Mesures d’impédances pour l’optimisation de la sélectivité spatiale de la stimulation électrique par l’implant cochléaire

National audienc

Impedance measures for subject-specific optimization of spatial selectivity

International audienc

Sensibilité à la polarité de la stimulation chez l’implanté cochléaire : un indicateur de dégénérescence neuronale ?

National audienceLes sujets implantés cochléaires montrent une forte variabilité inter-individuelle dans diverses tâches perceptives. Ces différences sont souvent attribuées à des différences de dégénérescence entre les populations de neurones stimulés par les électrodes. Cependant, il n’existe actuellement aucun moyen objectif pour déterminer l’étendue de cette dégénérescence chez un sujet donné. Cette étude a pour but de tester si la sensibilité à la polarité de la stimulation, qui a été proposée comme un corrélat perceptif de la dégénérescence neuronale, est corrélée à la performance des sujets. 16 sujets implantés ont participé à l’expérience 1. Nous avons mesuré les seuils d’audibilité sur chacune de leurs électrodes pour des impulsions triphasiques à phase dominante positive ou négative. La sensibilité à la polarité, définie comme la différence entre les seuils obtenus pour des impulsions négative et positive, a montré des variations allant de -4 à +4 dB suivant les sujets et les électrodes. De plus, nous avons observé que la sensibilité à la polarité moyennée entre toutes les électrodes de chaque sujet était corrélée négativement avec leur performance sur une tâche de résolution spectrale. Ce résultat est cohérent avec l’hypothèse que des seuils relativement bas pour des impulsions négatives reflètent une population de neurones en bon état et donc une meilleure résolution spectrale. Nous présenterons les résultats d’une deuxième expérience allant également dans ce sens. Pour conclure, ces études suggèrent que la sensibilité à la polarité reflète en partie le degré de dégénérescence neuronale et que cette mesure pourrait être utilisée comme un guide pour sélectionner les meilleures électrodes à stimuler chez chaque patient

Refining the audiological assessment in children using narrow-band CE-Chirp-evoked auditory steady state responses

International audienceOBJECTIVE:To demonstrate the feasibility and reliability of simultaneous binaural recording of auditory steady-state responses (ASSR) in young children using narrow-band CE-Chirps as stimuli.DESIGN:Prospective cohort study comparing ASSR thresholds to four frequency stimuli (0.5, 1, 2, and 4 kHz), with click-evoked auditory brainstem responses (ABR) and behavioral response audiometry.STUDY SAMPLE:Thirty-two young children (mean age 7.4 ± 5.2 months) referred for auditory assessment were evaluated.RESULTS:The mean duration for ABR recordings was 13.3 ± 7.2 min versus 22.9 ± 15.8 min for ASSR (p < 0.01). ASSR (means of 2 and 4 kHz thresholds) were highly correlated with ABR thresholds (R2 = 0.935, p < 0.001), though significantly different (3 ± 10.7 dB, p = 0.02). ASSR (means of 0.5, 1, 2, and 4 kHz thresholds) were highly correlated with mean behavioral response audiometry thresholds (R2 = 0.968, p < 0.001). ASSRs were highly and significantly correlated with behavioral response audiometry at 0.5, 1, 2, and 4 kHz (R2 = 0.845, 0.907, 0.929, and 0.859 respectively, p < 0.001). 87.5% and 90.7% ASSR thresholds were within a ± 10 dB range around their corresponding ABR and mean behavioral response audiometry thresholds.CONCLUSIONS:Narrow-band CE-Chirps allow a fast and reliable assessment of auditory thresholds in children, especially in the low-frequency range, by comparison with other stimuli

Audiological Outcomes and Associated Factors after Pediatric Cochlear Reimplantation

Cochlear implants are the most common and successful sensory neuroprosthetic devices. However, reimplantation can be required for medical reasons, device failure, or technological upgrading. Resolving the problem driving the intervention and offering stable or better audiological results are the main challenges. We aimed to analyze the success rate of this intervention and to identify factors influencing speech perception recovery after reimplantation in the pediatric population. We retrospectively collected the causes and the outcomes of 67 consecutive reimplantations in one cochlear implant center over 30 years. Reimplantation resolved the cause without recurrence for 94% of patients. The etiology of deafness, time since implantation, indication of reimplantation, sex, and age did not influence word discrimination test scores in silence, 3 years after surgery. However, adherence to a speech rehabilitation program was statistically associated with gain in perception scores: +8.9% [&minus;2.2; +31.0%] versus &minus;19.0% [&minus;47.5; &minus;7.6%] if no or suboptimal rehabilitation was followed (p = 0.0037). Cochlear reimplantation in children is efficient and is associated with predictable improvement in speech perception, 3 years after intervention. However, good adherence to speech rehabilitation program is necessary and should be discussed with the patient and parents, especially for the indication of reimplantation for technological upgrading

HFUS Imaging of the Cochlea: A Feasibility Study for Anatomical Identification by Registration with MicroCT

