KEY POINTS
- Cochlear implant effectiveness in asymmetric hearing loss and
single-sided deafness is well established, but rarely covered by
health care systems.
- Continuation of wearing the implant beyond the first year could be
considered as an indirect indicator of subjective benefit.
- Percentage of cochlear implant abandon at 5-years post-implantation
was very low in patients with asymmetric hearing loss and single-sided
deafness.
- High education level, low audibility and good unaided speech
perceptions scores of the contralateral acoustic-hearing ear were
positive prognostic factors of CI use.
- The low percentage of non-users is an additional strong argument to
recommend cochlear implantation in patients with asymmetric hearing
loss and single-sided deafness, on the ear with a profound hearing
loss, especially in case of frail contralateral acoustic-hearing ear.
INTRODUCTION
The effectiveness of cochlear implantation in case of asymmetric hearing
loss (AHL) and single-sided deafness (SSD) was well established in
several studies with a short-term (~1-year) follow-up.
By restoring binaural information, cochlear implant (CI) improves speech
recognition in noisy environment, localization of sound sources, quality
of life, and reduces cognitive load and incapacitating tinnitus for most
patients. However, cochlear implantation in SSD and AHL is rarely
covered by health care systems around the world, only in case of
incapacitating tinnitus in some countries. CI use over time would be
another indicator of subjective benefit, but was rarely reported (1–3).
Furthermore, most studies included AHL patients with sensorineural
hearing loss criteria of unaided mean pure-tone average (PTA). The aim
of our study was to evaluate the CI use in AHL and SSD with a follow-up
of 5 years, and to look for reasons of abandonment. AHL candidates were
patients with bilateral sensorineural or mixed severe-to-profound
hearing loss on PTA, but asymmetrical aided speech perception scores
(SPS).
METHODS
Study design
This was a retrospective single-center cohort study.
Participants
Patients were selected from the database of postlingually deafened
adults who underwent a unilateral cochlear implantation from September
2011 to December 2018 in a referent tertiary center. Patients included
had a severe-to-profound hearing loss on the ear to be implanted, with a
PTA≤70 dB (0.5, 1, 2, and 4 kHz) and an aided SPS<50% for
disyllabic words at 60 dB SPL. SSD candidates had a PTA≤30 dB and a
SPS≥90% on the acoustic-hearing ear. AHL candidates had an aided
SPS≥60% for disyllabic words on the acoustic-hearing ear, and an
interaural SPS gap≥40%. Patients were excluded in case of fluctuating
hearing loss, surgical complication, device failure, reimplantation, or
severe psychiatric problem during the first year after the cochlear
implantation. Implant devices of the four companies were used. Written
informed consent was obtained from patients (CNIL N°2126598).
Data including age, sex, education level, work situation, duration and
etiology of hearing loss, hearing aid use and brand of the CI device
were recorded. In case of lost to follow-up (n=6), patient was contacted
to find out why and how long they were no longer wearing the implant.
Hearing ability was evaluated before and 1, 3 and 5 years after
implantation. PTA and unaided speech recognition using disyllabic words
(Fournier lists) were tested with headphones at 60 dB SPL. Speech
recognition in best-aided conditions was tested in free-field at 60 dB
SPL, for the implanted ear (with contralateral ear masking), the
acoustic-hearing ear, and in bimodal conditions using mono- (Lafon
lists) and disyllabic words in quiet, and sentences (Marginal Benefit
for Acoustic Amplification lists) in noise at a signal-to-noise ratio of
+10 dB, signal and noise in front of the patient. Subjective evaluation
of communication in noise was evaluated using the Abbreviated Profile of
Hearing Aid Benefit (APHAB) questionnaire.
Statistical analysis was performed using GraphPad
Prism (Version 9.4.0). Values were expressed as mean
± standard deviation. Unpaired t-tests or mixed-effect analysis with a
Tukey post-test were used for quantitative data, and Fisher’s test for
qualitative data. Significance was defined at a level of
p<0.05.
Demographic data and audiometric evaluation of 72 patients (66 AHL, 6
SSD) are reported in Table 1. The mean follow up was 3 ± 1.8 years
[1-7]. Only three AHL candidates did not use a hearing aid on the
acoustic-hearing ear: two cases with mild hearing loss (PTA: 33 and 35
dB, respectively) and one vestibular schwannoma.
At 1-year post-implantation, 71 patients (97%) still used their CI all
day long, only one patient became non-user due to the lack of subjective
benefit (Figure 1). Of the 66 patients implanted for 3 years, 61 (92%)
used their CI all day long. One patient aged 86-years at time of
implantation deceased. One patient with a partial extrusion of the
electrode array, refused the revision surgery and stopped to use the CI.
