Abstract Otology 2000 C10-1

New electrode concepts for cochlear implant systems

Thomas Lenarz MD

HNO-Klinik Medizinische Hochschule Hannover D-Hannover

Apart from the development of new speech coding strategies improvements in cochlear implant systems can be achieved by new electrode concepts which provide more focused electrical stimulation at a low level of stimulus intensity. This allows an increase of the number of independent channels and electrode contacts in the cochlea, which is a prerequisite to imitate more physiological stimulation of remnant auditory nerve fibres. Several proposals have been put forward to achieve this goal. The common principle focuses on modiolus proximity and smaller contacts close to the nerve fibres. Different designs of modiolus-hugging electrodes were evaluated step by step with temporal bone studies, acute and chronic animal experiments, intraoperative measurements and clinical studies to evaluate their effectivity and safety. Electrode locations close to the modiolus result in decreased stimulus levels and power consumption and better channel separation. More patients can use simultaneous stimulation strategies, which offer new speech coding potentials. However, not all designs proved to have the level of safety required for chronic human use. Wires or strips pressed to the lateral wall and forcing the tip of the electrode towards the apex result in considerable destructin of the basilar membrane and induce cochlear obliteration. Electrodes with up to 50 contacts have been developed. They allow for tripolar, quadrupolar and jitter stimulation for pseudorandomized discharge patterns of the auditory nerve fibres to imitate the natural excitation process by acoustic stimulation. The progress in electrode development will lead to better performance in implanted patients.

Abstract Otology 2000 C10-2

Cochlear implantation deep insertion surgery

Caglar Batman MD, Selcuk Inanlý MD, Alper Tutkun MD, Mehmet Ali Pehitoglu MD

ENT Department Marmara University Hospital KBB Klinigi TR-Marmara-Altunizade

Intracochlear electrode placement in cochlear implant surgery is performed to maximize the chance of stimulating auditory nerve fibres as well as spiral ganglion cells. There are various electrode insertion length of the Nucleus electrode with different approaches. It is needed to insert more length about 30 mm to reach middle and appical cochlear turns. Electrode placement in these cochlear regions would improve the probability of stimulating surviving nerve fibers and provide a better correlation to cochlear tonotopy. In our study a surgical technique is presented in the last 20 patients out of our total 52, which demonstrated the feasibility of inserting the Nucleus electrodes entirely.

Abstract Otology 2000 C10-3

Intraoperative recording of neural responses to cochlear implant stimulation

Norbert Dillier Ph.D., WaiKong Lai PhD, Thomas Linder MD

Labor für Experimentelle Audiologie ORL-Klinik Universitätsspital CH-Zürich

Electrically evoked compound action potentials (EAP's) provide an objective means of assessing the condition of the auditory nerve in the vicinity of a stimulating electrodes. Neural Response Telemetry (NRT) measurements have been successfully performed with children and adults, both intra- and post-operatively. This presentation summarizes results of intraoperative measurements which were performed since October 1996 in 30 patients in the Department of Otorhinolaryngology of the University Hospital in Zürich. 26 patients (87 %) demonstrated clearly identifiable neural responses while in 4 patients no neural responses or only very small responses could be obtained at the time of surgery. Compared to EABR measurements which require a more elaborate setup, the recording of EAP's provides a significantly faster and more convenient form of objective assessment at the peripheral level. The data collection for all 22 intracochlear electrodes at three or four stimulation levels can be completed in less than 10 minutes while the calculation and extrapolation of amplitude growth functions and response thresholds can be performed automatically offline. Of particular interest are the implications of these measurements to processor fitting procedures for young children.

