The relationship between binaural benefit and difference in unilateral speech recognition performance for bilateral cochlear implant users

Abstract

Objective: The full benefit of bilateral cochlear implants may depend on the unilateral performance with each device, the speech materials, processing ability of the user, and/or the listening environment. In this study, bilateral and unilateral speech performances were evaluated in terms of recognition of phonemes and sentences presented in quiet or in noise. Design: Speech recognition was measured for unilateral left, unilateral right, and bilateral listening conditions; speech and noise were presented at 0° azimuth. The ‘binaural benefit’ was defined as the difference between bilateral performance and unilateral performance with the better ear. Study sample: Nine adults with bilateral cochlear implants participated. Results: On average, results showed a greater binaural benefit in noise than in quiet for all speech tests. More importantly, the binaural benefit was greater when unilateral performance was similar across ears. As the difference in unilateral performance between ears increased, the binaural advantage decreased; this functional relationship was observed across the different speech materials and noise levels even though there was substantial intra- and inter-subject variability. Conclusions: The results indicate that subjects who show symmetry in speech recognition performance between implanted ears in general show a large binaural benefit.

Sumario

Objetivo: Se estudiaron los datos audiológicos de investigación epidemiológica basada en una población de adultos mayores. Se buscaron diagnósticos específicos de alteraciones otológicas y audiológicas que pueden ocasionar hipoacusia. Diseño: Estudio retrospectivo de registros. Muestra: Se estudiaron tres cohortes etáreas, 474 individuos de 70 a 75 años (“jóvenes) y 252 individuos de 85 años o mayores (“viejos”). Se utilizaron las audiometrías de tonos puros y de lenguaje. Se incluyeron los datos de sus expedientes médicos. Resultados: Se diagnosticó hipoacusia conductiva en 6.1% del grupo de “jóvenes” y un 10.3% de los “viejos”. Se establecieron diagnósticos especfícos (otitis media crónica y otoesclerosis) en cerca de la mitad de los casos. Se diagnosticó hipoacusia sensorineural no relacionada con la edad ni inducida por ruido en 3.4 y 5.2% de los casos. El 0.4% del grupo de “jóvenes” y el 10% del grupo de “viejos” presentaban un reconocimiento del lenguaje severamente afectado, posiblemente relacionado con neuropatía auditiva por edad. El 3.2% de las personas de 85 años de edad presentaban sordera funcional bilateral, pero ésta no se presentó en el grupo de 70–75 años. Conclusiones: La incidencia de neuropatíaa auditiva probablemente relacionada con la edad aumenta considerablemente de los 70–75 años a los 85. Existen marcadas diferencias en cuando a hipoacusia que afecta severamente la comunicación entre los grupos de “jóvenes” y “viejos” en la población estudiada.

Key Words::

• Cochlear implant
• Speech perception
• Binaural hearing
• Signal-to-noise ratio

Acknowledgments

We thank our participants for their time and effort. We thank John J. Galvin III, Jaesook Gho, and Joseph Crew for their comments and editorial assistance. This study was presented in part at the 33rd Association for Research in Otolaryngology (ARO), under the title of The Benefits and Perceptual Mechanism by Bilateral and Bimodal Cochlear Implant Users, in February 2010, in Anaheim, California, USA.

Declaration of interest: This work was supported by NIH grant 5R01DC004993.