SPATIAL HEARING AND MUSIC PERCEPTION ABILITIES IN SUBJECTS USING A COMBINATION OF ELECTRIC AND ACOUSTIC STIMULATION

Cowan RSC (1, 4), Plant KL (1, 2), Briggs R (1, 4), Whitford LA (1, 2), Law M (1, 2), Incerti P (1, 2), Gorrie J (1, 2), Skinner L (1, 2, 3 ).

(1) The HEARing CRC, Melbourne, Australia; (2)  Cochlear Limited, Melbourne, Australia; (3) The Sydney Cochlear Implant Clinic, Sydney, Australia; (4) The Department of Otolaryngology, University of Melbourne, Australia.

Objectives: A number of recent studies have reported preservation of acoustic low-to-mid frequency hearing in cochlear implant recipients following careful surgical insertion techniques and using new electrode technology.  Such recipients have the potential to make use of both acoustic hearing and electrical stimulation delivered to the same ear.  The aim of this clinical study was to assess the potential benefit of use of the residual hearing in the implanted ear.

Materials and Method: The benefits of ipsilateral acoustic hearing was assessed in twelve adult cochlear implant recipients.  All subjects were implanted with either the Nucleus Contour Advance or a specialised Hybrid-L24 electrode array.  Benefits were assessed through comparing test outcomes for a ‘combined’ condition - using the cochlear implant together with an both an ipsilateral and contralateral hearing aid, with a ‘bimodal’ condition - using the cochlear implant with only a contralateral hearing aid.  All subjects received a minimum of months experience after initial activation prior to assessments.  Localisation ability was measured using an 8-speaker array with a 180-degree span.  Speech perception was evaluated in a range of speaker configurations to measure spatial hearing abilities.  Musical tests included pitch ranking of sung vowels, identification of stretched or compressed melodies and sound quality ratings. 

Results: For most subjects, performance in the combined condition was superior to that for the bimodal condition for tests of speech perception in noise, sound localisation, musical sound quality ratings and functional performance in real-world listening situations.  No measurable improvement was observed on objective music tests. 

Discussion & Conclusion: The potential benefits of use of an ipsilateral hearing aid fitted with a cochlear implant should be communicated to cochlear implant candidates, and considered for all patients who show preservation of residual hearing postimplantation. 

E-mail: r.cowan@unimelb.edu.au