Case report of MR perfusion imaging in Sinking Skin Flap Syndrome: growing evidence for hemodynamic impairment

<p>Abstract</p> <p>Background</p> <p>The syndrome of the sinking skin flap (SSSF) with delayed sensorimotor deficits after craniectomy is not well known and often neglected. Among various postulated causes, there is evidence that disturbed brain perfusion may be related to the observed symptoms, and that cranioplasty reliably alleviates these symptoms. We report a case of sinking skin flap syndrome (SSFS) with recovery from neurological sensorimotor deficits after cranioplasty correlated with pre- and postsurgical MR brain perfusion studies.</p> <p>Case Presentation</p> <p>A 42-year-old woman presented with slowly progressive sensorimotor paresis of her left arm after decompressive extensive craniectomy due to subarachnoid hemorrhage four months ago. Her right cranium showed a "sinking skin flap". After cranioplastic repair of her skull defect, the patient fully recovered from her symptoms. Before cranioplasty, reduced brain perfusion in the right central cortical region was observed in MR-perfusion images. After cranioplasty, a marked increase in brain perfusion was observed which correlated with objective clinical recovery.</p> <p>Conclusion</p> <p>There is increasing evidence that impaired blood flow is responsible for delayed motor deficits in patients with sinking skin flap syndrome in the area of compressed brain regions. Symptoms should be evaluated by brain perfusion imaging complementing surgical decision-making.</p

Comparisons of observed and modelled lake δ18O variability

With the substantial number of lake sediment δ18O records published in recent decades, a quantitative, process-based understanding of these systems can increase our understanding of past climate change. We test mass balance models of lake water δ18O variability against five years of monthly monitoring data from lakes with different hydrological characteristics, in the East-Midlands region of the UK, and the local isotope composition of precipitation. These mass balance models can explain up to 74% of the measured lake water isotope variability. We investigate the sensitivity of the model to differing calculations of evaporation amount, the amount of groundwater, and to different climatic variables. We show there is only a small range of values for groundwater exchange flux that can produce suitable lake water isotope compositions and that variations in evaporation and precipitation are both required to produce recorded isotope variability in lakes with substantial evaporative water losses. We then discuss the potential for this model to be used in a long-term, palaeo-scenario. This study demonstrates how long term monitoring of a lake system can lead to the development of robust models of lake water isotope compositions. Such systematics-based explanations allow us to move from conceptual, to more quantified reconstructions of past climates and environments

The p.Arg435His Variation of IgG3 With High Affinity to FcRn Is Associated With Susceptibility for Pemphigus Vulgaris—Analysis of Four Different Ethnic Cohorts

IgG3 is the IgG subclass with the strongest effector functions among all four IgG subclasses and the highest degree of allelic variability among all constant immunoglobulin genes. Due to its genetic position, IgG3 is often the first isotype an antibody switches to before IgG1 or IgG4. Compared with the other IgG subclasses, it has a reduced half-life which is probably connected to a decreased affinity to the neonatal Fc receptor (FcRn). However, a few allelic variants harbor an amino acid replacement of His435 to Arg that reverts the half-life of the resulting IgG3 to the same level as the other IgG subclasses. Because of its functional impact, we hypothesized that the p.Arg435His variation could be associated with susceptibility to autoantibody-mediated diseases like pemphigus vulgaris (PV) and bullous pemphigoid (BP). Using a set of samples from German, Turkish, Egyptian, and Iranian patients and controls, we were able to demonstrate a genetic association of the p.Arg435His variation with PV risk, but not with BP risk. Our results suggest a hitherto unknown role for the function of IgG3 in the pathogenesis of PV

Modelling the response of deep foundations under oblique loading

Deep foundations are slender pile elements used to transfer loads from structures into deeper soil strata below the ground. Deep foundations have a variety of loads including axial, lateral and moments. Often these loads will act together to form a combination of loads, such as oblique forces that have a component of axial and lateral forces. Due to the pile’s length, which can extend past 30 m, it is difficult and expensive to carry out full scale testing. Any full-scale test data is limited to the area conditions and soil properties at the testing site. Small scale testing can be used as an alternative to full scale testing, although scaling effects will influence the conclusions from this type of study greatly. Computer simulations of finite element modelling allow for in- depth studies into the complex pile-soil interaction under combination loading in deep foundation structures. This work used 3D finite element modelling to explore the effect of pile shape, sand properties, pile length and loading conditions on the capacity of a pile. Using trends discovered by these simulations design charts were developed to aid consultants when determining the bearing capacity for oblique interaction for square piles. It was found through a carefully planned sensitivity analysis that sand properties and pile shape can influence the capacity of a pile extensively. The mesh density, boundary and initial stress conditions imposed on the simulation will ultimately determine the accuracy and reliability of the model results. To gain a good understanding of a model’s capability and accuracy the simulation output must be tested and verified against case studies. The trends obtained from modelling the complex mechanisms such as the pile-soil interaction allows for greater understanding of failure mechanisms, which could otherwise not be observed

Modelling the load-deformation response of deep foundations under oblique loading

Deep foundations are slender pile elements used to transfer loads from structures into deeper soil strata below the ground. Deep foundations have a variety of loads including axial, lateral and moment loads. Often these loads will act together to form a combination of loads, such as previous oblique term forces that have a component of axial and lateral forces. Due to the pile's length, which can extend past 30 m, it is difficult and expensive to carry out full-scale testing. Any full-scale test data are limited to the area conditions and soil properties at the testing site. Small scale testing can be used as an alternative to full-scale testing, although scaling effects will influence the conclusions from this type of study greatly. Computer simulations of finite element modelling allow for in-depth studies into the complex pile–soil interaction under combination loading in deep foundation structures. This work used three-dimensional finite element modelling using ABAQUS to explore the effect of pile shape, sand properties, pile length and loading conditions on the capacity of a pile. Using trends discovered by these simulations design charts were developed to aid designers when determining the bearing capacity for previous oblique term interaction for square piles. The final design chart shows the change in capacity for in-plane loaded, square cross-sectioned piles as compared to circular piles. The difference in capacity is shown to be a function of the previous oblique term interaction angle and length to diameter ratio