International audienceCochlear implantation consists in electrically stimulating the auditory nerve by inserting an electrode array inside the cochlea, a bony structure of the inner ear. In the absence of any visual feedback, the insertion results in many cases of damages of the internal structures. This paper presents a feasibility study on intraoperative imaging and identification of cochlear structures with high-frequency ultrasound (HFUS). 6 ex-vivo guinea pig cochleae were subjected to both US and microcomputed tomography (µCT) we respectively referred as intraoperative and preoperative modalities. For each sample, registration based on simulating US from the scanner was performed to allow a precise matching between the visible structures. According to two otologists, the procedure led to a Target Registration Error (TRE) of 0.32 mm ± 0.05. Thanks to referring to a better preoperative anatomical representation, we were able to intraoperatively identify the modiolus, both scalae vestibuli and tympani and deduce the location of the basilar membrane, all of which is of great interest for cochlear implantation. Our main objective is to extend this procedure to the human case and thus provide a new tool for inner ear surgery

Medium-term assessment of Eustachian tube function after balloon dilation

International audienceThere is at present no consensus on the treatment of obstructive Eustachian tube dysfunction. In case of failure of well-conducted drug and pressure therapy, some authors recommend balloon dilation; the present study aimed to assess the efficacy and safety of Eustachian tube balloon dilation

Safety, tolerability, pharmacokinetics and pharmacokinetic-pharmacodynamic modelling of the novel H 4 receptor inhibitor SENS-111 using a modified caloric test in healthy subjects

International audienceAIM:A Phase 1 study was performed to evaluate safety, pharmacokinetics (PK) and pharmacodynamics (PD) of the selective histamine H4 receptor antagonist SENS-111, an oral small molecule.METHODS:One hundred healthy subjects were randomized in a placebo-controlled, double-blind study evaluating single-ascending doses (SAD; 100-500 mg) and multiple-ascending doses (MAD; 50-150 mg day-1 , 4 days; 200-250 mg day-1 , 7 days). Effects of SENS-111 on nystagmus and vertigo induced by modified caloric tests were measured in the MAD studies. Population PK and PK/PD models were developed using a nonlinear mixed-effects approach.RESULTS:SENS-111 was well tolerated with mild to moderate events. No sedation was reported. A maximal tolerated dose was not reached. Dose-proportional increases in concentrations were seen up to 200 mg and more than dose-proportional thereafter, with mean half-life between 24 and 56 h. The caloric test induced mild but measurable vertigo and nystagmus with large intra/inter-individual variation for all parameters. SENS-111 did not significantly impact nystagmus but significantly improved latency of vertigo appearance/disappearance, duration and European Evaluation of Vertigo questionnaire parameters vs. baseline. A two-compartment model with first-order absorption, distribution and elimination best fit the data. PK/PD indirect modelling applied to vertigo duration and latency of appearance indicated maximum activity between 100 and 500 ng ml-1 plasma concentrations, corresponding to 100 and 200 mg day-1 , which are appropriate for clinical efficacy evaluations in vestibular diseases.CONCLUSIONS:SENS-111 is a well-tolerated first-in-class H4 receptor antagonist with acceptable PK for oral daily dosing. PK/PD modelling determined plasma concentrations and doses for efficacy studies in patients with vertigo symptoms

Miniaturized endoscopic 2D US transducer for volumetric ultrasound imaging of the auditory system

International audienceIn this paper, we focus on the carrying out and validation of minimally invasive three-dimensional (3D) ultrasound (US) imaging of the auditory system, which is based on a new miniaturized endoscopic 2D US transducer. This unique probe consists of a 18 MHz 24 elements curved array transducer with a distal diameter of 4 mm so it can be inserted into the external auditory canal. Typical acquisition is achieved by rotating such a transducer around its own axis using a robotic platform. Reconstruction of a US volume from the set of acquired B-scans during the rotation is then performed using scan-conversion. The accuracy of the reconstruction procedure is evaluated using a dedicated phantom that includes a set of wires as reference geometry. Twelve acquisitions obtained from different probe poses are compared to a micro-computed tomographic model of the phantom, leading to a maximum error of 0.20 mm. Additionally, acquisitions with a cadaveric head highlight the clinical applicability of this set up. Structures of the auditory system such as the ossicles and the round window can be identified from the obtained 3D volumes. These results confirm that our technique enables the accurate imaging of the middle and inner ears without having to deteriorate the surrounding bone. Since US is a real-time, wide available and non-ionizing imaging modality, our acquisition setup could facilitate the minimally invasive diagnosis and surgical navigation for otology in a fast, costeffective and safe way

New perspectives for middle ear implants: first results in otosclerosis with mixed hearing loss.

International audienceMiddle ear implantation is an efficient procedure to restore moderate to severe sensorineural hearing loss (HL) in selected patients. Implantation of such devices requires ossicular chain integrity. Patients suffering from otosclerosis with mixed HL should be eligible for this treatment after stapes surgery with air-bone gap closure. To address this issue, we report four cases of middle ear implantation after or during stapes surgery. Results and complications obtained with Vibrant SoundBridge, MedEl and Middle Ear Transducer, Otologics are reported. Audiologic results were similar to those obtained in cases of sensorineural HL. One case of postoperative labyrinthitis was observed