Visual-vestibular compensation in balance recovery: A transfer function model-based analysis

International audienc

Stimulations des voies auditives : nouveaux procédés

I started my research by investigating the efficiency of a new method of brainstem auditory evoked potentials (BAEPs) monitoring during complete vestibular schwannoma resection with attempted hearing preservation. Auditory monitoring alerts the surgeon to ongoing changes in neural function, but the existing techniques have their limitations, suggesting the application of new methods. Combined BAEPs and direct auditory nerve monitoring will be performed in the future in attempt to enhance the chances of preventing irreversible hearing damage, and possibly improve the hearing outcome significantly. To achieve this goal, a multipoint flexible surface microelectrode for direct cortical recordings with a high spatiotemporal resolution has been fabricated and tested in animals. Recordings of cortical activities elicited by both acoustic and electrical stimulation on the cochlear nucleus have focused on the feasibility. Such electrodes are expected to enhance auditory neural coding understanding and provide new developments in human auditory monitoring and hearing rehabilitation, such as auditory brainstem implant (ABI). Access to the tonotopic organization of the cochlear nucleus with the existing ABI is limited. We have focused on basic prosperities, functional stimulation criteria in the auditory system, precise micro-stimulation, safety and efficacy of in-depth electrical stimulation of the cochlear nucleus using rat model. With collaboration with bioengineering department we have designed flexible multi-channel surface electrode that enables simultaneously recording from 64 different points on the surface of the auditory cortex after stimulating auditory periphery by sound or electrical stimuli with high spatial resolution. Using multi-channel electrode in vivo experiments revealed clearly differentiated evoked potentials in a spatio-temporal maps on the auditory cortex which varies by changing acoustic stimuli representing particular neuronal processing over the recording area. We have investigated whether sound and electrical stimulation has same physiological bases in the cochlear nucleus, inferior colliculus, and auditory cortex. We hope with this approach be able to examine long-term safety of implantation at the brainstem and effect of electrical stimulation on the other neuronal pathway at brainstem. Beside the basic research on this topic, I have also engaged in other research activities related to hearing and auditory system. We are trying to achieve a better understanding of the hearing performances in aural atresia patients. This topic has been studied in the ENT department of the University of Tokyo through electrophysiogical studies, using auditory brainstem evoked potentials and binaural interaction components in animals and in human, vestibular evoked myogenic potentials (acoustic and bone conducted stimuli). Behavioral studies were also conducted using bilateral bone-conducted stimuli paradigm. Our results suggest that the mature auditory brainstem has a plasticity potential to employ binaural cues later in life in patients who had an abnormal hearing experience.J'ai débuté ma recherche par l'étude d'une nouvelle méthode de monitoring auditif per-opératoire par potentiels évoqués auditifs durant la chirurgie des schwannomes vestibulaires avec tentative de préservation de l'audition. L'utilisation de techniques combinées avec enregistrement de potentiels directs de nerf est en cours de développement dans l'espoir d'améliorer les chances de préservation auditive. Les potentiels directs de nerf reposent notamment sur des technologies microélectrodes souples que j'ai testées sur modèle animal. Des enregistrements du cortex auditif obtenus par stimulation acoustique et électrique dans le noyau cochléaire ont démontré la faisabilité de l'enregistrement par microélectrode souple sur support poliimide. J'ai ainsi pu mener en collaboration avec l'Université de Tokyo un programme de recherche sur un nouveau type d'implant du tronc cérébral par électrode de stimulation profonde, qui permet un meilleur accès à la représentation tonotopique du noyau cochléaire. Les réponses électrophysiologiques ont été obtenues par technique de mapping de surfaces corticales avec des microélectrodes souples à haute résolution spatiale (64 sites), développées en collaboration avec le département d'ingénierie de l'Université de Tokyo. Nous avons montré qu'il est possible d'accéder à la tonotopie du noyau cochléaire par stimulation électrique profonde. Des études complémentaires de tolérance et d'efficacité, notamment au cours d'implantation chronique sont cependant indispensables. J'ai également participé à un travail de recherche clinique sur l'audition et le vestibule sur des patients ayant des atrésies aurales. L'étude de ces patients par méthode électrophysiologique (PEA bilatéraux et étude des composants d'interaction binaurale, potentiels évoqués saculo-colliques myogènes), comportementale (étude des facteurs de localisation, en particulier le facteur de compensation temps/intensité) est une approche originale de la plasticité cérébrale existante chez les patients ayant vécus des expériences auditives anormale

