10.14639/0392-100X-N1146
Objectives. The aim of present study is to evaluate the impact of prognostic factors on the outcome in a group of prelingually hearing-impaired patients submitted to cochlear implantation (CI) at an adult age.Methods. This is a retrospective study on a cohort of prelingually severe-to-profound hearing- impaired patients cochlear implanted in adulthood and followed by a single audiology centre. We correlated post-CI results in term of speech perception with patients’ speech perception with hearing aids before implantation, history of progression of hearing loss (HL), and levels of education and cognition. The study group was composed of 49 patients.Results. Post-CI open-set recognition score in silence and noise was significantly correlated with pre-CI open-set recognition score in silence and with background noise. Patients with a history of progression of HL gained significantly better results. Furthermore, we found higher improvements in patients with a higher level of education.Conclusions. Prelingually deafened patients implanted in adulthood achieved satisfactory results. Significantly better results were achieved by patients with better pre-operative speech perception scores, progressive HL and higher level of education.
application/xml
1827-675X
1146
en
Stefano Berrettini
https://creativecommons.org/licenses/by-nc-nd/4.0
ACTA Otorhinolaryngologica Italica
educational achievement
Cochlear implant in prelingually hearing-impaired adults: prognostic factors and results
Text.Serial.Journal
https://www.actaitalica.it/
41
Audiology
2021-05-05
2020-09-29
2021-05-17
2021-05-17
173-179
1
Stefano Berrettini
2021/05/05
10.14639/0392-100X-N1146
173
Otolaryngology, Audiology and Phoniatrics Unit, University of Pisa, Pisa, Italy; 2 Section of Statistics, University Hospital of Pisa, Italy; Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
1827-675X
educational achievement
179
Cochlear implant in prelingually hearing-impaired adults: prognostic factors and results
https://www.actaitalica.it/article/download/1146/548
41
ACTA OTORHINOLARYNGOLOGICA ITALICA 2021;41:173-179; doi: 10.14639/0392-100X-N1146




Audiology


Cochlear implant in prelingually hearing-impaired
adults: prognostic factors and results
L’impianto cocleare nei pazienti adulti con sordità prelinguale: fattori prognostici
e risultati
Francesca Forli1, Francesco Lazzerini1, Valentina Montecchiari1, Riccardo Morganti2, Luca Bruschini1,
Stefano Berrettini1,3
1
  Otolaryngology, Audiology and Phoniatrics Unit, University of Pisa, Pisa, Italy; 2 Section of Statistics, University Hospital of Pisa,
Italy; 3 Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden


