Endolymphatic hydrops is defined as an accumulation of endolymph in the inner ear leading to a buildup of pressure and distortion of intralabyrinthine structures. The pressure variation is neither obvious nor easy to measure and remains not clearly confirmed. The distortion of endolymphatic structures has been the main described phenomenon since Hallpike, Cairns and Yamakawa in 1938. However, some clinical symptoms associated with endolymphatic hydrops are in addition to the typical triad of symptoms of Meniere's disease. This introduction to the state of the art is an analysis of the relationship between hydrops and clinical vestibular disorders, with a focus on the dynamics of endolymphatic hydrops. The distortion of endolabyrinthine structures can be considered as a dynamic process modeled with mechanical elastic behavior.

INTRODUCTION:According to the literature and our recent experience, even if patients present with symptoms strongly suggestive of benign paroxysmal positional vertigo (BPPV), the observed positional nystagmus does not always correspond to any previously described typical location. The aim of this multicentric study was to evaluate the frequency of both typical and less common forms of BPPV.MATERIAL AND METHODS:All consecutive patients presenting with BPPV in two hospitals between November 2016 and October 2017 were included. For each subject, answers to a standardized evaluation form and a recorded videonystagmoscopy were obtained by two otorhinolaryngologists. Appropriate diagnostic and therapeutic maneuvers were performed.RESULTS:A total of 532 patients were studied and 491 cases of typical BPPV were found: 370 cases of canalolithiasis of the posterior semicircular canal (SCC), 3 cases of canalolithiasis of the anterior SCC, 107 cases of canalolithiasis of the lateral SCC, and 11 cases of cupulolithiasis of the lateral SCC. Fourty one patients reported symptoms suggestive of BPPV with positional nystagmus that could correspond to unusual locations of otoconia in the SCC: 18 cases of canalolithiasis in the anterior ampulla of the lateral SCC, 16 cases of posterior short arm canalolithiasis, four cases of pseudo-spontaneous nystagmus in canalolithiasis of the lateral SCC, and three cases of canalolithiasis of the posterior third of SCC.DISCUSSION:Unusual BPPV accounted for almost 8% of BPPV treated in our clinics; it is paramount to know how to diagnose them, to carry out the appropriate therapeutic maneuvers and relieve these patients.

The human inner ear hosts a fundamental component of the mechanisms regulating balance and maintaining gaze: the vestibular system. It can detect motion thanks to three semicircular canals (SCC), w...

Objective: The aim of this work is to create a three-dimensional (3D) finite element model (FEM) of the human posterior membranous labyrinth, based on in vivo inner ear magnetic resonance imaging (MRI). Study design and setting:We used T2 weighted gradient-echo 3T MRI of a human inner ear.Images were acquired in vivo, from a patient presenting a vestibular schwannoma with a preserved labyrinthine geometry.Indeed, in this context, the elevation of the perilymphatic protides level secondary to the obstructive vestibular schwannoma enables a differentiation between the endolymph (which remains hyperintense on T2 weighted images) and the perilymph (hypointense on T2 weighted gradient echo images).Results: A 3D reconstruction of the posterior membranous labyrinth was performed through manual segmentation of the endolymphatic and sensory spaces.A mesh of the labyrinth was realized, first of its outer surface and then of its interior volume.The different structures of the labyrinth are included through a compartmentalization of the mesh.Sensory zones are precisely defined, based on a radio-histological correlation study.The resulting mesh of the model included 124,701 elements. Conclusion:Dimensions are in agreement with those in the literature, which is in favor of the validity of the model geometry.This model also has a pedagogical interest and can be useful for the clinical reflexion in cases of atypical benign paroxysmal positional vertigos (BPPV).It can also serve as a base for mechanical studies of vestibular physiology. Key points1.This 3D model is based on in vivo inner ear imaging.2. It is a FEM of human posterior membranous labyrinth.3. This model includes all the sensory zones of the posterior membranous labyrinth.

