Acoustic transfer using an active middle ear implant : effect on performance of the coupling to the middle ear

La surdité est un problème de santé publique. Le vieillissement de la population explique ainsi une grande partie des causes de surdités, par la fréquence de la presbyacousie. Le principal moyen de la réhabilitation auditive est représenté par les prothèses auditives conventionnelles. Les aides auditives ont considérablement progressé ces dernières années, principalement en termes d’amélioration du traitement du signal. Ceci étant dit, outre le problème économique, certains facteurs limitent encore les bénéfices que les patients peuvent ressentir (occlusion du conduit auditif, effet larsen, absence d’amplification en ambiance sonore,…). Les implants d’oreille moyenne sont destinés à amplifier le signal sonore en le transmettant à l’oreille moyenne pour compenser une perte auditive. Ils sont indiqués en cas d’échec ou de contre-indication de l’appareillage conventionnel. Cependant, les implants d’oreille moyenne présentent certaines limites comme l’insuffisance de performance. Des données récentes montrent que les performances des techniques de réparation de la chaîne ossiculaire sont dépendantes du couplage des prothèses ossiculaires à la chaîne des osselets. Par ailleurs, des avancées dans la compréhension de la biomécanique de la chaîne ossiculaire confirment l’importance du placement et du couplage des procédés de restauration chirurgicaux. Nous avons formulé l’hypothèse selon laquelle ces données pouvaient être appliquées aux implants d’oreille moyenne pour en améliorer les performances. Nous avons voulu analyser expérimentalement les effets sur les performances de variables telles que : placement d’un transducteur, le couplage à la chaîne des osselets, la taille de l’effecteur, l’effet de stimulations alternatives. Nous avons utilisé un transducteur électromagnétique de dernière génération (Otologics MET-V Gen 2) et une technique d’analyse de la vibration des structures de l’oreille moyenne par vélocimétrie laser. Les résultats ont montré une nette amélioration des performances en fonction des modifications de placement et de couplage à la chaîne des osselets ou à la fenêtre ronde.Hearing loss is a public health issue. Ageing is the most frequent cause of deafness. The main option for the rehabilitation of hearing loss is the use of conventional hearing aids. These aids have dramatically improved their performance for the past 20 years, mostly with regards to signal processing. However, in addition to economic reasons, some limitations remain (occlusion, feedback, hearing in noise…) and limit the satisfaction of patients. Active middle ear implants (AMEI) have been developed to overcome some of these problems and are indicated n conventional hearing failed to improve patients’ quality of hearing. However, AMEI suffer from limitations, as insufficient performances for severe hearing losses. Recent experimental and clinical data have highlighted the importance of coupling and placement of ossicular reconstruction passive prosthesis use. Other reported new findings regarding the biomechanism of the ossicular chain, especially for high frequency hearing, which is, unfortunately, where most people have their hearing loss. We hypothesized that these findings could be applied to AMEI use. We have analysed experimentally the effects on AMEI performance of variables such as: placement, coupling, size of tranduscer vibrating tip, alternative stimulation options. We used a electromagnetic tranducer from Otologics LLC to drive the middle ear or round window membrane, and a laser Doppler vibrometer to assess for the induced middle transfer function. Results have shown that we could provide great improvement in performance when varying the coupling method and the placement to the ossicular chain or the round window membrane

Contraction of the stapedius and tensor tympani muscles explored by tympanometry and pressure measurement in the external auditory canal

International audienc

Where is straight ahead to a patient with unilateral vestibular loss?

The vestibular system is classically associated with postural control, oculomotor reflexes and self-motion perception. The patients with vestibular loss are primarily concerned with balance and gait problems including head and trunk tilt and walking trajectory deviation to the lesioned side. These long-lasting postural and locomotor biases are thought to originate from changes in spatial perception of self. Indeed, we show here that vestibular cues are necessary for an accurate representation of body orientation. Patients with right (RVN; n=11) or left vestibular neurotomy (LVN; 9) as a treatment for Menière's disease were compared with 10 healthy controls. The subjective straight ahead (SSA) was investigated using a method disentangling lateral shift and tilt components of error. In the horizontal plane, subjects were required to align a rod with their body midline. In the frontal plane, they were asked to align the rod with the midline of head or trunk. The analysis of SSA clearly showed distinct results according to the side of the lesion. The LVN patients had a contralesional lateral shift of SSA. In addition, they showed an ipsilesional tilt, more severe for the head than for the trunk. By contrast, in RVN patients, the representation of the body midline was fairly accurate in both the horizontal and frontal planes and did not differ from that of control subjects. The present study shows deviations in body orientation representation after unilateral vestibular loss. Deviations are observed in the horizontal as well as in the frontal planes. Interestingly, only patients with left vestibular loss were concerned with these changes in perception of self-orientation in space. These data support the hypothesis of an asymmetric vestibular function in healthy subjects and confirm the similarity of functional disorders in patients with vestibular deficits or spatial neglect. For the first time, this similarity is found at the level of body representation

Unilateral vestibular loss impairs external space representation.

