Techn. Universiẗat, Diss., 2006--München.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. Includes bibliographical references (leaves 234-241).

Diplomarbeit AGSA 6, Hochschule für Heilpädagogik Zürich, 2009.

Dissertation (Ph.D.)--University of Toledo, 2005. / Typescript. "A dissertation [submitted] as partial fulfillment of the requirements of the Doctor of Philosophy degree in Engineering." Bibliography: leaves 128-141.

Cochlear implants have successfully been used to enable hundreds of thousands of profoundly deaf people to regain some perception of hearing. Hearing performance does, however, vary greatly among individual implant users. In order to gain a better understanding of the underlying factors that cause these inter-user performance differences, insight into the functioning of individual implant users’ hearing systems is required. Some of the parameters unique to an implanted user’s hearing system may be measured non-invasively using psychoacoustics or the measurement of electrically evoked compound action potentials. While these methods provide information of the macro response of a user’s hearing system to stimulation, individual parameters, for example the individual neurons that are excited cannot be measured. Some individual parameters are difficult or even impossible to measure in a living human as it is not technically feasible or invasive surgery is required. When obtaining measurements inside the inner ear of a living human is not an option, an alternative that mimics the human hearing system is required from which measurements can be predicted: models. This study describes the development of a method to construct an electrical computational three-dimensional finite element model of the implanted cochlea of a specific living individual. This method is presented as a tool for researchers to probe the cochleae of specific implanted users non-invasively. Data from a low resolution computer tomography scan is used to construct a geometric representation of the bony outer cochlear structures and augmented with histologic data to construct the smaller inner cochlear structures. A detailed skull geometry with brain and scalp volumes that includes the user’s return electrode is also constructed. The user’s electrode array is modelled in its intra-cochlear location and stimulation is simulated using finite element modelling. The cochleae of five individual ears were modelled and intra-cochlear and neural node potentials were predicted along with neural excitation patterns. Having models that can predict user-specific outcomes, predictions that include the variability between implanted ears are obtained. This allowed the comparison of modelled data to common trends found in literature and enabled the investigation of questions frequently asked by modellers. These include the effect that bone resistivity, head volume shape, return electrode implementation and return electrode position have on modelled results. These findings were incorporated and contributed to higher detailed models being produced than are currently described in literature. The models were then practically applied in two areas. The first was in the quantification of potential decay in the cochlea where a simple model is derived to predict decay at the neuron level based on the location of an electrode. The second was in the translation of the model into the clinical domain where the mismatch between the perceived pitch and mapped frequencies of specific implanted individuals were predicted. Along with these predictions it was found that neural excitation and intra-cochlear potential spread are highly dependent on individual cochlear morphology. This warrants the inclusion of user-specific morphology in volume conduction models of the implanted cochlea where user-specific outcomes are predicted. / Thesis (PhD (Electronic Engineering))--University of Pretoria, 2015. / Electrical, Electronic and Computer Engineering / PhD (Electronic Engineering) / Unrestricted

Telephones are an integral part of everyday life in today's society. It is well known that hearing impaired people have difficulty understanding speech on the telephone. The ability to use the telephone is commonly reported as one of the many benefits of cochlear implantation. Assessment for a cochlear implant (CI) includes a variety of aspects related to communication and hearing ability. Included in the case history, mention is made whether the person can use the telephone. The purpose of the present study was firstly to identify if the inability to use the telephone could be used a predictor for suitability for a cochlear implant. It was also purposed to determine if telephone ability could be assessed by self-reported measures. The participants were 13 severe to profoundly hearing impaired people who had previously undergone candidacy assessment for a cochlear implant. Each participant was evaluated on their use and understanding of speech on the telephone. Participants were separated into two groups: those who were candidates for a cochlear implant and those who were not. Speech perception testing was evaluated using a recording of CUNY sentences on the telephone. Results indicated that cochlear implant candidates correctly perceived a significantly lower number of words on the telephone than non-candidates. Use of the telephone was evaluated using a 51-item questionnaire. Results indicated that there was no significant difference in self-reported use of the telephone between cochlear implant candidates and non-candidates. The differences in speech perception understanding on the telephone were most likely due to the overall better hearing levels of the non-candidates. The clinical implications of the present study are considered.

