Hearing-in-noise benefits after bilateral simultaneous cochlear implantation continue to improve 4 years after implantation.
OBJECTIVE
The purpose of this 4-year longitudinal study was to assess the stability of the binaural benefits of head shadow, summation, and squelch for bilateral cochlear implant recipients and to quantify these benefits for the understanding of speech in noise.


METHODS
This is a prospective study of 9 patients who received simultaneous bilateral insertion of MED-EL COMBI +40 cochlear implants in a single-stage operation at the University of North Carolina, Chapel Hill, NC. Each patient had postlingual deafness of short duration before insertion of the device. Each year, the patients were tested for word recognition using consonant-nucleus-consonant words in quiet and speech perception in noise using City University of New York sentences. These tests were administered using direct audio input to the implants. Head-related transfer functions were used to simulate speech in noise testing in a spatial environment. Speech was always presented at midline (0 degrees), and the noise masker was presented at either side or midline (-90, 0, +90 degrees).


RESULTS
The binaural benefits of head shadow and summation effects developed early in the postoperative period and remained stable throughout the follow-up period. Squelch developed more slowly and was first demonstrated at 12 months after implantation but continued to increase beyond the first year of follow-up.


CONCLUSIONS
Benefits of head shadow and summation emerge early and remain stable. However, squelch has the most protracted period of development, with increasing benefit after a year or more of implant experience. These data support the idea that binaural integration continues several years after insertion of bilateral cochlear implant devices.
Eapen
Rose J
RJ
Department of Otolaryngology Head & Neck Surgery, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27514, USA.
Buss
Emily
E
Adunka
Marcia Clark
MC
Pillsbury
Harold C
HC
Buchman
Craig A
CA
D000161:Acoustic Stimulation; D000328:Adult; D000368:Aged; D019929:Cochlear Implantation; D003054:Cochlear Implants; D003638:Deafness / Q000523:psychology / Q000628:therapy; D004192:Discrimination, Psychological / Q000502:physiology; D005260:Female; D005500:Follow-Up Studies; D007839:Functional Laterality / Q000502:physiology; D006309:Hearing / Q000502:physiology*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009622:Noise / Q000009:adverse effects*; D011446:Prospective Studies; D013067:Speech Perception / Q000502:physiology; D016896:Treatment Outcome