Accuracy evaluation of a CAS system: laboratory protocol and results with 6D localizers, and clinical experiences in otorhinolaryngology

OBJECTIVES: The objective of the study reported in this article was to evaluate (1) localizer inaccuracies, one of the major sources of errors in Computer-Assisted Surgery (CAS) systems, and (2) the final errors obtained using surface-based registration in ear, nose, and throat (ENT) surgery. These objectives were met through (1) a technical evaluation of the accuracy and usability of several optical localizers under laboratory test conditions, and (2) a clinical measure of the global errors obtained when using a CAS system including one of the standard localizer systems (Flashpoint 5000) in Functional Endoscopic Sinus Surgery (FESS). PATIENTS AND METHODS: The technical evaluation of localizers consisted of series of geometric tests on four commercial systems. Clinical evaluation included the development of a laboratory CAS system using a markerless, skin surface registration method. This was based on a standard optical digitizing system (Flashpoint 5000), which eliminates the need for the second CT scan, which is normally performed specifically to process the position of the fiducial markers. Global accuracy was then evaluated on 20 patients by subjective and visual comparison when placing a calibrated pointer on anatomical landmarks. RESULTS: The results of the technical study indicate that the four commercial systems tested have levels of inaccuracy deemed acceptable for most CAS applications, including ENT surgery. The clinical study obtained a registration and calibration accuracy of less than 1.5 mm in 89.2% (SD = 0.20 mm) of the cases studied. Our markerless skin surface points registration method is reliable, and allows patient head movements during the procedure. The accuracy tests performed show that this type of system can be used for ENT surgery with satisfaction. CONCLUSION: CAS systems enable the surgeon to have a more thorough understanding of the complicated anatomy of paranasal sinuses, and may be especially helpful in revision surgery when normal anatomic landmarks are lacking. Further studies are necessary in FESS to improve the CAS systems that are currently available, and to determine whether these systems can minimize the overall risk of complications

Is child speech intelligible? The case of cochlear implanted (CI) vs normal-hearing (NH) children

International audienc

Vein versus tragal perichondrium in stapedotomy

OBJECTIVE: To assess, in otosclerosis surgery, whether the vein or the tragal perichondrium in stapedotomy with interposition yields the better long-term hearing outcome. STUDY DESIGN: A retrospective chart review of prospectively collected audiometric data of 452 ears. SETTING: Academic tertiary otology-neurotology referral center. PATIENTS: Four hundred fifty-two stapedotomies with interposition were performed in 412 patients (bilateral in 40 patients) by the senior author (R.C.) between 1987 and 1998. A tragal perichondrium graft was used in 314 cases and a vein graft was used in 138 cases as sealing material of the oval window. MAIN OUTCOME MEASURES: Audiometric data were recorded at 4 months, at 1 year, and at 3 years after surgery after American Academy of Otolaryngology-Head and Neck Surgery guidelines, except for thresholds at 3 kHz, which were not available and which were replaced with those at 4 kHz. RESULTS: There were no significant intergroup differences in initial or late postoperative hearing outcome with regard to change in the pure-tone average bone conduction and air-bone gaps, or sensorineural hearing loss. Ears treated with a vein graft showed statistically better postoperative 2-kHz air-bone gap closure (p =0.0157), but the pure-tone average air-bone gap difference was not significant. Postoperative air-bone gap closure to within 10 dB was achieved in 91% of cases in the vein group and in 76% of cases in the perichondrium group. Specific study of the bone conduction level at 4 kHz showed a sensorineural hearing loss greater than 10 dB in 8% of cases in the vein group and in 11% of cases in the perichondrium group. One case of complete sensorineural hearing loss was observed with a tragal perichondrium graft (0.22%). CONCLUSION: These results suggest that the vein should be preferred to the tragal perichondrium in stapedotomy with interposition

Comment réaliser le test de vibration osseux vestibulaire (TVOV)

