Percutaneous retrograde screwing for stabilisation of acetabular fractures.

OBJECTIVES: To evaluate the results of retrograde percutaneous screw fixation (PSF) in minimally or undisplaced acetabular fractures in a geriatric population. PATIENTS AND METHODS: Between July 1998 and July 2001, 21 consecutive patients with an acetabular fracture underwent fluoroscopic guided percutaneous fixation. The mean age was 81 years (range 67--90 years). In all cases, the fracture was minimally or undisplaced (<2mm). Two cannulated cancellous 7.3mm screws were inserted in a retrograde fashion to stabilise the posterior and the anterior column. Bed to chair transfer began after 24h. Weight bearing as tolerated was allowed at 4 weeks. RESULTS: Eighteen patients were reviewed at a mean of 3.5 years (range 2--5 years). Soft tissue dissection was minimal. There were no intraoperative or postoperative complications. At the latest follow-up there was no radiographical evidence of secondary displacement of fragments, degenerative changes, or screw failure. Fractures healed at a mean time of 12 weeks (range 8--15 weeks). Clinical results were satisfactory in 17 patients. CONCLUSION: Our results show that percutaneous screw fixation under fluoroscopic control is a safe technique to treat some pattern of acetabular fracture.

Demyelination of superficial white matter in early Alzheimer's disease: a magnetization transfer imaging study.

Assuming selective vulnerability of short association U-fibers in early Alzheimer's disease (AD), we quantified demyelination of the surface white matter (dSWM) with magnetization transfer ratio (MTR) in 15 patients (Clinical Dementia Rating Scale [CDR] 0.5-1; Functional Assessment Staging [FAST]: 3-4) compared with 15 controls. MTRs were computed for 39 areas in each hemisphere. We found a bilateral MTR decrease in the temporal, cingulate, parietal, and prefrontal areas. With linear discriminant analysis, we successfully classified all the participants with 3 variates including the cuneus, parahippocampal, and superior temporal regions of the left hemisphere. The pattern of dSWM changed with the age of AD onset. In early onset patients, we found bilateral posterior demyelination spreading to the temporal areas in the left hemisphere. The late onset patients showed a distributed bilateral pattern with the temporal and cingulate areas strongly affected. A correlation with Mini Mental State Examination (MMSE), Lexis, and memory tests revealed the dSWM impact on cognition. A specific landscape of dSWM in early AD shows the potential of MTR imaging as an in vivo biomarker superior to currently used techniques.

Traitement mini-invasif sous contrôle scanner et fluoroscopique de la lyse isthmique vertébrale : une nouvelle technique.

Objectifs: Evaluer la faisabilité, les résultats préliminaires à court et long terme du vissage percutané de vissage trans -isthmique sous anesthésie locale et contrôle scannerdes lyses isthmiques de bas grades.Matériels et méthodes: Etude prospective monocentrique réalisée sur 10 patients ayant une lyse isthmique grade 1 et 2 résistant au traitement médical conventionnel. Une évaluationclinique était réalisée à un mois, 3 mois, 6 mois et un an post-opératoire par un évaluateur indépendant. L'indication est posée en concertation avec le service dechirurgie orthopédique.Résultats: Les lyses isthmiques étaient situées en L5-S1 avec 6 grades 1 et 4 grades 2. L'échelle analogique de la douleur (VAS) variait de 6 a 9 avec une moyenne de 7,8.L'indication opératoire chirurgicale était posée pour tous les patients par arthrodèse postérieure lombo -sacree. Pour chaque patient 2 vis étaient positionnées soitun total de 20 vis. Un suivi clinique était réalisé de 28 a 36 mois. L'EVA et ODI diminuaient de 7,8 +/- 1,7 à 1,9 +/- 1,2 et de 62,3 +/- 17,2 à 15,1 +/- 6,0respectivement. L'ensemble des résultats était stable dans le temps en particulier à long terme.Conclusion: La fixation précise de la lyse isthmique améliore la symptomatologie et probablement évite un glissement vertébral plus important , un suivi à plus long terme surune serie de patients plus importante devrait confirmer cette hypothèse.

Rapid disease emergence through horizontal gene transfer between eukaryotes.

Among different species of eukaryotes, the extent and evolutionary significance of horizontal gene transfer remains poorly understood. A newly published study by Friesen and colleagues indicates that a recent gene transfer between two species of fungi has enabled the recipient to rapidly acquire high virulence on wheat. The study highlights a mechanism by which diseases can suddenly emerge, but also brings up the controversial issues of how horizontal gene transfer occurs and whether fungal incompatibility barriers to gene flow are more 'leaky' than was previously thought.