The vestibular system is responsible for a wide range of postural and oculomotor functions and maintains an internal, updated representation of the position and movement of the head in space. In this study, we assessed whether unilateral vestibular loss affects external space representation. Patients with Menière's disease and healthy participants were instructed to point to memorized targets in near (peripersonal) and far (extrapersonal) spaces in the absence or presence of a visual background. These individuals were also required to estimate their body pointing direction. Menière's disease patients were tested before unilateral vestibular neurotomy and during the recovery period (one week and one month after the operation), and healthy participants were tested at similar times. Unilateral vestibular loss impaired the representation of both the external space and the body pointing direction: in the dark, the configuration of perceived targets was shifted toward the lesioned side and compressed toward the contralesioned hemifield, with higher pointing error in the near space. Performance varied according to the time elapsed after neurotomy: deficits were stronger during the early stages, while gradual compensation occurred subsequently. These findings provide the first demonstration of the critical role of vestibular signals in the representation of external space and of body pointing direction in the early stages after unilateral vestibular loss

Genome-wide analysis of familial dysautonomia and kinetin target genes with patient olfactory ecto-mesenchymal stem cells.

International audienceFamilial dysautonomia (FD) is a rare inherited neurodegenerative disorder. The most common mutation is a c.2204+6T>C transition in the 5' splice site (5'ss) of IKBKAP intron 20, which causes a tissue-specific skipping of exon 20, resulting in lower synthesis of IKAP/hELP1 protein. To better understand the specificity of neuron loss in FD, we modeled the molecular mechanisms of IKBKAP mRNA splicing by studying human olfactory ecto-mesenchymal stem cells (hOE-MSCs) derived from FD patient nasal biopsies. We explored how the modulation of IKBKAP mRNA alternative splicing impacts the transcriptome at the genome-wide level. We found that the FD transcriptional signature was highly associated with biological functions related to the development of the nervous system. In addition, we identified target genes of kinetin, a plant cytokinin that corrects IKBKAP mRNA splicing and increases the expression of IKAP/hELP1. We identified this compound as a putative regulator of splicing factors and added new evidence for a sequence-specific correction of splicing. In conclusion, hOE-MSCs isolated from FD patients represent a promising avenue for modeling the altered genetic expression of FD, demonstrating a methodology that can be applied to a host of other genetic disorders to test the therapeutic potential of candidate molecules

Vestibular information is necessary for maintaining metric properties of representational space: evidence from mental imagery

International audienceThe vestibular system contributes to a wide range of functions, from postural and oculomotor reflexes to spatial representation and cognition. Vestibular signals are important to maintain an internal, updated representation of the body position and movement in space. However, it is not clear to what extent they are also necessary to mentally simulate movement in situations that do not involve displacements of the body, as in mental imagery. The present study assessed how vestibular loss can affect object-based mental transformations (OMTs), i.e., imagined rotations or translations of objects relative to the environment. Participants performed one task of mental rotation of 3D-objects and two mental scanning tasks dealing with the ability to build and manipulate mental images that have metric properties. Meniere's disease patients were tested before unilateral vestibular neurotomy and during the recovery period (1 week and 1 month). They were compared to healthy participants tested at similar time intervals and to bilateral vestibular-defective patients tested after the recovery period. Vestibular loss impaired all mental imagery tasks. Performance varied according to the extent of vestibular loss (bilateral patients were frequently the most impaired) and according to the time elapsed after unilateral vestibular neurotomy (deficits were stronger at the early stage after neurotomy and then gradually compensated). These findings indicate that vestibular signals are necessary to perform OMTs and provide the first demonstration of the critical role of vestibular signals in processing metric properties of mental representations. They suggest that vestibular loss disorganizes brain structures commonly involved in mental imagery, and more generally in mental representation. (C) 2011 Elsevier Ltd. All rights reserved

Effect of unilateral vestibular loss on the visual straight-ahead (SSA) as a function of session.

<p>Mean (±95% CI).</p

Schematic representation of the experimental setup for the pointing tasks: sagittal view (top) and top-view (bottom).

<p>The participant was seated in front of the three spaces on which red dots were projected as target stimuli. When the target disappeared, the participant moved the laser pointer to the memorized location. From the observer's position, the horizontal near and far spaces correspond to a viewing angle of approximately 40×24 degrees and 35×12 degrees in the horizontal plane, respectively. The vertical space corresponds to a viewing angle of approximately 26×19 degrees in the vertical plane. At bottom, the top-view shows the two concentric rectangles and the angular distribution of the targets in the near and far spaces. In the experiment, the rectangles are formed with white stripes on a black backdrop and are visible only in the light condition.</p

Average pointing error (degrees) for each target in the near and far spaces for each group of participants.

<p>Three sessions were plotted for the patients, while only the average values were plotted for the controls because their variations across sessions were non-significant. Mean (±95% confidence intervals).</p