Multicenter U.S. bilateral MED-EL cochlear implantation study: speech perception over the first year of use.
OBJECTIVE
Binaural hearing has been shown to support better speech perception in normal-hearing listeners than can be achieved with monaural stimulus presentation, particularly under noisy listening conditions. The purpose of this study was to evaluate whether bilateral electrical stimulation could confer similar benefits for cochlear implant listeners.


METHODS
A total of 26 postlingually deafened adult patients with short duration of deafness were implanted at five centers and followed up for 1 yr. Subjects received MED-EL COMBI 40+ devices bilaterally; in all but one case, implantation was performed in a single-stage surgery. Speech perception testing included CNC words in quiet and CUNY sentences in noise. Target speech was presented at the midline (0 degrees), and masking noise, when present, was presented at one of three simulated source locations along the azimuth (-90, 0, and +90 degrees).


RESULTS
Benefits of bilateral electrical stimulation were observed under conditions in which the speech and masker were spatially coincident and conditions in which they were spatially separated. Both the "head shadow" and "summation" effects were evident from the outset. Benefits consistent with "binaural squelch" were not reliably observed until 1 yr after implantation.


CONCLUSIONS
These results support a growing consensus that bilateral implantation provides functional benefits beyond those of unilateral implantation. Longitudinal data suggest that some aspects of binaural processing continue to develop up to 1 yr after implantation. The squelch effect, often reported as absent or rare in previous studies of bilateral cochlear implantation, was present for most subjects at the 1 yr measurement interval.
Buss
Emily
E
Department of Otolaryngology/Head and Neck Surgery, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA. ebuss@med.unc.edu
Pillsbury
Harold C
HC
Buchman
Craig A
CA
Pillsbury
Carol H
CH
Clark
Marcia S
MS
Haynes
David S
DS
Labadie
Robert F
RF
Amberg
Susan
S
Roland
Peter S
PS
Kruger
Pamela
P
Novak
Michael A
MA
Wirth
Julie A
JA
Black
Jennifer M
JM
Peters
Robert
R
Lake
Jennifer
J
Wackym
P Ashley
PA
Firszt
Jill B
JB
Wilson
Blake S
BS
Lawson
Dewey T
DT
Schatzer
Reinhold
R
D'Haese
Patrick S C
PS
Barco
Amy L
AL
D000328:Adult; D000368:Aged; D019929:Cochlear Implantation; D003638:Deafness / Q000601:surgery*; D004558:Electric Stimulation / Q000295:instrumentation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013067:Speech Perception / Q000502:physiology*; D013997:Time Factors; D014825:Vocabulary