Sound localization and speech intelligibility were assessed in 5 patients implanted bilaterally with Medel C40+ or Medel C40 cochlear implant (CI) systems. The minimum audible angle (MAA) around the head in the horizontal plane was assessed in patients with bilateral CI using white noise bursts of 1000 ms duration presented from a loudspeaker mounted on a rotating boom and compared with the MAA of age-matched normal hearing controls. Spatial discrimination was found to be good in front and in the back of the head with near-normal MAA values (patients: 3–8°, controls: 1–4°). In contrast, poor performance on the sides was found (patients: 30 to over 45°, controls 7–10°). Bilateral CI significantly improved spatial discrimination in front for all patients, when compared with the use of either CI alone. Just noticeable differences (JNDs) in interaural intensity and time were assessed using white noise bursts (1000 ms duration; 50 ms linear ramp). In addition, interaural time JNDs were assessed using click trains (800 ms duration, 40 µs clicks, 50 Hz) and noise bursts in which either only the envelope or only the fine structure was shifted in time. In comparison with normal hearing controls, patients with bilateral CI showed near-normal interaural intensity JNDs but substantially poorer interaural time JNDs depending on the type of stimulus. In contrast to envelope onset/offset cues, interaural fine structure time differences were not perceived by the patients using CI systems employing the continuous interleaved sampling strategy without synchronization between their pulse stimulation times. Speech intelligibility in quiet and CCITT noise from the side (±90°) was assessed using the German HSM sentence test and was significantly better when using bilateral CI in comparison with either unilateral CI, mainly due to a head shadow effect. These favorable results are in agreement with the patients’ subjective experiences assessed with a questionnaire and support the use of bilateral CI.

Arlinger S: Negative consequences of uncorrected hearing loss – a review. Int J Audiol 2003;42(suppl 2):2S17–2S20.
Arlinger S, Gatehouse S, Bentler RA, Byrne D, Cox RM, Dirks DD, Humes L, Neuman A, Ponton C, Robinson K, Silman S, Summerfield AQ, Turner CW, Tyler RS, Willott JF: Report of the Eriksholm Workshop on auditory deprivation and acclimatization. Ear Hear 1996;17:87S–98S.
Au DK, Hui Y, Wei WI: Superiority of bilateral cochlear implantation over unilateral cochlear implantation in tone discrimination in Chinese patients. Am J Otolaryngol 2003;24:19–23.
Brunner EH, Langer F: Non-parametric analysis of longitudinal data (in German). Munich, Oldenburg, 1999.
Byrne D: Clinical issues and options in binaural hearing aid fitting. Ear Hear 1981;2:187–193.
Byrne D, Noble W, LePage B: Effects on long-term bilateral and unilateral fitting of different hearing aid types on the ability to locate sounds. J Am Acad Audiol 1992;3:369–382.
Gantz BJ, Tyler RS, Rubinstein JT, Wolaver A, Lowder MW, Abbas P, Brown C, Hughes M, Preece JP: Binaural cochlear implants placed during the same operation. Otol Neurotol 2002;23:169–180.
Hartmann WM, Rakerd B: On the minimum audible angle – a decision theory approach. J Acoust Soc Am 1989;85:2031–2041.
Häusler R: Cochlear implantation without mastoidectomy: the pericanal electrode insertion technique. Acta Otolaryngol 2002;122:715–719.
Häusler R, Colburn S, Marr E: Sound localization in subjects with impaired hearing. Spatial-discrimination and interaural-discrimination tests. Acta Otolaryngol Suppl (Stockholm) 1983;400:1–62.
Helms J, Müller J, Schön F: Evaluation of performance with the COMBI 40 cochlear implant in adults: a multicentric clinical study. ORL 1997;59:23–35.
Hochmair-Desoyer I, Schulz E, Moser L, Schmidt M: The HSM sentence test as a tool for evaluating the speech understanding in noise of cochlear implant users. Am J Otol 1997;18 (suppl):83.
Hurley RM: Onset of auditory deprivation. J Am Acad Audiol 1999;10:529–534.
Kompis M: Directional multi-microphone noise reduction systems and binaural cochlear implantation. IFMBE Proc World Congr Med Phys Biomed Eng, Sydney, Australia, 2003, pp 1602–1605.
