Cochlear implantation in unilateral hearing loss: impact of short- to medium-term auditory deprivation

Abstract

Introduction: Single sided deafness (SSD) results in profound cortical reorganization that presents clinically with a significant impact on sound localization and speech comprehension. Cochlear implantation (CI) has been approved for two manufacturers' devices in the United States to restore bilateral function in SSD patients with up to 10 years of auditory deprivation. However, there is great variability in auditory performance and it remains unclear how auditory deprivation affects CI benefits within this 10-year window. This prospective study explores how measured auditory performance relates to real-world experience and device use in a cohort of SSD-CI subjects who have between 0 and 10 years of auditory deprivation.

Methods: Subjects were assessed before implantation and 3-, 6-, and 12-months post-CI activation via Consonant-Nucleus-Consonant (CNC) word recognition and Arizona Biomedical Institute (AzBio) sentence recognition in varying spatial speech and noise presentations that simulate head shadow, squelch, and summation effects (S₀N₀, S_SSDN_NH, S_NHN_SSD; 0 = front, SSD = impacted ear, NH = normal hearing ear). Patient-centered assessments were performed using Tinnitus Handicap Inventory (THI), Spatial Hearing Questionnaire (SHQ), and Health Utility Index Mark 3 (HUI3). Device use data was acquired from manufacturer software. Further subgroup analysis was performed on data stratified by <5 years and 5-10 years duration of deafness.

Results: In the SSD ear, median (IQR) CNC word scores pre-implant and at 3-, 6-, and 12-months post-implant were 0% (0-0%), 24% (8-44%), 28% (4-44%), and 18% (7-33%), respectively. At 6 months post-activation, AzBio scores in S₀N₀ and S_SSDN_NH configurations (n = 25) demonstrated statistically significant increases in performance by 5% (p = 0.03) and 20% (p = 0.005), respectively. The median HUI3 score was 0.56 pre-implant, lower than scores for common conditions such as anxiety (0.68) and diabetes (0.77), and comparable to stroke (0.58). Scores improved to 0.83 (0.71-0.91) by 3 months post-activation. These audiologic and subjective benefits were observed even in patients with longer durations of deafness.

Discussion: By merging CI-associated changes in objective and patient-centered measures of auditory function, our findings implicate central mechanisms of auditory compensation and adaptation critical in auditory performance after SSD-CI and quantify the extent to which they affect the real-world experience reported by individuals.

Keywords: auditory deprivation; cochlear implant; health utility; single-sided deafness; spatial hearing; speech perception.

Figure 1

SSD patients at baseline; NH, normal hearing ear; SSD, impacted ear. (A) Baseline audiogram (B) Word recognition scores (NU-6). Data presented as mean ± 1 SD.

Figure 2

CNC word scores over time; red represents median (IQR) CNC word recognition scores over time. *p < 0.05; **p < 0.01; ***p < 0.001.

Figure 3

AzBio sentence recognition scores over time stratified by duration of deafness (<5 years, 5–10 years) prior to implantation. (A) S₀N₀: speech and noise projected from in front of the subject. (B) S_SSDN_NH: speech projected toward the SSD ear and noise toward the normal ear. (C) S_NHN_SSD: speech projected toward the normal ear and noise toward SSD ear; NH, normal hearing ear (green check); SSD, impacted ear (red “X”). *p < 0.05; **p < 0.01; ***p < 0.001.

Figure 4

Spatial Hearing Questionnaire (SHQ) scores to assess subjective spatial hearing experiences over time stratified by duration of deafness (<5 years, 5–10 years) prior to implantation. (A) Overall aggregate SHQ scores. (B) SHQ scores in speech-in-quiet scenarios. (C) SHQ scores in scenarios where speech and noise are both projected from in front of the subject. (D) SHQ scores in scenarios where speech and noise are separated. *p < 0.05; **p < 0.01; ***p < 0.001.

Figure 5

Health Utility Index Mark 3 (HUI3) scores to assess health-related quality of life over time stratified by duration of deafness (< 5 years, 5–10 years) prior to implantation. (A) Overall HUI3 multi-attribute utility scores (B) HUI3 single-attribute hearing scores (C) HUI3 single-attribute emotion utility scores (D) HUI3 single-attribute pain utility scores (E) HUI3 multi-attribute utility scores for major common debilitating conditions and at baseline for SSD patients. *p < 0.05; **p < 0.01; ***p < 0.001.

Figure 6

Device use data over time stratified by duration of deafness (<5 years, 5–10 years).