Maria-Izabel Kos

Acoustic to Electric Pitch Comparisons in Cochlear Implant Subjects with Residual Hearing

The aim of this study was to assess the frequency–position function resulting from electric stimulation of electrodes in cochlear implant subjects with significant residual hearing in their nonimplanted ear. Six cochlear implant users compared the pitch of the auditory sensation produced by stimulation of an intracochlear electrode to the pitch of acoustic pure tones presented to their contralateral nonimplanted ear. Subjects were implanted with different Clarion® electrode arrays, designed to lie close to the inner wall of the cochlea. High-resolution radiographs were used to determine the electrode positions in the cochlea. Four out of six subjects presented electrode insertions deeper than 450°. We used a two-interval (one acoustic, one electric), two-alternative forced choice protocol (2I-2AFC), asking the subject to indicate which stimulus sounded the highest in pitch. Pure tones were used as acoustic stimuli. Electric stimuli consisted of trains of biphasic pulses presented at relatively high rates [higher than 700 pulses per second (pps)]. First, all electric stimuli were balanced in loudness across electrodes. Second, acoustic pure tones, chosen to approximate roughly the pitch sensation produced by each electrode, were balanced in loudness to electric stimuli. When electrode insertion lengths were used to describe electrode positions, the pitch sensations produced by electric stimulation were found to be more than two octaves lower than predicted by Greenwoods frequency–position function. When insertion angles were used to describe electrode positions, the pitch sensations were found about one octave lower than the frequency–position function of a normal ear. The difference found between both descriptions is because of the fact that these electrode arrays were designed to lie close to the modiolus. As a consequence, the site of excitation produced at the level of the organ of Corti corresponds to a longer length than the electrode insertion length, which is used in Greenwoods function. Although exact measurements of the round window position as well as the length of the cochlea could explain the remaining one octave difference found when insertion angles were used, physiological phenomena (e.g., stimulation of the spiral ganglion cells) could also create this difference. From these data, analysis filters could be determined in sound coding strategies to match the pitch percepts elicited by electrode stimulation. This step might be of main importance for music perception and for the fitting of bilateral cochlear implants.

Forward masking in different cochlear implant systems

The goal of this study was to evaluate, from a psychophysical standpoint, the neural spread of excitation produced by the stimulation of different types of intracochlear electrode arrays: the Ineraid, the Clarion S-Series on its own or with the Electrode Positioning System (EPS), and the Clarion HiFocus-I with the EPS. The EPS is an independent silicone part designed to bring the electrode array close to the modiolus. Forward masking was evaluated in 12 adult subjects (3 Ineraid, 4 Clarion S-Series, 3 Clarion S-Series+EPS, 3 HiFocus-I+EPS) by psychophysical experiments conducted using trains of biphasic stimuli (813 pulses per second, 307.6 micros/phase). Masker signals (+8 dB re: threshold, 300 ms) were applied to the most apical electrode. Probe signals (30 ms, 10-ms postmasker) were delivered to more basal electrodes. Masked and unmasked detection thresholds of probe signals were measured. For both Clarion HiFocus-I subjects, measurements were conducted in both monopolar and bipolar stimulus configurations. No major differences were found in forward masking between the different intracochlear electrode arrays tested in the monopolar configuration at suprathreshold levels equivalent to those used in speech-coding strategies, but significant differences were found between subjects. A significant negative correlation also was found between the level of forward masking and the consonant identification performance. These measurements showed that the neural spread of excitation was more restricted in the bipolar configuration than in the monopolar configuration for HiFocus-I subjects. It was found that CIS strategies implemented without using apical electrodes, which showed high levels of masking, could improve consonant identification.

Measurements of electrode position inside the cochlea for different cochlear implant systems