The objective of this study was to develop a visco-hyperelastic constitutive law for the FE modeling of brain tissue. Material properties of a visco-hyperelastic constitutive model were determined via the application of FE simulations and optimization methodology. Basic FE models were developed according to referred dynamic uniaxial tension tests of brain tissue with uniform strain rates of 30 s-1 and 90 s-1 up to 30% strain. The optimization objective was to minimize fitting errors between strain-stress curves predicted by FE simulations and corresponding curves measured from referred experiments. Material constants of a visco-hyperelastic constitutive model was defined as constant or design parameters for the optimization procedure, with given values or design domain. Uniform Latin Hypercube algorithm was applied to generate the initial group of FE models, and an improved multi-objective genetic algorithm (MOGA-II) was applied as the optimization strategy. Results indicates that the strain-stress curves predicted by the optimized FE models were located in experimental corridors when the strain higher than 15% for both strain rates of 30 s-1 and 90 s-1. Thus, the proposed visco-hyperelastic constitutive law could be applied in FEHMs for the prediction of intracranial mechanical responses at injury levels.

The purpose of this study is to investigate the brain-strain-based thresholds for better prediction of the diffuse axonal injury (DAI) induced by a rotational acceleration on the rat brain. A previously developed and validated rat head finite element model was used to reconstruct 26 in vivo rat head impact experiments. DAI was produced via the high rotational acceleration applied to the rat head on the sagittal plane. Intracranial strain and strain-based injury indexes were calculated, including the maximum principal strain (MPS), the product of strain and strain rate, and the cumulative strain damage measure (CSDM). The region-specific conservative thresholds for DAI were estimated in terms of strain and strain-based injury indexes in the frontal, middle, and occipital regions of the corpus callosum. The axonal injuries observed in the experiments were used to formulate the injury risk functions, and the DAI risks were analysed via binary logistic regressions in terms of the calculated injury indexes. The logistic regression analysis demonstrated that the MPS, the product of strain and strain rate, as well as the CSDM were significantly correlated with DAI in the frontal corpus callosum. For the 50% probability of DAI in the frontal corpus callosum, it is suggested that the strain-based threshold is 0.12 for the MPS, 110 s(-1) for the product of strain and strain rate, and 17% for the CSDM.

Entrepreneurship and innovation processes are important dynamics that shape the development of peripheral regions. Regional policy increasingly takes these dynamics into account when trying to foster development in non-core regions. This paper provides the foundation for understanding the role of entrepreneurship in peripheral regions. We first review general characteristics of so-called peripheral regions and their implications for fostering entrepreneurship and innovation. We then investigate the state of research on these dynamics in the context of Switzerland. Finally, we present an overview of the central findings of the papers in this special issue.

Les deux Chambres ayant accepte la motion Maissen (11.3927) intitulee « Strategie de la Confederation pour les regions de montagne et les espaces ruraux », le Conseil federal est charge d’elaborer une strategie coherente de developpement des regions de montagne et des espaces ruraux de la Suisse. L'elaboration de cette strategie a ete confiee au Secretariat d'Etat a l'economie (SECO), qui a mis sur pied un groupe tripartite et a prepare, suite a sept ateliers realise en collaboration avec un groupe d'experts de l’UNIGE et UNIBE, un rapport ad hoc. Ce rapport formule les objectifs strategiques a atteindre et l'orientation a donner aux activites de la Confederation en ce qui concerne les regions de montagne et les espaces ruraux.

Traumatic head injuries can result from vehicular accidents, sports, falls or assaults. The current advances in computational methods and the detailed finite element models of the human head provide a significant opportunity for biomechanical study of human head injuries. The biomechanical characteristics of the human head through head impact scenarios can be studied in detail by using the finite element models. Skull fracture is one of the most frequent occurring types of head injuries. The purpose of this study is to analyse the experimental head impacts on cadavers by means of the Strasbourg University Finite Element Head Model (SUFEHM). The results of the numerical model and experimental data are compared for validation purpose. The finite element model has also been applied to predict the skull bone fracture in frontal impacts. The head model includes the scalp, the facial bone, the skull, the cerebral spinal fluid, the meninges, the cerebrum and the cerebellum. The model is used to simulate the experimental frontal head impact tests using a cylindrical padded impactor. Results of the computational simulation shows that the model correlated well with a number of experimental data and a global fracture pattern has been predicted well by the model. Therefore the presented numerical model could be used for reconstruction of head impacts in different impact conditions also the forensic application of the head model would provide a tool for investigation of the causes and mechanism of head injuries.