SUMMARY
Objectives. The aim of present study is to evaluate the impact of prognostic factors on the
outcome in a group of prelingually hearing-impaired patients submitted to cochlear implan-
tation (CI) at an adult age.
Methods. This is a retrospective study on a cohort of prelingually severe-to-profound hear-
ing-impaired patients cochlear implanted in adulthood and followed by a single audiology
centre. We correlated post-CI results in term of speech perception with patients’ speech
perception with hearing aids before implantation, history of progression of hearing loss
(HL), and levels of education and cognition. The study group was composed of 49 patients.
Results. Post-CI open-set recognition score in silence and noise was significantly corre-
lated with pre-CI open-set recognition score in silence and with background noise. Patients
with a history of progression of HL gained significantly better results. Furthermore, we
found higher improvements in patients with a higher level of education.                           Received: September 29, 2020
Conclusions. Prelingually deafened patients implanted in adulthood achieved satisfac-             Accepted: November 27, 2020
tory results. Significantly better results were achieved by patients with better pre-operative
speech perception scores, progressive HL and higher level of education.                           Correspondence
                                                                                                  Francesca Forli
KEY WORDS: prelingual deafness, cochlear implant, cognitive aspects, speech perception,           ENT Audiology and Phoniatrics Unit, Pisa Univer-
educational achievement                                                                           sity Hospital, via Paradisa 2, 56120 Pisa, Italy
                                                                                                  E-mail: francesca.forli@gmail.com
RIASSUNTO
Obiettivo. L’obiettivo di questo studio è valutare l’impatto di alcuni fattori prognostici        Funding
                                                                                                  None.
sui risultati post impianto cocleare in un gruppo di pazienti affetti da sordità prelinguale
sottoposti ad impianto cocleare (IC) in età adulta.
Metodi. È stato fatto uno studio retrospettivo su una coorte di pazienti con sordità prelin-      Conflict of interest
                                                                                                  The Authors declare no conflict of interest.
guale sottoposti a IC e seguiti da un unico centro impianti cocleari, andando ad analizzare
i risultati post-impianto in termini di percezione verbale e correlando questi risultati alle
capacità di discriminazione verbale pre-impianto, la presenza di una sordità prelinguale            How to cite this article: Forli F, Lazzer-
ma ad andamento progressivo, i livelli cognitivi e di istruzione.                                   ini F, Montecchiari V, et al. Cochlear im-
Risultati. I risultati percettivi post-IC sono stati significativamente correlati con le capa-      plant in prelingually hearing-impaired adults:
cità di percezione verbale pre-IC; inoltre, migliori risultati sono stati ottenuti dai pazienti     prognostic factors and results. Acta Otorhi-
con una storia di sordità progressiva. Infine, un miglioramento significativamente più co-          nolaryngol Ital 2021;41:173-179. https://doi.
                                                                                                    org/10.14639/0392-100X-N1146
spicuo si è verificato nei pazienti più scolarizzati.
Conclusioni. I pazienti con sordità prelinguale impiantati in età adulta possono raggiun-
                                                                                                  © Società Italiana di Otorinolaringoiatria
gere buoni risultati in termine di percezione verbale. Migliori risultati sono ottenibili nei     e Chirurgia Cervico-Facciale
pazienti con storia di progressione della sordità, buone abilità percettive pre-IC, buon li-
vello di scolarizzazione.                                                                                        OPEN ACCESS
PAROLE CHIAVE: sordità prelinguale, impianto cocleare, aspetti cognitivi, percezione              This is an open access article distributed in accordance with
verbale, livelli educativi                                                                        the CC-BY-NC-ND (Creative Commons Attribution-Non-
                                                                                                  Commercial-NoDerivatives 4.0 International) license. The
                                                                                                  article can be used by giving appropriate credit and mentio-
                                                                                                  ning the license, but only for non-commercial purposes and
                                                                                                  only in the original version. For further information: https://
                                                                                                  creativecommons.org/licenses/by-nc-nd/4.0/deed.en