Three patients became non-users due to the lack of subjective benefit.
Of the 44 patients implanted for 5 years, 42 (95%) used their CI all
day long. One patient aged 82-years at time of implantation deceased,
and one patient became non-user due to the lack of subjective benefit.
In total, among the 72 patients, 42 used their implant at 5-years, 22
had a follow-up <5-years, 2 deceased, 1 had electrode
extrusion, and 5 patients became non-users. For these 5 patients, 2 AHL
patients had a no objective benefit (at 1- and 3-years after
implantation), 2 SSD patients had no subjective benefit with SPS at 50
and 100% for disyllabic words at 1-year, and no reasons to explain the
abandon, 1 AHL patient became non-user at 1-year, and refused to be
tested.
Compared to users (Table 2), the non-users had a lower education level(p<0.05), a lower PTA (p<0.01 ), and a
higher unaided SPS of the acoustic-hearing ear
(p<0.05 ). Aided SPS for disyllabic words for the
acoustic-hearing ear, and in bimodal condition were similar between
users and non-users.
Considering the evolution of the auditory performance in cochlear
implant users, aided SPS of the implanted ear improved at 1-year
post-implantation compared to pre-implantation scores in quiet, for both
disyllabic (68 ± 31.9% vs 14 ± 18.2%,p<0.0001, Figure 2A) and monosyllabic words (57
± 27.2% vs 13 ± 18.4 % respectively,p<0.0001 ), and sentences in noise (57 ± 30.9%vs 7 ± 14.7%, p<0.0001 ). These scores remained
stable at 3- and 5-years post-implantation. For the acoustic-hearing
ear, the PTA remained stable (data not shown). However, the unaided SPS
for disyllabic words decreased (p<0.05, Figure
2B), but the aided SPS remained stable over time (disyllabic and
monosyllabic words in quiet, sentences in noise, data not shown). In
bimodal condition, aided SPS improved after implantation and remained
stable between 1- and 5-years in both quiet (data not shown) and noise
(Figure 2C).
The total APHAB score decreased at 1-year post-implantation compared to
preoperative scores, (48 ± 16.8% vs 63 ± 17.2%,p<0.0001) , showing an improvement of the communication
in noise, and then remained stable at 3- and 5-years post-implantation
(data not shown).
DISCUSSION
This study shows a small rate of non-users at 1-year post-implantation
among post-lingually deaf adults CI recipients (1.4 %), a percentage
similar to that reported in the literature (4,5). At 5-years
post-implantation, 4 out of the 6 patients with SSD still used their CI
(67%). Among the 66 AHL patients with follow-up over 1 year, 2 patients
abandoned the CI use and one refused revision surgery. Among the 40 AHL
patients with a 5-years follow-up, only one patient became non-user (2.5
%). In the literature, after the first year post-implantation, the
percentage of non-users varies among studies: 10% at 2-years post-
implantation among 20 SSD patients (3), 4.4% among 114 SSD patients
with a follow-up of 1.5 to 60 months (2), 9.8 % among 41 SSD and 0%
among 37 AHL patients with a follow-up of 6 to 11 years (1), 19% among
28 SSD and AHL patients with a follow-up of 45 to 67 months (6). The
reported main reasons of non-use were lack of perceived benefit, as in
our study, and unrealistic expectations. It should be noticed that the
long-term non-user rate in CI recipients for post-lingually bilateral
profound deafness was in the same range (7.5 to 11%) than in SSD/AHL
patients (2).
In our study, the risk factors of discontinuation of CI use were mainly
a good unaided acoustic-hearing ear, but also a low education level.
In France, cochlear implantation was recommended only in case of
bilateral severe-to-profound hearing loss, but SSD/AHL with
incapacitating tinnitus has been added to the criteria since September
2021. However, some CI centers have added other off-label indications
(7). Most patients included in our study have been implanted because of
an identified ear disease, with a risk of progressive decrease of speech
intelligibility of the acoustic-hearing ear. Thus, only 32% of our
patients were implanted for an unknown etiology, whereas the unknown
etiology is most common in cohort of adult CI recipients (8). It was
decided to implant the ear with the profound hearing loss to avoid a
long duration of hearing deprivation, and a long period with high
listening effort and poor quality of life, and cognitive decline in
older patients. The improvement of speech intelligibility in quiet and
noise and of the subjective benefit in noise, on tests performed in
routine practice, are in accordance with all prospective trials
(4,9,10).
Due to the retrospective analysis, evaluation of severity of tinnitus
using a self-assessment scale that could influence the wearing of the
CI, was missing for many patients, so this variable was not analyzed.
Datalogging was also not available for all brands.