Conclusions This study demonstrates that the exact location of an electrode inside the cochlea needs to be assessed using two complementary measures, namely the length and angle of insertion, both of which are mandatory if one wants to prevent erroneous outcomes. Knowledge of the contact position may become very useful when tuning a cochlear implant processor in a patient with contralateral residual hearing, or in cases of binaural implants. Objective Multichannel cochlear implants restore useful hearing to deaf patients. However, several types of intracochlear electrodes are presently available, each featuring a specific technology or design. The aim of this study was to determine precisely the intracochlear position of the contacts for different electrode arrays. Material and methods Electrode array insertions were estimated using special radiographs. A total of 26 cochlear implantations were included in the study: 6 Ineraid™; 5 Clarion™ HiFocus I; 11 Clarion HiFocus II; and 4 Med-El™ Combi40+. In each case, a measurable reference or marker ring placed close to the round window (within 2 mm) could be identified. Insertion lengths and angles were measured and then plotted on a graph based on 3D reconstructions. Results Both Clarion HiFocus I and II electrode arrays were found to be placed close to the inner wall of the cochlea. Ineraid and Med-El Combi40+ electrode arrays were both placed close to the organ of Corti, the Med-El Combi40+ arrays demonstrating the deepest insertions overall. In spite of marked differences in the positions of the contacts, we did not find any correlation with speech perception performance for the different types of implants studied.

Consultation conjointe médico-psychologique pour les patients souffrant d’acouphènes

En 1993, une consultation conjointe médico-psychologique a été mise en place pour les patients souffrant d’acouphènes. Dans cette consultation, les problèmes des patients sont abordés de façon spécifique, le but de la consultation étant d’être thérapeutique en elle-même. Le principal travail est d’aider les patients à s’exprimer tant sur la gêne auditive que sur les autres dimensions qui sont venues modifier leur tolérance à l’acouphène. Les motivations des patients à consulter de nombreux spécialistes sont explorées et analysées. Il apparaît que les attentes de chaque consultation réactivent l’angoisse. Chez tous les patients une plainte affective s’exprime derrière la plainte ORL. La présence conjointe des deux thérapeutes, spécialiste ORL et psychologue, permet aux patients d’unifier leur compréhension du phénomène auditif et de la manière dont ils le vivent. A ce jour, 435 consultations conjointes ont été réalisées. Les résultats ont été analysés par une personne non impliquée dans cette consultation et sont publiés dans l’article suivant de E. Perrin et al.

Joint medico-psychological consultation for patients suffering from tinnitus.

Because no effective treatment against tinnitus is available, all sorts of approaches have been developed. We believe the care of tinnitus patients concerns mainly ENT medical doctors. In order to take care of such patients, we started in 1993 a joint medico-psychological consultation (JMPC) to dispense adequate care for patients and training to the ENT residents. Every patient visiting our clinic for a tinnitus consultation benefits first from a comprehensive audiological examination. Once all objective causes of tinnitus are excluded, those patients who were not able to accept their auditory disorder or who insist on focusing on the annoyance caused by the perception of their tinnitus are invited by the doctor to the JMPC. The intolerance caused by tinnitus is enhanced by psychological and social aspects. These aspects are considered and discussed during the JMPC. The patients talk about their tinnitus bringing additional information on professional, familial and relational issues. In the JMPC, the therapists try to help the patients to void the affective irritation and the internal tension they clearly demonstrate. When the patients notice that the therapists accept their distress, they usually talk more calmly about their hearing irritation and even consider it tolerable. The medical and psychological information given during the JMPC helps the patients to understand the links between tinnitus and the disturbing elements of their current life. During the JMPC, the medical residents have been able to observe how somatic complaints can lead to complaints of another nature, to distress, to aggressive or angered behaviors. They have acknowledged the way the psychologist deals with the attitudes of these patients. This learning process became mandatory to all our residents specializing in ENT. At the end of their training they should have learned how to help the patient accept the tinnitus and the irritation it causes. They should be able to help tinnitus patients to stop searching for a treatment that does not exist in the so-called specialized centers, which often do not fulfill their expectations.

Interventions médico-psychothérapeutiques en ORL: nouvelle approche pour les patients souffrant de la maladie de Menière

La consultation conjointe médico-psychologique (CCMP) est une technique de prise en charge dans laquelle deux thérapeutes, un somaticien et un psychologue, reçoivent les patients. Le principe fondamental sur lequel repose la CCMP consiste dans le fait que les deux thérapeutes sont présents, ensemble, du début à la fin de la consultation. Cet article décrit le déroulement d’une CCMP pour les patients souffrant d’une maladie de Menière et rapporte l’expérience acquise depuis son instauration en 1992. Outre les manifestations physiques bien connues, la maladie de Menière entraîne une modification temporaire de la personnalité du malade. La CCMP aide les patients à exprimer la dualité de leur affection, somatique et psychique. Tous les aspects de la maladie y sont donc abordés et pris en charge.