International audienceLe test de vibration osseux vestibulaire est un test robuste, de réalisation simple, non invasif, qui se comporte comme un test de Weber vestibulaire haute fréquence et permet au fauteuil de consultation de révéler instantanément une asymétrie vestibulaire même ancienne ou compensée sous la forme d’un nystagmus induit par les vibrations. Ce test se pratique chez un sujet assis en stimulant successivement la mastoïde droite puis gauche (en regard des conduits auditifs externes) puis le vertex à 30, 60, ou plus efficacement à 100 Hz. Il peut être observé sous vidéoscopie, lunettes de Frenzel ou enregistré en vidéonystagmographie 2D ou 3D en trace directe ou en enregistrement de la vitesse de phase lente chez un sujet présentant un état de relaxation suffisant et non traité par des sédatifs. Ce test rapide de premier niveau, non influencé par la compensation vestibulaire, complète utilement les autres explorations vestibulaires dans l’analyse multi-fréquentielle du vestibule et se comporte comme un test vestibulaire global interrogeant les structures canalaires et otolithiques. Il est également informatif si le test calorique à l’eau n’est pas possible (lésions d’oreille moyenne ou externe), et chez le sujet âgé arthrosique et vasculaire chez qui le Head-Shaking-Test et/ou le Head-Impulse-Test ne sont pas réalisables

Flexibility of sensorimotor integration in visual virtual immersion. Case of vestibular patients

International audienc

Immersive Virtual Environment for Visuo-Vestibular Therapy: Preliminary Results

International audienceThe sense of equilibrium aggregates several interacting cues. On patients with vestibular loss, vision plays a major role. In this study, the goal is to propose a new immersive therapy based on 3D opto-kinetic stimulation. We propose to demonstrate that 3D monoscopic optical flows are an efficient tool to stimulate adaptive postural adjustment. We developed an immersive therapeutic platform that enables to tune the balance task difficulty by managing optic flow speed and gaze anchoring. METHODOLOGY: the immersive sessions proposed to vestibular areflexic patients are composed of a repetition of dynamic optic flows, with varying speed and presence or not of a gaze anchor. The balance adjustments are recorded by a force plate, and quantified by the length of the center of pressure trajectory. RESULTS: Preliminary analysis shows that (i) Patients report a strong immersion felling in the motion flow, triggering more intense motor response to "fight against fall" than in standard opto-kinetic protocols; (ii) An ANOVA factorial design shows a significant effect of flow speed, session number and gaze anchor impact. CONCLUSION: This study shows that 3D immersive stimulation removes essential limits of traditional opto-kinetic stimulators (limited 2D motions and remaining fixed background cues). Moreover, the immersive optic flow stimulation is an efficient tool to induce balance adaptive reactions in vestibular patients. Hence, such a platform appears to be a powerful therapeutic tool for training and relearning of balance control processes

Flexibility of sensorimotor integration in visual virtual immersion. Case of vestibular patients

International audienc

Realisation of voicing by French-speaking CI children after long-term implant use: An acoustic study

International audienceStudies of speech production in French-speaking cochlear-implanted (CI) children are very scarce. Yet, difficulties in speech production have been shown to impact the intelligibility of these children. The goal of this study is to understand the effect of long-term use of cochlear implant on speech production, and more precisely on the coordination of laryngeal-oral gestures in stop production. The participants were all monolingual French children: 13 6;6- to 10;7-year-old CI children and 20 age-matched normally hearing (NH) children. We compared /p/, /t/, /k/, /b/, /d/ and /g/ in word-initial consonant-vowel sequences, produced in isolation in two different tasks, and we studied the effects of CI use, vowel context, task and age factors (i.e. chronological age, age at implantation and duration of implant use). Statistical analyses show a difference in voicing production between groups for voiceless consonants (shorter Voice Onset Times for CI children), with significance reached only for /k/, but no difference for voiced consonants. Our study indicates that in the long run, use of CI seems to have limited effects on the acquisition of oro-laryngeal coordination needed to produce voicing, except for specific difficulties located on velars. In a follow-up study, further acoustic analyses on vowel and fricative production by the same children reveal more difficulties, which suggest that cochlear implantation impacts frequency-based features (second formant of vowels and spectral moments of fricatives) more than durational cues (voicing)