Simultaneous Bilateral Cochlear Implantation in Adults: A Multicenter Clinical Study

Abstract

Objective-To determine the efficacy of "simultaneous" bilateral cochlear implantation (both implants placed during a single surgical procedure) by comparing bilateral and unilateral implant use in a large number of adult subjects tested at multiple sites.Design-Prospective study of 37 adults with postlinguistic onset of bilateral, severe to profound sensorineural hearing loss. Performance with the bilateral cochlear implants, using the same speech processor type and speech processing strategy, was compared with performance using the left implant alone and the right implant alone. Speech understanding in quiet (CNCs and HINT sentences) and in noise (BKB-SIN Test) were evaluated at several postactivation time intervals, with speech presented at 0° azimuth, and noise at either 0°, 90° right, or 90° left in the horizontal plane. APHAB questionnaire data were collected after each subject underwent a 3-wk "bilateral deprivation" period, during which they wore only the speech processor that produced the best score during unilateral testing, and also after a period of listening again with the bilateral implants.Results-By 6-mo postactivation, a significant advantage for speech understanding in quiet was found in the bilateral listening mode compared with either unilateral listening modes. For speech understanding in noise, the largest and most robust bilateral benefit was when the subject was able to take advantage of the head shadow effect; i.e., results were significantly better for bilateral listening compared with the unilateral condition when the ear opposite to the side of the noise was added to create the bilateral condition. This bilateral benefit was seen on at least one of the two unilateral ear comparisons for nearly all (32/34) subjects. Bilateral benefit was also found for a few subjects in spatial configurations that evaluated binaural redundancy and binaural squelch effects. A subgroup of subjects who had asymmetrical unilateral implant performances were, overall, similar in performance to subjects with symmetrical hearing. The questionnaire data indicated that bilateral users perceive their own performance to be better with bilateral cochlear implants than when using a single device.Conclusions-Findings with a large patient group are in agreement with previous reports on smaller groups, showing that, overall, bilateral implantation offers the majority of patients advantages when listening in simulated adverse conditions. Persons with bilateral severe to profound sensorineural hearing loss have traditionally received a single cochlear implant. To date, health care professionals have recommended unilateral, rather than bilateral, cochlear implant fittings for these patients for several reasons, including: 1) cost/reimbursement issues, 2) preservation of one ear for future technologies, 3) additional risk of two, or extended, surgeries, and 4) lack of sufficient objective and/or subjective evidence documenting bilateral cochlear implant benefit. Although unilateral use of cochlear implants NIH-PA A...

Cochlear implants: A remarkable past and a brilliant future

“…In particular, bilateral stimulation can provide a substantial benefit in recognizing difficult speech materials such as monosyllabic words and in recognizing speech presented in competition with spatially distinct noise, in comparison to scores obtained with either unilateral implant alone (e.g., Gantz et al, 2002;Müller et al, 2002;Laszig et al, 2004;Ramsden et al, 2005;Litovsky et al, 2006;Ricketts et al, 2006). In addition, use of both implants supports an improved ability to lateralize or localize sounds (depending on which was measured in a particular study), again compared with either unilateral implant (e.g., van Hoesel and Tyler, 2003;Nopp et al, 2004;Senn et al, 2005;Grantham et al, 2007;Tyler et al, 2007).…”

Congenital and Prolonged Adult-Onset Deafness Cause Distinct Degradations in Neural ITD Coding with Bilateral Cochlear Implants

“…As yet, this promise has been only incompletely realized. Current benefits in sound localization are based primarily on interaural level difference (ILD) cues (van Hoesel 2004;Seeber and Fastl 2008;Aronoff et al 2010) and improvements in speech understanding in noise largely result from attending to the ear with the best signal-to-noise ratio (van Hoesel and Tyler 2003;Schleich et al 2004;Litovsky et al 2006). Importantly, bilateral CI users receive minimal benefit from interaural time difference (ITD) cues (van Hoesel 2012), which provide the greatest benefit to normal-hearing listeners in everyday situations (Bronkhorst and Plomp 1992;Zurek 1992;Macpherson and Middlebrooks 2002).…”

Neural and Behavioral Sensitivity to Interaural Time Differences Using Amplitude Modulated Tones with Mismatched Carrier Frequencies

“…Some patients have therefore been implanted bilaterally in the hope of providing the advantages of binaural hearing. Although an important advantage associated with binaural hearing results from differences in the signal-to-noise ratio at each side of the listener, also known as the headshadow or better-ear effect (e.g., Muller et al 2002;Litovsky et al 2004Litovsky et al , 2006, other advantages arise from true binaural interaction. The main binaural cues are interaural intensity differences (IIDs) and interaural time differences (ITDs).…”