Surface Smoothing: A Way Back in Early Brain

Abstract. In this article we propose to investigate the analogy between early cortical folding process and cortical smoothing by mean curvature flow. First, we introduce a one-parameter model that is able to fit a developmental trajectory as represented in a Volume-Area plot and we propose an efficient optimization strategy for parameter estimation. Second, we validate the model on forty cortical surfaces of preterm newborns by comparing global geometrical indices and trajectories of central sulcus along developmental and simulation time.

Optimizing statistical parametric mapping analysis of 18F-FDG PET in children.

International audienceABSTRACT: BACKGROUND: Statistical parametric mapping (SPM) procedure is an objective tool to analyze 18F-fluoro-2-deoxy-d-glucose-positron-emission tomography (FDG-PET) images and a useful complement to visual analysis. However, SPM requires a comparison to control data set that cannot be obtained in healthy children for ethical reasons. Using adults as controls showed some limitations. The purpose of the present study was to generate and validate a group of pseudo-normal children as a control group for FDG-PET studies in pediatrics. METHODS: FDG-PET images of 47 children (mean +/- SD age 10.2 +/- 3.1 years) with refractory symptomatic (MRI-positive, n = 20) and cryptogenic (MRI-negative, n = 27) focal epilepsy planned for surgery were analyzed using visual and SPM analysis. Performances of SPM analysis were compared using two different control groups: (1) an adult control group consisting of healthy young adults (n = 25, 30.5 +/- 5.8 years, adult PET template) and (2) a pediatric pseudo-control group consisting of patients (n = 24, 10.6 +/- 3.1 years, children PET template) with refractory focal epilepsy; but negative MRI and PET are considered normal not only on visual analysis but also on SPM. RESULTS: Among the 47 children, visual analysis succeeded detecting at least one hypometabolic area in 87% of the cases (interobserver kappa = 0.81). Regarding SPM analysis, the best compromise between sensitivity and specificity was obtained with a threshold of p less than 0.001 as an extent of more than 40 voxels. There was a significant concordance to detect hypometabolic areas between both SPM analyses [kappa (K) = 0.59; p < 0.005] and between both SPM and visual analyses (K = 0.45; p < 0.005), in symptomatic (K = 0.74; p < 0.005) as in cryptogenic patients (K = 0.26; p < 0.01). The pediatric pseudo-control group dramatically improved specificity (97% vs. 89%; p < 0.0001) by increasing the positive predictive value (86% vs. 65%). Sensitivity remained acceptable although it was not better (79% vs. 87%, p = 0.039). The main impact was to reduce by 41% the number of hypometabolic cortical artifacts detected by SPM, especially in the younger epileptic patients, which is a key point in clinical practice. CONCLUSIONS: This age-matched pseudo-control group is a way to optimize SPM analysis of FDG-PET in children with epilepsy. It might also be considered for other brain pathologies in pediatrics in the future

Presurgical language mapping in children with epilepsy: Clinical usefulness of functional magnetic resonance imaging for the planning of cortical stimulation

Purpose: Presurgical language mapping in dominant hemisphere epilepsy to evaluate the risk of postoperative deficit is particularly difficult in children. Extraoperative invasive cortical stimulation can show some areas critical to language, but not all of them, due to scarce sampling, poor cooperation, cortical immaturity, or network reorganization, whereas functional magnetic resonance imaging (fMRI) displays entire networks involved in, but not necessarily critical to, language. In a homogeneous series of children with epilepsy, we compared the contributions of language fMRI and depth electrode stimulations to optimize language mapping. Methods: Eight children (7.5-15.5 years) with left frontal or temporal epilepsy underwent language fMRI and language stimulation with depth electrodes as part of their comprehensive presurgical workup. fMRI data collected during sentence generation were analyzed using statistical parametric mapping (SPM2) (false discovery rate [FDR] p \u3c 0.05). Bipolar stimulations were performed during language production tasks. By coregistering fMRI and postimplantation computed tomography (CT) images, we were able to directly compare the cortical areas identified by both investigations. Key Findings: fMRI during sentence generation robustly showed activation in the whole perisylvian regions with little reorganization (left hemisphere dominant in 7). Of the 184 electrode contacts tested for language, only 8 were positive (language disruption) in three of the seven patients with periictal language impairment and left language dominance. All of the positive contacts colocalized with an fMRI activated cluster, that is, fMRI did not miss any region critical to language (sensitivity = 100%). However, 54 of the 176 negative contacts were within activated clusters (low specificity). Significance: In children with epilepsy, the sensitivity of fMRI during sentence generation allows for the detection of all critical regions displayed by cortical stimulation within the large perisylvian language network, but with a low specificity. It is, therefore, useful to optimize the placement of intracranial electrodes when language mapping is necessary. Systematic planning of the electrode placement according to language fMRI maps should increase the yield of extraoperative cortical stimulation, which appears rather low in children when compared to adults. © 2011 International League Against Epilepsy

Relationships between Regional Radiation Doses and Cognitive Decline in Children Treated with Cranio-Spinal Irradiation for Posterior Fossa Tumors

Pediatric posterior fossa tumor (PFT) survivors who have been treated with cranial radiation therapy often suffer from cognitive impairments that might relate to IQ decline. Radiotherapy (RT) distinctly affects brain regions involved in different cognitive functions. However, the relative contribution of regional irradiation to the different cognitive impairments still remains unclear. We investigated the relationships between the changes in different cognitive scores and radiation dose distribution in 30 children treated for a PFT. Our exploratory analysis was based on a principal component analysis (PCA) and an ordinary least square regression approach. The use of a PCA was an innovative way to cluster correlated irradiated regions due to similar radiation therapy protocols across patients. Our results suggest an association between working memory decline and a high dose (equivalent uniform dose, EUD) delivered to the orbitofrontal regions, whereas the decline of processing speed seemed more related to EUD in the temporal lobes and posterior fossa. To identify regional effects of RT on cognitive functions may help to propose a rehabilitation program adapted to the risk of cognitive impairment