Most previous research into cochlear implant (CI) mediated music listening deals with the mechanisms and efficacy of music perception and does not often account for the listeners real-world musical experience. Measurements of music perception ability are based on listening tasks such as pitch-discrimination, timbre-recognition and rhythmic-identification, and rarely (if ever) relate to the individual experience of the human subject. The exploration of musical experience, however, is based on a holistic view of the ways in which individual people experience music, which can be informed by the interaction of a multitude of factors. For the purposes of this thesis, three categories of experience are considered to coalesce to inform the general musical experience: sensory experience, cognitive experience and social/environmental experience. This thesis moves towards consideration of the real-world musical experiences of cochlear implant users (CIUs) with a view of developing strategies that can be implemented to improve those elements of the musical experience that may be problematic. The thesis comprises three main sections as follows: The first section investigates the musical experiences of CI users (CIUs) by means of a questionnaire study and the consideration of information gained from music focus groups and conversations with implant users. Results show a great deal of variability in the musical experiences of CIUs but many people report positive experiences of music despite suffering from what may be described as ‘poor’ music perception. The second section outlines the design, development and implementation of a multi-channel mixer application, which is used in a study exploring the way in which CIUs mix multi-channel music, to gain insight into their experience of musical elements. Analysing the user-generated mix data provides considerable insights into various elements of the musical experience of participants. Again, results show a large degree of variability on this issue amongst CIUs, and also that the average mixes of CIUs differ significantly from that of a control group of normal-hearing (NH) participants. The third section describes the composition, development and evaluation of a musical work specifically composed for CIUs but designed to be enjoyable for both CIUs and NH audience members alike. The aim of this composition is to promote a positive musical experience by addressing elements of the sensory, cognitive and social/environmental experience based on findings of this research. This thesis concludes by suggesting that the ideal approach for improving the musical experiences of CIUs should focus on the individual, due to the great deal of variability within this population, and presents some implications of this work and suggestions for future research in this area.

