Auditory Abilities After Cochlear Implantation in Adults With Unilateral Deafness

Abstract

Objective This pilot study examined speech recognition, localization, temporal and spectral discrimination and subjective reports of cochlear implant (CI) recipients with unilateral deafness. Study Design Three adult males with short-term unilateral deafness (< 5 years) participated. All had sudden onset of severe to profound hearing loss in one ear, which then received a CI, and normal or near normal hearing in the other ear. Speech recognition in quiet and noise, localization, discrimination of temporal and spectral cues and a subjective questionnaire were obtained over several days. Listening conditions were CI, normal hearing (NH) ear, and bilaterally (CI and NH). Results All participants had open-set speech recognition and excellent audibility (250–6000 Hz) with the CI. Localization improved bilaterally compared to the NH ear alone. Word recognition in noise was significantly better bilaterally than with the NH ear for two participants. Sentence recognition in various noise conditions did not show significant bilateral improvement; however, the CI did not hinder performance in noise even when noise was toward the CI side. The addition of the CI improved temporal difference discrimination for two participants and spectral difference discrimination for all participants. Participants wore the CI full time and subjective reports were positive. Conclusion Overall, the CI recipients with unilateral deafness obtained open-set speech recognition, improved localization, improved word recognition in noise, and improved perception of their ability to hear in everyday life. A larger study is warranted to further quantify the benefits and limitations of cochlear implantation in individuals with unilateral deafness.

Strengthening of Hearing Ear Representation Reduces Binaural Sensitivity in Early Single-Sided Deafness

“…Both auditory brainstem response and EEG studies on sequentially implanted children confirmed such an effect with objective measures [Sharma et al, 2005;Gordon et al, 2011Gordon et al, , 2013. Similarly with respect to localisation performance, early single-sided deafness after cochlear implantation shows a smaller benefit compared to postlingual onset [Firszt et al, 2012b].…”

Cochlear Implantation in Children with Single-Sided Deafness: Does Aetiology and Duration of Deafness Matter?

“…In SSD adults, several studies demonstrated improvements in qualities supporting higher-level processing and integration of both acoustic and electrical signals leading to improved overall hearing. The improvements in performance reported for younger CI patients with acquired SSD suggest that results were equivalent to those seen for SSD adults and show evidence of rehabilitation of binaural hearing and similar improvement in the quality of speech comprehension in noise and the ability for sound localisation [Arndt et al, 2011a, b;Punte et al, 2011;Stelzig et al, 2011;Firszt et al, 2012;Plontke et al, 2013].…”

Cochlear Implants in Single-Sided Deafness

“…Despite this increase in cochlear function of the SSD ear, the binaural benefits of free-field speech comprehension gleaned after implantation are limited in quiet environments, likely because the normal hearing ear doesn't need to rely on binaural squelch and summation when noise is not present. In a case series with 3 subjects implanted for SSD, Firszt et al reported only 1 patient who showed statistically significant improvements in CNC speech scores in the bimodal, quiet condition compared to either unilateral NH or CI-alone conditions [8]. In the same study, adding noise to the speech tests resulted in 2/3 patients showing significantly better CNC scores in the bilateral condition than solely with either the normal hearing ear alone.…”

“…Additionally, patients with CIs performed significantly better with their CI when localizing than in unaided, CROS, and Baha conditions [10]. In a case series of 3 patients, Firszt et al demonstrated improvements in localization in 10°i ncrements when sound was presented to the CI ear, NH ear, and bilaterally [8].…”

“…It is now widely known that individuals with SSD face significant challenges to hearing in complex or noisy environments and in localizing or lateralizing sound sources [6 • ]. Not surprisingly, individuals who suffer from SSD consistently rate lower in quality of life inventories such as the speech, spatial, and qualities hearing scale (SSQ) [7][8][9][10]. Deficiencies in speech comprehension are chiefly a result of impaired binaural squelch and summation, whereas deficiencies in azimuth localization are mostly due to impaired calculation of interaural phase differences (IPDs), time differences, and intensity differences [6 • , 7, 10, 11 •• ].…”