, Sagnier S, Renou P, Pruvo JP, Rutt BK, Dousset V, Tourdias T

Abstract:





01/12/2016 | Invest Ophthalmol Vis Sci   IF 3.8
Optic Radiations Microstructural Changes in Glaucoma and Association With Severity: A Study Using 3Tesla-Magnetic Resonance Diffusion Tensor Imaging.
Tellouck L, Durieux M, Coupe P, Cougnard-Gregoire A, Tellouck J, Tourdias T, Munsch F, Garrigues A, Helmer C, Malet F, Dartigues JF, Dousset V, Delcourt C, Schweitzer C

Abstract:
Purpose: To compare microstructural changes along the optical radiations and brain structure volumes between glaucoma and control subjects using in vivo magnetic resonance imaging and to analyze their association with severity of the disease. Methods: A total of 50 open-angle glaucoma subjects and 50 healthy age- and sex-matched controls underwent detailed ophthalmologic examinations (including visual field testing [VF], funduscopy, and spectral-domain optical coherence tomography) as well as diffusion tensor imaging (DTI) using 3.0-Tesla magnetic resonance imaging. Fractional anisotropy (FA), mean diffusivity, radial diffusivity (RD), and axial diffusivity (AD) were quantified semiautomatically along the optical radiations. DTI parameters and volumes of specific brain structures were compared between cases and controls using conditional logistic regression. Association between DTI metrics and the severity of the disease was studied using linear mixed regression analyses. Results: In glaucoma subjects, optic radiations FA was significantly lower (0.57 vs. 0.59; P = 0.02) and RD was significantly higher (52.78 10-5 mm2/s vs. 49.74 10-5 mm2/s; P = 0.03) than in controls. Optic radiations FA was significantly correlated with homolateral functional and structural damage of glaucoma (mean deviation of VF [P = 0.03], retinal nerve fiber layer thickness [P = 0.03], vertical cup to disc ratio [P = 0.0007]). Volume and DTI parameters of other brain structures (including hippocampus) were not significantly different between glaucoma patients and controls. Conclusions: We evidenced microstructural modifications along visual pathways of glaucoma patients and these alterations were correlated with disease severity. The association of glaucoma with other neurodegenerative alterations would need further exploration and a prospective follow-up of our cohort of subjects. (ClinicalTrials.gov number, NCT01621841).




12/11/2016 | Brain Behav Immun   IF 6.2
Selective dentate gyrus disruption causes memory impairment at the early stage of experimental multiple sclerosis.
Planche V, Panatier A, Hiba B, Ducourneau EG, Raffard G, Dubourdieu N, Maitre M, Leste-Lasserre T, Brochet B, Dousset V, Desmedt A, Oliet SH, Tourdias T

Abstract:
Memory impairment is an early and disabling manifestation of multiple sclerosis whose anatomical and biological substrates are still poorly understood. We thus investigated whether memory impairment encountered at the early stage of the disease could be explained by a differential vulnerability of particular hippocampal subfields. By using experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis, we identified that early memory impairment was associated with selective alteration of the dentate gyrus as pinpointed in vivo with diffusion-tensor-imaging (DTI). Neuromorphometric analyses and electrophysiological recordings confirmed dendritic degeneration, alteration in glutamatergic synaptic transmission and impaired long-term synaptic potentiation selectively in the dentate gyrus, but not in CA1, together with a more severe pattern of microglial activation in this subfield. Systemic injections of the microglial inhibitor minocycline prevented DTI, morphological, electrophysiological and behavioral impairments in EAE-mice. Furthermore, daily infusions of minocycline specifically within the dentate gyrus were sufficient to prevent memory impairment in EAE-mice while infusions of minocycline within CA1 were inefficient. We conclude that early memory impairment in EAE is due to a selective disruption of the dentate gyrus associated with microglia activation. These results open new pathophysiological, imaging, and therapeutic perspectives for memory impairment in multiple sclerosis.




27/10/2016 | J Neurol Neurosurg Psychiatry   IF 8.3
Posterior lobules of the cerebellum and information processing speed at various stages of multiple sclerosis.
Moroso A, Ruet A, Lamargue-Hamel D, Munsch F, Deloire M, Coupe P, Ouallet JC, Planche V, Moscufo N, Meier DS, Tourdias T, Guttmann CR, Dousset V, Brochet B