Seit ca. 15 Jahren (1991) werden taube und hochgradig schwerhörige Patienten mit einem Cochlea-Implantat (CI) an der Klinik für Hals-, Nasen- und Ohrenkranke der Universität Würzburg versorgt. Insgesamt wurden (Stand Juni 2008) über 1100 CIs implantiert. Das Cochlea-Implantat übernimmt prothetisch die Aufgabe des Innenohres und stimuliert direkt den Hörnerv. Zur Feststellung der Stimulierbarkeit des Hörnervs wird präoperativ mit einer Gehörgangselektrode oder einer Promontoriumsnadel elektrisch gereizt. Bei erwachsenen Patienten wird zusätzlich, nach geeigneter Festlegung der Lautheit, ein Test des Zeitauflösungsvermögens durchgeführt. Hierzu wird vom Patienten in einem adaptiven 3-aus-1 - Auswahlverfahren der eben wahrnehmbare Unterschied in der Dauer dreier Stimulustöne erfragt. Der resultierende Wert wird als „TDL“-Wert („temporal difference limen“) bezeichnet. Im Rahmen der vorliegenden Dissertation wurde das Zeitauflösungsvermögen anhand des TDL-Tests im Vergleich zur präoperativen Leistung und der Zusammenhang mit dem Sprachverständnis untersucht. Die Messungen erfolgten an einem Kollektiv von 40 Patienten, die unilateral mit einem Cochlea-Implantat der Firma MED-EL versorgt worden waren. Der TDL-Test wurde postoperativ bei 4 Frequenzen (500, 1000, 2000, 4000 Hz) durchgeführt. Die präoperativen TDL-Werte (Median: 106 ms) sind statistisch signifikant (p < 0,001, Wilcoxon-Test) größer als die postoperativen (Median der Mittelwerte bei vier Frequenzen: 54 ms). Demzufolge hat sich das Zeitauflösungsvermögen nach Cochlea-Implantation deutlich verbessert. Als Erklärung kommen in Frage: eine bessere zentral-kognitive Hörleistung aufgrund des alltäglichen Hörtrainings mit dem CI-System; eine Verbesserung der Zeitauflösung durch chronische elektrische Stimulation; eine direktere Reizung der Nervenfasern bei CI (intracochleäre Stimulation) gegenüber extracochleärer Stimulation präoperativ; eine verläßlichere Festlegung der Reizstärke aufgrund des besseren Lautheitsbeurteilungsvermögens postoperativ. Im allgemeinen Vergleich gibt es nur schwache Korrelationen (0,42) zwischen dem präoperativen und den postoperativen TDL-Werten. Ein Zusammenhang mit den Stimulationsfrequenzen, d. h. mit dem Stimulationsort in der Cochlea existiert nicht. Die Interkorrelation zwischen den postoperativen TDL-Werten ist hoch (Korrelationskoeffizienten zwischen 0,72 und 0,91). Die postoperativen TDL-Werte unterscheiden sich bei den vier untersuchten Frequenzen nur geringfügig (Medianwerte zwischen 42 ms und 54 ms). Die Unterschiede sind in keinem Vergleichsfall signifikant (p > 0,2, Wilcoxon-Test). Zwischen den Resultaten der Sprachverständnistests „Freiburger Zahlen“ (FZ), „Freiburger Einsilber“ (FE) und „HSM-Satztest“ (HSM) untereinander gibt es einen mäßig starken Zusammenhang (Korrelationskoeffizienten zwischen 0,46 und 0,62). Ein Zusammenhang des Sprachverständnisses mit dem präoperativen TDL-Wert ist nicht vorhanden (Korrelationskoeffizienten zwischen 0,036 und 0,18), mit dem postoperativen TDL-(Mittel-)Wert ist gering (Korrelationskoeffizienten zwischen 0,1 und 0,35). Abschließend muß festgestellt werden, dass der TDL-Test keine brauchbare Vorraussage über den Hörerfolg mit dem CI macht. Der TDL-Test kann also nicht zur Entscheidung für oder gegen die Versorgung mit einem CI herangezogen werden. In der Konsequenz stellt sich die Frage, ob eine Durchführung lohnt. / Since about 15 years (1991), patients with profound hearing loss are provided with cochlear implants (CIs) at the department of otorhinolaryngology of the University of Würzburg. To date (May 2007), more than 1000 cochlear implants have been implanted. The CI is an implantable auditory prosthetic device that substitutes a nonfunctional cochlea. In order to assess the ability of conveying information to the central nervous system, a preoperative test is conducted, where the inner ear is stimulated electrically via an ear-canal electrode or a transtympanic promontorial needle. In adult postlingually deafened patients, an additional test is conducted, where temporal resolution is assessed via an adaptive 3 alternative forced choice procedure. In this procedure, the just noticable difference in the duration of test tones is acquired. The resulting value is referred to as "TDL" ("temporal difference limen"). In this thesis, the temporal resolution of experienced CI subjects as measured by the TDL test was investigated and compard to their preoperative performance. Also, the correlation with speech understanding was examined. Measurements were conducted with 40 unilaterally implanted subjects, all of them used a Med-El CI-system. The postoperative TDL-Test was conducted at frequencies 500, 1000, 2000 and 4000 Hz. Preoperative TDL-values (median: 106 ms) were significantly larger (p < 0.001, Wilcoxon-test) than postoperative values (median of means at four frequencies: 54 ms). Accordingly, the temporal resolution capability has significantly improved after cochlear implantation. Possible explanations are: improved central-cognitive auditory performance caused by everyday listening with the CI; improved temporal resolution on the peripheral level due to chronic stimulation; more direct stimulation because of the intracochlear placement of the electrode (CI) versus extracochlear stimulation preoperatively; more reliable adjustment of stimulation level due to better loudness judgment capabilities of subjects. Generally, only a weak correlation (0.42) between pre- and postoperative TDLs could be found. A connection between TDLs and stimulation frequencies, i.e. the place of stimulation within the cochlea, could not be demonstrated. Intercorrelation between postoperative TDL values is high (correlation coefficients from 0.72 to 0.91) Postoperative TDL values of the four tested frequencies differ only marginally (median values from 42 ms to 54 ms). Differences are not statistically significant in any of the comparisons (p > 0.2, Wilcoxon-test). Between the speech understanding results of "Freiburger Zahlen" (two digit numbers), "Freiburger Einsilber" (monosyllabic words) and "HSM-test" (everyday sentences) moderate correlations were found (correlation coefficients from 0.46 to 0.62). Correlation between speech performance and preoperative TDL value is virtually non-existent (correlation coefficients from 0.036 to 0.18), correlation between speech performance and postoperative TDL is weak (correlation coefficients from 0.1 to 0.35). It must be concluded, that preoperative TDL-values do not predict the success with the CI, at least not for speech understanding as measured with the three tests used here. Thus, the TDL does not serve as a tool in making a decision about whether to provide an implant or not. Consequently, it is questionable, whether performing the test is worthwhile.