Abstract Otology 2000 C10-4

Children's implant profile (CHIP) predicts the outcome of paediatric cochlear implantation

Thomas P. Nikolopoulos MD, PhD, Kevin P. Gibbin , D. Dyar MD, Gerald M. O'Donoghue M.Ch FRCS

E.N.T Department Nottingham University Hospital GB-Nottingham

Introduction: The Children's Implant Profile (CHIP) was developed in New York Children's Hearing Institute1 as a systematic means of assessing the children before cochlear implantation. A slightly modified version by Nottingham Paediatric Cochlear Implant Programme (ChiP) evaluates 12 pre-implant factors: chronological age, duration of deafness, medical/radiological findings, functional hearing ability, speech and language abilities, multiple handicaps, family structure and support, educational environment, availability of support services, expectations of family/child, cognitive ability, and learning style. The aim of this prospective study was to assess the value of ChiP in predicting the functional outcome following cochlear implantation. Material and methods: 64 implanted children were assessed pre-operatively with ChiP and then prospectively follow-up for 4 years after implantation with Categories of Auditory Performance (CAP), Speech Intelligibility Rating (SIR)2, and Connected Discourse Tracking (CDT). Results: Speech intelligibility at 4 years was strongly correlated with pre-operative Chip (Spearman Rank coefficient -0.53, p<0.00001). Auditory perception as measured by CAP and CDT, at the same interval, were also significantly correlated with Chip (Correlation Coefficients -0.46 and -0.67 respectively with p<0.001). The most important predictive factors of ChiP were the duration of deafness, pre-operative speech and language abilities, and the pre-operative educational environment. Conclusion: The results of the present study suggest that the pre-operative ChiP is a significant predictor of the auditory perception and speech intelligibility of implanted children, 4 years following cochlear implantation. This has important clinical impact in the pre-operative assessment of children who are candidates for cochlear implantation. References 1. Hellman SA, Chute PM, Kretschmer RE, Nevins ME, Parisier SC, Thurston LC. The development of a children's implant profile. Am Ann Deaf 1991; 136(2): 77-81. 2. Allen C., Nikolopoulos T, O'Donoghue G. Speech Intelligibility in children following cochlear implantation. Am J Otol 1998: 19(6): 742-746.

Abstract Otology 2000 C10-5

Short and long term results with fast stimulator cochlear implants - The Würzburg experience using the MedEl Combi 40 and Combi 40+ Cochlear Implant

Joachim Müller MD, L. Scholtz MD, M. Herzog MD, F. Schön MD, Jan Helms MD

Department of ENT-HNO Julius-Maximilians-Universität D-Würzburg

Based on the evaluation of more than 260 cochlear implants patients the results for different subgroups are presented: Subgroup A: With improved speech understanding also the indication for a cochlear implant in patients with residual hearing must be discussed in comparison to conventional hearing aids. The results of patients with residual hearing were discussed in comparison to our results in totally deaf patients and in comparison to the literature. This patients population is divided in different groups: 1. Patients with residual hearing on one ear. Deaf ear implanted. 2. Patients with residual hearing for environmental sounds on both ears or minimal speech understanding (numbers<30%) in the best aided binaural condition. Worst ear implanted. 3. Patients with remaining open set speech understanding in both ears. One ear with remaining open set speech understanding implanted. The paper discusses the results of patients with residual hearing in detail and gives our current guide-lines for cochlear implantation in patients with residual hearing. Subgroup B: Modern cochlear implants using the fast CIS strategy improved the speech understanding in cochlear implant patients. Therefore, this improved speech understanding may help senior citizens with a long history of sensory neural hearing loss to avoid complete deafness and social isolation. The paper analyses in addition the results after the cochlear implantation in patients age 65 to 79 years in comparison to our results in younger patients and in comparison to the literature.

