Hearing-in-Noise Benefits After Bilateral Simultaneous Cochlear Implantation Continue to Improve 4 Years After Implantation

Abstract

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. Design 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), 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. Conclusion 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.

Speech-perception-in-noise and bilateral spatial abilities in adults with delayed sequential cochlear implantation

“…The results correspond with previous reports on bilateral sequential and simultaneous adult CI users that demonstrated a summation benefit of up to 6 dB and/or no effect or negative effects (Litovsky et al, 2006;Wolfe et al, 2007;Eapen et al, 2009;Van Deun et al, 2010).…”

“…The squelch effect in general is small even in normal-hearing listeners where it is in the order of 3 dB (Eapen et al, 2009). It has been reported in only a few previous studies investigating bilateral benefit in adult CI users (Laszig et al, 2004;Eapen et al, 2009).…”

“…The median squelch effect for both CI 1 and CI 2 (0 dB and 1 dB, respectively) was within the accepted range of ≤2 dB (Laszig et al, 2004;Litovsky et al, 2006;Van Deun et al, 2010) on a 5% level of significance. The median summation benefits for both CI 1 (0 dB) and CI 2 (2 dB) added to BiCI in the NF condition was within the accepted value range of ≤6 dB (Litovsky et al, 2006;Wolfe et al, 2007;Eapen, Buss, Adunka, Pillsbury & Buchman, 2009;Van Deun et al, 2010) at the 5% level of significance. The median SRM benefit values were within the accepted range of 0 to 4 dB (Litovsky et al, 2006;Van Deun et al, 2010) only when the noise was directed to CI 1 at the 5% level of significance.…”

“…It has been reported in only a few previous studies investigating bilateral benefit in adult CI users (Laszig et al, 2004;Eapen et al, 2009). Current reports demonstrate a benefit of 2 dB and even zero or negative effects in sequentially and simultaneously implanted adults (Laszig et al, 2004;Litovsky et al, 2006;Van Deun et al, 2010).…”

“…The concurrent stimulation of both peripheral and central auditory systems may lead to improved interaction between the ipsi-and contralateral auditory pathways and provide more robust processing of signals (Manrique et al, 2007). Simultaneously implanted listeners required an SNR of at least 6.8 dB to achieve speech perception after 1 year, decreasing to 1.8 dB after 4 years of bilateral simultaneous implantation (Eapen et al, 2009). The latter SNR is significantly lower than the SNR values recorded for delayed sequentially implanted adults in this study (average SNR: 18.83 dB) despite most participants (6/11) having had bilateral experience of more than 4 years ( Table 2).…”