In der vorliegenden Arbeit wurden die Daten von 37 Patienten der Neurootologischen Abteilung der Klinik und Poliklinik für Hals-, Nasen- und Ohrenkrankheiten, plastische und ästhetische Operationen der Universitätsklinik Würzburg retrospektiv ausgewertet. Alle Patienten wurden einer prä- und einer postoperativen vestibulären Prüfung unterzogen und wurden zwischen 1999 und 2008 unilateral implantiert. Versorgt wurden sie mit einem Cochlea-Implantat der Firma Med-El Corp., vom Typ C40+, C40++ oder PulsarCI100. Neben der speziellen neurootologischen Anamnese wurde bei den Patienten der Spontannystagmus, eine kalorische Nystagmusprüfung, rotatorischer Intensitäts-Dämpfungs-Test (RIDT), vestibulärer Reiz-/Reaktions-stärkevergleich (VRRSV) und Cranio-Corpo-Graphie (CCG) vor und nach Implantation erhoben. Die Einzelbefunde der vestibulären Tests wurden vor und nach Implantation zusammengetragen und es wurde jeweils eine neurootologische Diagnose erstellt. Typische Beispiele fanden als Kasuistik Eingang. Als Fazit ergaben sich folgende 3 Hauptaussagen: Bei dem Großteil der Patienten (83,8%) lag bereits präoperativ eine Schädigung des vestibulären Systems vor. Im ausgewerteten Kollektiv lag das Risiko für eine Veränderung der empfundenen Vertigosymptome bei der Gruppe mit Vertigosymptomen bereits vor Implantation wesentlich höher als bei der Gruppe ohne präoperative Vertigosymptome. Bei knapp der Hälfte der Patienten veränderte sich der vestibuläre Zustand durch die Implantation. Die Veränderungen können sowohl im Sinne einer Verbesserung meist jedoch als Verschlechterung auftreten und dies auf der implantierten als auch auf der nicht-implantierten Seite. Auffallend ist die hohe Diskrepanz zwischen dem objektiven Zustand und dem subjektiven Empfinden der Patienten. Die Ergebnisse unterstreichen die Notwendigkeit einer neurootologischen Untersuchung vor einer Cochlea-Implantation. Da die Ursachen für die Beeinflussung vor allem der nicht-implantierten Seite noch nicht geklärt sind, ist eine umfassende Aufklärung mit Betrachtung der individuellen vestibulären Situation, auch zum Schutz des Operateurs, unumgänglich. / change of the vestibular function in patients with unilateral cochlear implantation

Hearing loss is a common impairment or disability for human beings, and is impacting an increasing amount of people, augmented by the growing aging population around the globe. Cochlear implantation, as one of the most effective ways to restore hearing, can only applied to profoundly deaf patients at the moment. In order to expand the group of people who can benefit from cochlear implantation to those with less severe hearing loss, endeavours need to be made to best preserve residual hearing and minimise trauma induced during cochlear implantation surgery. In this thesis, the disturbance induced in the cochlea, i.e. the acoustic and mechanical energy transmitted into the cochlea, during cochleostomy drilling is studied - as well as establishing a comparison between a manually guided conventional technique and a manually supported tissue guided robotic drilling technique. The results show that by changing surgical techniques and how they are applied can have a significant impact on levels of disturbance induced - robotic-aided approach induced lower level of equivalent SPL for up to 86% of the time and can be as much as 39 dB lower than that generated by conventional surgical drilling. This work is timely because trauma is an important consideration to clinicians and health care providers. Cochleostomy is one of the major and most disruptive surgical process during cochlear implantation. With the increasing amount of cochlear implant electrode array designs that are shorter and less intrusive, and the increasing demand of electric-acoustic stimulation via cochlear implant to better resemble the human auditory system, the approach to reduce disruption during cochleostomy drilling is highly relevant to the progression in the hearing care industry and the benefits of the growing hearing impairment community.