Interhemispheric visual integration in humans explored by multimodal brain imaging

Résumé: Les récents progrès techniques de l'imagerie cérébrale non invasives ont permis d'améliorer la compréhension des différents systèmes fonctionnels cérébraux. Les approches multimodales sont devenues indispensables en recherche, afin d'étudier dans sa globalité les différentes caractéristiques de l'activité neuronale qui sont à la base du fonctionnement cérébral. Dans cette étude combinée d'imagerie par résonance magnétique fonctionnelle (IRMf) et d'électroencéphalographie (EEG), nous avons exploité le potentiel de chacune d'elles, soit respectivement la résolution spatiale et temporelle élevée. Les processus cognitifs, de perception et de mouvement nécessitent le recrutement d'ensembles neuronaux. Dans la première partie de cette thèse nous étudions, grâce à la combinaison des techniques IRMf et EEG, la réponse des aires visuelles lors d'une stimulation qui demande le regroupement d'éléments cohérents appartenant aux deux hémi-champs visuels pour en faire une seule image. Nous utilisons une mesure de synchronisation (EEG de cohérence) comme quantification de l'intégration spatiale inter-hémisphérique et la réponse BOLD (Blood Oxygenation Level Dependent) pour évaluer l'activité cérébrale qui en résulte. L'augmentation de la cohérence de l'EEG dans la bande beta-gamma mesurée au niveau des électrodes occipitales et sa corrélation linéaire avec la réponse BOLD dans les aires de VP/V4, reflète et visualise un ensemble neuronal synchronisé qui est vraisemblablement impliqué dans le regroupement spatial visuel. Ces résultats nous ont permis d'étendre la recherche à l'étude de l'impact que le contenu en fréquence des stimuli a sur la synchronisation. Avec la même approche, nous avons donc identifié les réseaux qui montrent une sensibilité différente à l'intégration des caractéristiques globales ou détaillées des images. En particulier, les données montrent que l'implication des réseaux visuels ventral et dorsal est modulée par le contenu en fréquence des stimuli. Dans la deuxième partie nous avons a testé l'hypothèse que l'augmentation de l'activité cérébrale pendant le processus de regroupement inter-hémisphérique dépend de l'activité des axones calleux qui relient les aires visuelles. Comme le Corps Calleux présente une maturation progressive pendant les deux premières décennies, nous avons analysé le développement de la fonction d'intégration spatiale chez des enfants âgés de 7 à 13 ans et le rôle de la myelinisation des fibres calleuses dans la maturation de l'activité visuelle. Nous avons combiné l'IRMf et la technique de MTI (Magnetization Transfer Imaging) afin de suivre les signes de maturation cérébrale respectivement sous l'aspect fonctionnel et morphologique (myelinisation). Chez lés enfants, les activations associées au processus d'intégration entre les hémi-champs visuels sont, comme chez l'adulte, localisées dans le réseau ventral mais se limitent à une zone plus restreinte. La forte corrélation que le signal BOLD montre avec la myelinisation des fibres du splenium est le signe de la dépendance entre la maturation des fonctions visuelles de haut niveau et celle des connections cortico-corticales. Abstract: Recent advances in non-invasive brain imaging allow the visualization of the different aspects of complex brain dynamics. The approaches based on a combination of imaging techniques facilitate the investigation and the link of multiple aspects of information processing. They are getting a leading tool for understanding the neural basis of various brain functions. Perception, motion, and cognition involve the formation of cooperative neuronal assemblies distributed over the cerebral cortex. In this research, we explore the characteristics of interhemispheric assemblies in the visual brain by taking advantage of the complementary characteristics provided by EEG (electroencephalography) and fMRI (Functional Magnetic Resonance Imaging) techniques. These are the high temporal resolution for EEG and high spatial resolution for fMRI. In the first part of this thesis we investigate the response of the visual areas to the interhemispheric perceptual grouping task. We use EEG coherence as a measure of synchronization and BOLD (Blood Oxygenar tion Level Dependent) response as a measure of the related brain activation. The increase of the interhemispheric EEG coherence restricted to the occipital electrodes and to the EEG beta band and its linear relation to the BOLD responses in VP/V4 area points to a trans-hemispheric synchronous neuronal assembly involved in early perceptual grouping. This result encouraged us to explore the formation of synchronous trans-hemispheric networks induced by the stimuli of various spatial frequencies with this multimodal approach. We have found the involvement of ventral and medio-dorsal visual networks modulated by the spatial frequency content of the stimulus. Thus, based on the combination of EEG coherence and fMRI BOLD data, we have identified visual networks with different sensitivity to integrating low vs. high spatial frequencies. In the second part of this work we test the hypothesis that the increase of brain activity during perceptual grouping depends on the activity of callosal axons interconnecting the visual areas that are involved. To this end, in children of 7-13 years, we investigated functional (functional activation with fMRI) and morphological (myelination of the corpus callosum with Magnetization Transfer Imaging (MTI)) aspects of spatial integration. In children, the activation associated with the spatial integration across visual fields was localized in visual ventral stream and limited to a part of the area activated in adults. The strong correlation between individual BOLD responses in .this area and the myelination of the splenial system of fibers points to myelination as a significant factor in the development of the spatial integration ability.

The sheeping technique or how to avoid exchange maneuvers.