Abstract Otology 2000 C10-6

Multicentric evaluation of the new MED-EL TEMPO+ ear level speech processor for COMBI 40 / COMBI 40+ cochlear implants

Jan Helms MD (1), Wolfgang Gstöttner MD (2), Wolfgang Arnold MD (3), Joachim Müller MD (1), Wolf-Dieter Baumgartner MD (2), F. Schön MD (1), S. Brockmeier MD (3), B. Stöbich MD (4), M. Zwicknagl PhD (4), Ingeborg Hochmair-Desoyer PhD (4)

(1) HNO-Klinik Julius-Maximilians-Universität D-Würzburg
(2) ENT Department University of Vienna A-Wien
(3) HNO-Klinik Univ.-Klinik Rechts der Isar D-München
(4) University of Innsbruck A-Innsbruck

Multicentric clinical studies involving 19 European cochlear implant centers are being conducted to evaluate speech perception with the MED-EL COMBI 40 and the COMBI 40+ cochlear implants in postlingually deafened adults. Data on 2-digit numbers, monosyllabic words, on everyday senctences and on HSM-sentences in quiet and for various signal-to-noise ratios (CCITT-noise) are available for up to 4 years follow up with the COMBI 40 implant and 2 years follow up with the COMBI 40+ implant. Within the study the high rate CIS strategy implemented in the body worn processor with 8 channels at 1500 pulses per second per channel (12000 pps overall) with the COMBI 40 and with 12 channels at 1500 pulses per second per channel (18000 pps overall) with the COMBI 40+ has been used. Monosyllabic word understanding in the German speaking subgroup of patients (50 for the COMBI 40 and 40 for the COMBI 40+) has been found to have a mean value of 54.4% for the COMBI 40 patients and 61.0 % for the COMBI 40+ patients at 1 year post first fitting. Both, COMBI 40 and COMBI 40+ patients, have participated in an evaluation of the new ear level speech processor TEMPO+, which has recently become available and which implements the CIS+ speech coding strategy at the same stimulation rate (12000 pps overall for COMBI 40 and 18000 pps overall for COMBI 40+) and gereral number as the body worn processor. The TEMPO+ study protocol included tests for monosyllabic words and Göttinger sentences for the body worn and the ear level speech processor at the time of TEMPO+ fitting and after using the TEMPO+ for 1 month. Because of possible ceiling effects scores were purposely reduced to around 50% by individually adding an appropriate noise level. The results show that the implementation of the CIS+ strategy in the ear level processor (including the Hilbert transform for envelope extraction, but not yet using the available possibility of a wider frequency range) leads to a statistically significant increase in scores for monosyllabic words and Göttinger sentences, both at time of TEMPO+ fitting and after 1 month of TEMPO+ use.

Abstract Otology 2000 C10-7

Comparision of different speech coding strategies with the nucleaus CI 24M cochlear implant

Thomas Pfennigdorff MD, Jan Kiefer MD, Christoph Von Ilberg Prof.Dr.

ENT Department Universität Frankfurt W-Frankfurt a. M.

Progress in cochlear implant technology, as well as further developments in speech coding strategies, has considerably increased performance levels in implanted patients. To quantify the benefit of these strategies, we present a within-subject comparision using SPEAK-, CIS- or ACE speech coding strategies with the Nucleus CI 24M cochlear implant. The performance was evaluated after optimal fitting and after at least three months experience with one of the above mentioned speech coding strategies. Following tests were performed in 10 postlingually deafened adult patients with a cochlear implant: numbers, monosyllabic words, vowels, consonants, speech perceptions in quiet and in noise with 'Innsbruck' and 'Göttinger' sentence tests. Our study was divided into two groups of patients. The first group of patients was initially fitted with SPEAK-strategies, after three months we changed to CIS- and finished with ACE speech coding strategies. In the second group, we started with CIS-strategies, changed to SPEAK- and finished with ACE speech coding strategies. Neuronal responses of the auditory nerve (NRT) were also recorded from all 10 patients. In general all of the patients reached open set speech understanding with each of the three speech coding strategies. The results showed better performance with the fast speech coding strategies CIS and ACE for most of the patients. The differences were statistically significant and were greatest for sentence tests in noise. So far, no correlation between NRT-results and performance with different speech coding strategies were found.