Robust imaging of hippocampal inner structure at 7T: in vivo acquisition protocol and methodological choices

International audienceOBJECTIVE:Motion-robust multi-slab imaging of hippocampal inner structure in vivo at 7T.MATERIALS AND METHODS:Motion is a crucial issue for ultra-high resolution imaging, such as can be achieved with 7T MRI. An acquisition protocol was designed for imaging hippocampal inner structure at 7T. It relies on a compromise between anatomical details visibility and robustness to motion. In order to reduce acquisition time and motion artifacts, the full slab covering the hippocampus was split into separate slabs with lower acquisition time. A robust registration approach was implemented to combine the acquired slabs within a final 3D-consistent high-resolution slab covering the whole hippocampus. Evaluation was performed on 50 subjects overall, made of three groups of subjects acquired using three acquisition settings; it focused on three issues: visibility of hippocampal inner structure, robustness to motion artifacts and registration procedure performance.RESULTS:Overall, T2-weighted acquisitions with interleaved slabs proved robust. Multi-slab registration yielded high quality datasets in 96 % of the subjects, thus compatible with further analyses of hippocampal inner structure.CONCLUSION:Multi-slab acquisition and registration setting is efficient for reducing acquisition time and consequently motion artifacts for ultra-high resolution imaging of the inner structure of the hippocampus

Imager la myéline in vivo dans le cerveau : Que nous apprennent les nouvelles techniques d'IRM chez le nourrisson ?

National audienc

Corrélats anatomo-fonctionnels de l'insuffisance de croissance cérébrale (de l'étude clinique de microcéphalies primitives sévères aux développements méthodologiques en neuroimagerie)

Un adulte porteur de microcéphalie primitive sévère peut avoir le volume cérébral d un enfant sain âgé de 1 an. La constitution de groupes génétiquement homogènes de patients permet d étudier le phénotype spécifique de ces maladies et la façon dont la réduction de volume s installe et modifie l organisation anatomo-fonctionnelle du cerveau. Dans ce travail nous avons : 1) raffiné le spectre phénotypique clinique, radiologique et neuropsychologique associé aux mutations de PQBP1 au sein de la série française des porteurs de maladie de Renpenning ; 2) développé de nouveaux outils d analyse de la gyration corticale afin d explorer la relation allométrique entre volume cérébral et complexité gyrale en population générale et dans 3 groupes de microcéphalies (ASPM, PQBP1 et SAF), permettant une refonte de la notion controversée de simplification gyrale ; 3) initié le développement d un modèle de cinétique de croissance et d une épreuve de mémoire mixte (court et long terme) en IRM fonctionnelle afin d établir de nouveaux endophénotypes en cas de microcéphalie ou de déficience intellectuelle. A l interface entre clinique et neuroimagerie, ce travail multidisciplinaire espère contribuer à une meilleure compréhension des conséquences de l insuffisance de croissance cérébrale au bénéfice de la prise en charge des patients.An adult with severe primary microcephaly may have the same brain volume than a healthy 1-Y/O child. Gathering genetically homogeneous groups of patients enables to study the specific phenotype of each disease and to probe the way volume reduction settles in and modifies both anatomic and functional brain organisation. In this work: 1) we refined the clinical, radiological and neuropsychological spectrum associated with PQBP1 mutations into the French series of Renpenning disease patients ; 2) we developped new tools for the analysis of cortical gyrification to investigate the link between brain volume and gyral complexity in the general population and in 3 groups of microcepahlies (ASPM, PQBP1 and FAS), then updated the disputed concept of simplified gyral pattern ; 3) we started the developpment of a growth kinetics model and of a functional MRI task linking short and long term memories, to estabish new endophenotypes for diseases with either microcephaly or intellectual deficiency. Interfacing clinical and neuroimaging research, this multidisciplinary work hopes to contribute to a further understanding of the consequences of brain growth insufficiency for the sake of patient management.PARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

Imager la myéline in vivo dans le cerveau : Que nous apprennent les nouvelles techniques d'IRM chez le nourrisson ?

National audienc

[Has functional cerebral MRI a clinical future?]

International audienc

Apport pronostique de l' imagerie par résonance magnétique (IRM) de diffusion précoce dans les encéphalites aiguës de l' enfant

Nous avons étudié l apport pronostique en terme de séquelles neurologiques de l IRM de diffusion cérébrale précoce dans les encéphalites aiguës de l enfant. Notre hypothèse de travail était qu une restriction de la diffusion à la phase aiguë, témoignant d un œdème cytotoxique, serait une indication d un pronostic neurologique plus péjoratif qu une diffusion augmentée et a fortiori normale. Les dossiers de 25 patients ont été repris de façon rétrospective, avec analyse de leur IRM cérébrale de diffusion initiale (calcul du coefficient ADC dans 7 régions d intérêt), et leur devenir a été évalué à l aide des données de suivi en consultation, des données concernant leur scolarité et leur prise en charge rééducative, ainsi que par l échelle de Vineland pour 20 d entre eux et l échelle de BRIEF pour 8 d entre eux. Nous avons mis en évidence des corrélations significatives entre type d atteinte à l imagerie de diffusion précoce et devenir neurocognitif des patients, notamment pour le domaine du langage, mais également en terme de scolarité. Notre travail souligne donc l importance de réaliser une séquence de diffusion en IRM précocément dans les encéphalites aiguës de l enfant, et montre également l intérêt d un suivi prolongé de ces patients.PARIS6-Bibl.Pitié-Salpêtrie (751132101) / SudocSudocFranceF