INTRODUCTION: The arteries of bifurcation aneurysms are sometimes so angulated or tortuous that an exchange maneuver is necessary to catheterize them with a balloon or stent delivery catheter. Because of the risk of distal wire perforation associated with exchange maneuvers, we sought to find an alternative technique. METHODS: Our experience shows that a microcatheter tends to preferentially follow a previously placed microcatheter, even if the initial catheterization might be challenging. Accessing an artery with two microcatheters simultaneously may thus be an alternative to an exchange maneuver. Because of this tendency for catheters to behave like sheep following one another, we named this method the sheeping technique (ST). The ST consists of (a) first placing a 1.7 French microcatheter into the division branch requiring balloon or stent protection to straighten the course of the arteries in order to facilitate and (b) positioning in the same artery of a larger and stiffer balloon or stent microcatheter. Once the second balloon or stent microcatheter is in place, the first microcatheter can be pulled back and used to coil the aneurysm. RESULTS: Between January 2009 and December 2012, The ST was successfully used in 208/246 procedures (85 %). Conversion to an exchange maneuver was necessary in 38/246 (15 %). There were no arterial perforations or ischemic events related to the handling of both microcatheters. CONCLUSION: The sheeping technique may improve safety by replacing the need for an exchange maneuver during difficult balloon- or stent-assisted coiling.

Identification of different heart tissues from MRI C-SENC images using an unsupervised multi-stage fuzzy clustering technique.

PURPOSE: To objectively characterize different heart tissues from functional and viability images provided by composite-strain-encoding (C-SENC) MRI. MATERIALS AND METHODS: C-SENC is a new MRI technique for simultaneously acquiring cardiac functional and viability images. In this work, an unsupervised multi-stage fuzzy clustering method is proposed to identify different heart tissues in the C-SENC images. The method is based on sequential application of the fuzzy c-means (FCM) and iterative self-organizing data (ISODATA) clustering algorithms. The proposed method is tested on simulated heart images and on images from nine patients with and without myocardial infarction (MI). The resulting clustered images are compared with MRI delayed-enhancement (DE) viability images for determining MI. Also, Bland-Altman analysis is conducted between the two methods. RESULTS: Normal myocardium, infarcted myocardium, and blood are correctly identified using the proposed method. The clustered images correctly identified 90 +/- 4% of the pixels defined as infarct in the DE images. In addition, 89 +/- 5% of the pixels defined as infarct in the clustered images were also defined as infarct in DE images. The Bland-Altman results show no bias between the two methods in identifying MI. CONCLUSION: The proposed technique allows for objectively identifying divergent heart tissues, which would be potentially important for clinical decision-making in patients with MI.

High-level transgene expression by homologous recombination-mediated gene transfer.

Gene transfer and expression in eukaryotes is often limited by a number of stably maintained gene copies and by epigenetic silencing effects. Silencing may be limited by the use of epigenetic regulatory sequences such as matrix attachment regions (MAR). Here, we show that successive transfections of MAR-containing vectors allow a synergistic increase of transgene expression. This finding is partly explained by an increased entry into the cell nuclei and genomic integration of the DNA, an effect that requires both the MAR element and iterative transfections. Fluorescence in situ hybridization analysis often showed single integration events, indicating that DNAs introduced in successive transfections could recombine. High expression was also linked to the cell division cycle, so that nuclear transport of the DNA occurs when homologous recombination is most active. Use of cells deficient in either non-homologous end-joining or homologous recombination suggested that efficient integration and expression may require homologous recombination-based genomic integration of MAR-containing plasmids and the lack of epigenetic silencing events associated with tandem gene copies. We conclude that MAR elements may promote homologous recombination, and that cells and vectors can be engineered to take advantage of this property to mediate highly efficient gene transfer and expression.

A simple bypass technique for superior vena cava reconstruction.

Superior vena cava (SVC) clamping can be required during thoracic surgery for SVC replacement or repair. In such cases, bypass techniques can be necessary to avoid hemodynamic instability, cerebral venous hypertension and hypoperfusion. Here, we report a novel and simple SVC bypass technique which does not require full systemic heparinization, specialized cannulation techniques or pumping devices and which can be applied percutaneously in the preoperative phase or intraoperatively. The preoperative shunt consisted in two Swan-Ganz catheters inserted in the jugular and femoral veins and connected by perfusion tubing with a three way stopcock. The intraoperative shunt consisted of a Pruitt(®)-catheter inserted in the left innominate vein and connected to a femoral Swan-Ganz catheter by perfusion tubing. We validated our system in seven patients undergoing SVC reconstruction. We monitored the systemic arterial blood pressures, the heart rate and vasoactive peptide requirements throughout the procedure. We also determined the neurological status and the in-hospital morbidity and mortality for each patient. Using this bypass, SVC clamping caused no hemodynamic instability, no neurological impairments and no in-hospital complications or deaths. This simple temporary SVC bypass procedure is safe and avoids hemodynamic instability and cerebral venous hypertension.