Abstract:
BACKGROUND: Cerebellar damage has been implicated in information processing speed (IPS) impairment associated with multiple sclerosis (MS) that might result from functional disconnection in the frontocerebellar loop. Structural alterations in individual posterior lobules, in which cognitive functioning seems preponderant, are still unknown. Our aim was to investigate the impact of grey matter (GM) volume alterations in lobules VI to VIIIb on IPS in persons with clinically isolated syndrome (PwCIS), MS (PwMS) and healthy subjects (HS). METHODS: 69 patients (37 PwCIS, 32 PwMS) and 36 HS underwent 3 T MRI including 3-dimensional T1-weighted MRIs. Cerebellum lobules were segmented using SUIT V.3.0 to estimate their normalised GM volume. Neuropsychological testing was performed to assess IPS and main cognitive functions. RESULTS: Normalised GM volumes were significantly different between PwMS and HS for the right (p<0.001) and left lobule VI (p<0.01), left crus I, right VIIb and entire cerebellum (p<0.05 for each comparison) and between PwMS and PwCIS for all lobules in subregions VI and left crus I (p<0.05). IPS, attention and working memory were impaired in PwMS compared with PwCIS. In the whole population of patients (PwMS and PwCIS), GM loss in vermis VI (R2=0.36; p<0.05 when considering age and T2 lesion volume as covariates) were associated with IPS impairment. CONCLUSIONS: GM volume decrease in posterior lobules (especially vermis VI) was associated with reduced IPS. Our results suggest a significant impact of posterior lobules pathology in corticocerebellar loop disruption resulting in automation and cognitive optimisation lack in MS. TRIAL REGISTRATION: Clinicaltrail NCT01207856, NCT01865357; Pre-results.




25/10/2016 | Mult Scler   IF 5.6
Hippocampal microstructural damage correlates with memory impairment in clinically isolated syndrome suggestive of multiple sclerosis.
Planche V, Ruet A, Coupe P, Lamargue-Hamel D, Deloire M, Pereira B, Manjon JV, Munsch F, Moscufo N, Meier DS, Guttmann CR, Dousset V, Brochet B, Tourdias T

Abstract:
OBJECTIVE: We investigated whether diffusion tensor imaging (DTI) could reveal early hippocampal damage and clinically relevant correlates of memory impairment in persons with clinically isolated syndrome (CIS) suggestive of multiple sclerosis (MS). METHODS: A total of 37 persons with CIS, 32 with MS and 36 controls prospectively included from 2011 to 2014 were tested for cognitive performances and scanned with 3T-magnetic resonance imaging (MRI) to assess volumetric and DTI changes within the hippocampus, whole brain volume and T2-lesion load. RESULTS: While there was no hippocampal atrophy in the CIS group, hippocampal fractional anisotropy (FA) was significantly decreased compared to controls. Decrease in hippocampal FA together with increased mean diffusivity (MD) was even more prominent in MS patients. In CIS, hippocampal MD was correlated with episodic verbal memory performance (r = -0.57, p = 0.0002 and odds ratio (OR) = 0.058, 95% confidence interval (CI) = 0.0057-0.59, p = 0.016 adjusted for age, gender, depression and T2-lesion load), but not with cognitive tasks unrelated to hippocampal functions. Hippocampal MD was the only variable discriminating memory-impaired from memory-preserved persons with CIS (area under the curve (AUC) = 0.77, sensitivity = 90.0%, specificity = 70.3%, positive predictive value (PPV) = 52.9%, negative predictive value (NPV) = 95.0%). CONCLUSION: DTI alterations within the hippocampus might reflect early neurodegenerative processes that are correlated with episodic memory performance, discriminating persons with CIS according to their memory status.




30/06/2016 | AJNR Am J Neuroradiol   IF 3.3
Cervical Spinal Cord DTI Is Improved by Reduced FOV with Specific Balance between the Number of Diffusion Gradient Directions and Averages.
Crombe A, Alberti N, Hiba B, Uettwiller M, Dousset V, Tourdias T

Abstract:
BACKGROUND AND PURPOSE: Reduced-FOV DTI is promising for exploring the cervical spinal cord, but the optimal set of parameters needs to be clarified. We hypothesized that the number of excitations should be favored over the number of diffusion gradient directions regarding the strong orientation of the cord in a single rostrocaudal axis. MATERIALS AND METHODS: Fifteen healthy individuals underwent cervical spinal cord MR imaging at 3T, including an anatomic 3D-Multi-Echo Recombined Gradient Echo, high-resolution full-FOV DTI with a NEX of 3 and 20 diffusion gradient directions and 5 sets of reduced-FOV DTIs differently balanced in terms of NEX/number of diffusion gradient directions: (NEX/number of diffusion gradient directions = 3/20, 5/16, 7/12, 9/9, and 12/6). Each DTI sequence lasted 4 minutes 30 seconds, an acceptable duration, to cover C1-C4 in the axial plane. Fractional anisotropy maps and tractograms were reconstructed. Qualitatively, 2 radiologists rated the DTI sets blinded to the sequence. Quantitatively, we compared distortions, SNR, variance of fractional anisotropy values, and numbers of detected fibers. RESULTS: Qualitatively, reduced-FOV DTI sequences with a NEX of >/=5 were significantly better rated than the full-FOV DTI and the reduced-FOV DTI with low NEX (N = 3) and a high number of diffusion gradient directions (D = 20). Quantitatively, the best trade-off was reached by the reduced-FOV DTI with a NEX of 9 and 9 diffusion gradient directions, which provided significantly fewer artifacts, higher SNR on trace at b = 750 s/mm2 and an increased number of fibers tracked while maintaining similar fractional anisotropy values and dispersion. CONCLUSIONS: Optimized reduced-FOV DTI improves spinal cord imaging. The best compromise was obtained with a NEX of 9 and 9 diffusion gradient directions, which emphasizes the need for increasing the NEX at the expense of the number of diffusion gradient directions for spinal cord DTI contrary to brain DTI.