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.
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.
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.
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.
Efficacy of simultaneous bilateral cochlear implants was studied in 37 postlinguistically deaf adult recipients of N24 devices. Speech understanding in quiet and in noise were evaluated, and measures were obtained using the APHAB questionnaire. By 6-mo postactivation a significant advantage of bilateral listening was seen, primarily for the head-shadow effect, with some benefits due to binaural summation and squelch. Subjects fell into groups with asymmetrical or symmetrical bilateral performance, not predicted from pre-implantation performance. Results from this large, multicenter study suggest that adults with postlinguistic deafness are likely to demonstrate objective and subjective benefits when hearing with both ears.
University of Wisconsin, Madison, Wisconsin (R.L.); Cochlear Americas, Englewood, Colorado (A.P., J.A.); University of Colorado, Boulder, Colorado (C.S.).
Address for correspondence: Ruth Litovsky, University of Wisconsin, Waisman Center, Room 521, 1500 Highland Avenue, Madison WI 53705. E-mail: firstname.lastname@example.org.
Received January 14, 2005; accepted May 28, 2006.