Consonant and vowel confusions in well-performing adult cochlear implant users, measured with a nonsense syllable repetition test.

OBJECTIVE: The study's objective was to identify consonant and vowel confusions in cochlear implant (CI) users, using a nonsense syllable repetition test. DESIGN: In this cross-sectional study, participants repeated recorded mono- and bisyllabic nonsense words and real-word monosyllables in an open-set design. STUDY SAMPLE: Twenty-eight Norwegian-speaking, well-performing adult CI users (13 unilateral and 15 bilateral), using implants from Cochlear, Med-El and Advanced Bionics, and a reference group of 20 listeners with normal hearing participated. RESULTS: For the CI users, consonants were confused more often than vowels (58% versus 71% correct). Voiced consonants were confused more often than unvoiced (54% versus 64% correct). Voiced stops were often repeated as unvoiced, whereas unvoiced stops were never repeated as voiced. The nasals were repeated correctly in one third of the cases and confused with other nasals in one third of the cases. The real-word monosyllable score was significantly higher than the nonsense syllable score (76% versus 63% correct). CONCLUSIONS: The study revealed a general devoicing bias for the stops and a high confusion rate of nasals with other nasals, which suggests that the low-frequency coding in CIs is insufficient. Furthermore, the nonsense syllable test exposed more perception errors than the real word test.

Sustained reduction of tinnitus several years after sequential cochlear implantation.

OBJECTIVE: This study aimed to explore the short- and long-term effects of a second cochlear implant (CI-2) on the reduction of tinnitus annoyance and tinnitus handicap. DESIGN: In a combined retrospective and prospective cohort study, tinnitus annoyance was measured before receiving the CI-2 (Pre), more than two years after (Post1) and more than seven years after (Post2), using the Tinnitus Handicap Inventory (THI), the Visual Analog Scale for the assessment of perceived tinnitus loudness (VAS-L) and annoyance (VAS-A), and a self-report questionnaire. STUDY SAMPLE: Twenty sequentially bilaterally implanted adults with bothersome tinnitus. RESULTS: CI-2 implantation resulted in a statistically significant reduction of tinnitus handicap from severe at Pre to mild at Post1 (THI mean score reduced from 61.3 [SD = 19.4] to 29.3 [SD = 23.5]). The reduction in tinnitus annoyance was statistically significant from Pre to Post 2 (VAS-A reduced from 7.1 [SD = 1.5] to 3.4 [SD = 2.2]). The reduction in tinnitus loudness was not statistically significant. CONCLUSIONS: The provision of a CI-2 for severely and profoundly hearing-impaired individuals with bothersome tinnitus is an effective method of providing long-term tinnitus relief.

Sound localising ability in children with bilateral sequential cochlear implants.

OBJECTIVES: To evaluate the sound localisation ability in children with sequential bilateral cochlear implants and the potential influence of age at the time of the first implantation, years of experience with the first implanted ear and the inter-implant interval (time between the first and the second cochlear implantation). METHODS: Sixty-three prelingually deaf children (mean age, 11.03; range, 6.5-17 years; SD, 3.09) were tested after 12 and 24 months of using bilateral cochlear implants. Every child was tested with each ear alone and both ears together. Five loudspeakers were placed in a 180° horizontal arch with 45° of separation between each loudspeaker. The child was placed 1.5m from the speakers. For each test run, three stimuli were presented at 65dB (A) from each speaker for a total of 15 stimulus presentations. For each test run, we calculated the mean angular error (MAE) and the proportion of correct speakers identified (CSS: correct speaker score). Performance by chance for the MAE was 72° and for the CSS was 20% (1 of 5 speakers). RESULTS: After 12 months of using bilateral CIs, the added effect of the second CI in the MAE was minor, and there was no significant difference in CSS between listening in the unilateral condition and listening in bilateral condition. After 24 months, however, the added effect of the second CI in the MAE was significant (mean diff=12.2°; 95% CI; 4.5-20.0°, p=0.003). The mean bilateral CSS increased significantly to 38% (diff=7.7%; 95% CI; 1.4-14.0%; p=0.019) while the mean unilateral CSS remained at a similar level (27%). The influence of age at the time of the first implantation on CSS after 24 months was not significant (p=0.96). However, the inter-implant interval showed a significant decrease in score by 1.4% per year between the two implants (p=0.04). CONCLUSION: Sound localisation with two versus one CI in children with a sequential bilateral cochlear implantation was significantly improved 24 months (but not 12 months) after the second implantation. A shorter inter-implant interval showed a small but significant beneficial effect on sound localisation.

Perception and confusion of speech sounds by adults with a cochlear implant.

The aim of this pilot study was to identify the most common speech sound confusions of 5 Norwegian cochlear implanted post-lingually deafened adults. We played recorded nonwords, aCa, iCi and bVb, to our informants, asked them to repeat what they heard, recorded their repetitions and transcribed these phonetically. We arranged the collected data in confusion matrices to find the most common and most uncommon speech sound confusions. We found that the voiced and unvoiced consonants are seldom confused. We also found that there was a higher rate of consonant confusion for the iCi words than for the aCa words. The most frequent confusion was [eta] perceived as [n], [m] perceived as [n] and [upsilon] perceived as [n]. For the consonants, manner of articulation was rarely confused, but place of articulation was often confused. An exception from this was the confusion of [l] and [n], which differs only in manner of articulation. The latter is in accordance with reports we get from clinicians. We postulate that this is caused by the speech processing of the cochlear implant. We found less confusion of the vowels, which can be explained by the fact that vowels have much higher energy and longer duration than most of the consonants. The most frequent confusion was [a:] perceived as [see text] and [u:] perceived as [see text]. [e:], [i:] and [see text] were never confused with other vowels.