Kompis M, Jenk M, Vischer M, Seifert E, Häusler R: Intra- and intersubject comparison of cochlear implant systems using the ESPRIT and the Tempo+ behind-the-ear speech processor. Int J Audiol 2002;41:555–562.
Lawson DT, Wilson BS, Zerbi M, van den Honert C, Finley CC, Farmer JC, McElveen JT, Jr, Roush PA: Bilateral cochlear implants controlled by a single speech processor. Am J Otol 1998;19:758–761.
Long CI, Eddington DK, Colburn HS, Rabinowitz WM: Binaural sensitivity as a function of interaural electrode position with a bilateral cochlear implant user. J Acoust Soc Am 2003;114:1565–1574.
Mawman DJ, Ramsden R, O’Driscoll M, Adams T, Saeed S: Bilateral cochlear implantation – a case report. Adv Otorhinolaryngol 2000;57:360–363.
Mills AW: On the minimal audible angle. J Acoust Soc Am 1958;30:237–246.
Moore BCJ: An introduction to the Psychology of Hearing. London, Academic Press, 2003, pp 228–231.
Müller J, Schön F, Helms J: Speech understanding in quiet and noise in bilateral users of the MED-EL Combi 40/40+ cochlear implant system. Ear Hear 2002;23:198–206.
Schleich P, Nopp P, D’Haese P: Head shadow, squelch, and summation effects in bilateral users of the MED-EL COMBI 40/40+ cochlear implant. Ear Hear 2004;25:197–204.
Schön F, Müller J, Helms J: Speech perception thresholds obtained in a symmetrial four loudspeaker arrangement from bilateral users of MED-EL cochlear implants. Otol Neurotol 2002;23:710–714.
Tomblin JB, Spencer LJ, Gantz BJ: Language and reading acquisitions in children with and without cochlear implants. Adv Otorhinolaryngol 2000;56:300–305.
Tyler RS, Dunn CC, Witt SA, Preece JP: Update on bilateral cochlear implantation. Curr Opin Otolaryngol Head Neck Surg 2003;5:388–393.
Tyler RS, Gantz BJ, Rubinstein JT, Wilson BS, Parkinson AJ, Wolaver A, Preece JP, Witt S, Lowder MW: Three month results with bilateral cochlear implants. Ear Hear 2002a;23:80–90.
Tyler RS, Parkinson AJ, Wilson BS, Witt S, Preece JP, Noble W: Patients utilizing a hearing aid and a cochlear implant: speech perception and localization. Ear Hear 2002b;23:98–105.
Tyler RS, Summerfield AQ: Cochlear implantation: relationships with research on auditory deprivation and acclimatization. Ear Hear 1996;17:38S–50S.
van Hoesel R, Ramsden R, O’Driscoll M: Sound-direction identification, interaural time delay discrimination, and speech intelligibility advantages in noise for a bilateral cochlear implant user. Ear Hear 2002;23:137–149.
van Hoesel R, Tyler RS: Speech perception, localization, and lateralization with bilateral cochlear implants. J Acoust Soc Am 2003;113:1617–1630.
van Hoesel RJ: Exploring the benefits of bilateral cochlear implants. Audiol Neurootol 2004;9:234–246.
van Hoesel RJ, Clark GM: Fusion and lateralization study with two binaural cochlear implant patients. Ann Otol Rhinol Laryngol Suppl 1995;166:233–235.
van Hoesel RJ, Clark GM: Psychophysical studies with two binaural cochlear implants subjects. J Acoust Soc Am 1997;102:504–518.
van Hoesel RJ, Tong YC, Hollow RD, Clark GM: Psychophysical and speech perception studies: a case report on a bilateral cochlear implant subject. J Acoust Soc Am 1993;94:3178–3189.
Vermeire K, Brokx JPL, Van de Heyning PH, Cochet E, Carpentier H: Bilateral cochlear implantation in children. Int J Pediatr Otorhinolaryngol 2003;67:67–70.
Wilson BS, Finley CC, Lawson DT, Wolford RD, Eddington DK, Rabinowitz WM: Better speech recognition with cochlear implants. Nature 1991;18:236–238.
Wilson BS, Lawson DT, Muller JM, Tyler RS, Kiefer J: Cochlear implants: some likely next steps. Annu Rev Biomed Eng 2003;5:207–249.
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.