                                                                                                                                                          173
F. Forli et al.




Introduction                                                       tion should be an important candidacy criterion in cochlear
                                                                   implantation of adult patients with prelingual deafness 1,2,4-6.
Prelingually deafened adult patients who receive a cochlear
                                                                   In addition to the factors previously mentioned, it is well
implant (CI) in adulthood, after many years of severe-to-          known that other pre-operative individual and audiological
profound hearing impairment or auditory deprivation, con-          features play a role in post-operative hearing performance,
stitute a very specific group of cochlear implant users 1-9.       such as age at onset of hearing loss and at first hearing aid
Until the mid-1990s, prelingually deafened adult patients          fitting, speech perception performance with hearing aids,
were considered poor CI candidates because of limited im-          residual hearing, communication mode, educational envi-
provement in speech perception. However, several recent            ronment, motivation and psychological aspects 2,4,6,9,12,13.
studies suggest that the latest implant technology may re-         Moreover, in 2011 Dijkhuizen et al. reported that speech
sult in open-set speech perception abilities and significant       intelligibility is predictive of post-implantation hearing re-
subjective benefits, although variability among individuals        sults in prelingually deafened adults 13,14.
is high and performance generally lags behind that of post-        From this point of view, improving our knowledge on
lingually deafened adults 1,2,10.                                  prognostic factors in this category of patients could help
Nevertheless, cochlear implantation in prelingually deaf-          clinicians to predict the results more precisely and allow
ened adult patients is still a real challenge, since it requires   patients to have realistic expectations.
a difficult decision-making process for both clinicians and        The aim of the present study is to evaluate the impact of
patients, due to the uncertainty of the outcome, the risk of       prognostic factors on outcomes in a group of prelingually
obtaining poor or no improvement in speech perception or           hearing impaired patients submitted to CI in adulthood
that they stop using their CI.                                     at our institution. To do this, we correlated the results
In addition, despite significant improvements in average           achieved in terms of speech perception both in quiet and
performance after implantation in prelingually deafened            with background noise with some of the factors that are
adult patients, there remains a considerable amount of un-         known to positively affect the post-CI results, such as age
predictable inter-subject variability. This wide spectrum of       at first hearing aid fitting, pure tone audiometry with and
results is likely to be related to the wide variability of the     without hearing aids before implantation, speech percep-
characteristics of patients, many of which have a prognos-         tion with hearing aids before implantation and progression
tic role.                                                          of HL. Furthermore, we investigated the possible correla-
When considering potential prognostic factors in early             tion between post-CI results with the level of education and
hearing-impaired adults, it must be underlined that these          cognition of each patient.
patients have some peculiarities since they have never ex-
perienced normal hearing in their lifetime, or since the first
moments of life. Their neural system, therefore, lacks the         Materials and methods
spatial and structural organisation for auditory processing        Since 1998, 75 patients with a prelingual onset of severe
with variability between subjects 2-6,8,9. Furthermore, even       to profound hearing loss have received a CI in adulthood
if it is possible that auditory pathway fiber tracts develop in    at our institution. For the study we enrolled patients with
a limited degree independently of the experience 11, the lit-      a diagnosis of severe-to-profound hearing deficit and first
erature suggests that in the case of severe-to-profound pre-       hearing aid fitting before 4 years of age, who received an
lingual hearing loss, the colonisation of the auditory cortex      oralist rehabilitation during their childhood and who had
by other sensory modalities is the main limiting factor in         been consistently using the hearing aid in the implanted ear
post-implantation performance, and not the pathological de-        before surgery, i.e. morning to bedtime, every day.
generative changes of the auditory nerve, cochlear nucleus,        Among the 75 implanted patients, we enrolled patients who
or auditory midbrain 5,6. Both the above-mentioned condi-          received a unilateral CI in our unit at adult age (16 years
tions must be kept in mind when considering the results af-        or older), who are Italian speakers, had at least 1 year of
ter implantation achievable by pre-lingually deafened adult        follow-up in our clinic and who gave their consent to par-
patients. Moreover, some recent studies have confirmed             ticipate in the study. We excluded patients with neuropsy-
the important role of effective early auditory input on CI         chiatric disorders, cochlear malformations, or incomplete
performance in early deafened adults 4-6. Consequently, the        electrode array insertion. Forty-nine patients were enrolled
educational programmes that stress oral communication as           according to these criteria.
the preferred educational modality could potentially reduce        Local ethical committee approval was obtained.
the cortical colonisation of the central speech and language       We retrospectively reviewed the anamnestic data of all pa-
processing areas, and therefore the use of oral communica-         tients and audiologic results assessed at the last postopera-



174
                                                                                       Cochlear implant in prelingually deafened adults




tive check-up at our centre. Pre-operatively, all patients un-   (25/49) to a cognitive test, the Raven Standard Progressive
derwent comprehensive audiological evaluation, including         Matrices (SPM) 16. This test has been developed for evalu-
a speech perception test 15 without lip-reading with hearing     ation of non-verbal, abstract and cognitive functioning and
aids, neuroradiological evaluation by petrous bone high          is considered the main test for the estimation of “fluid in-
resolution computed tomography (CT) and brain and inner          telligence” (the ability to reason quickly, think abstractly
ear magnetic resonance (MR). The etiology of hearing loss        and problem-solve). Thus, the results are not influenced by
was investigated by molecular analysis of the connexin 26        educational background or by cultural or linguistic defi-
and 30 genes, and mitochondrial DNA A1555G mutation              ciencies.
analysis in all cases, and PDS gene mutation analysis in         We correlated the post-CI open-set speech recognition
patients with a large vestibular aqueduct.                       score both in silence and with background noise with the
Post-operatively, during follow-up visits, all patients were     following personal and audiological characteristics of the
assessed with the CI with pure tone audiometry in free field     patients: age at deafness diagnosis and at first HA fitting,
and with a speech perception test without lip-reading 15.        presence of pre-operatory progression of hearing loss, pre-
Pure-tone audiometry was conducted with an Interacous-           operatory hearing threshold with and without hearing aids,
tics Clinical Audiometer AC40. When measuring the hear-          pre-operatory speech perception score, educational level
ing threshold, both with HA and without HA, we assigned          and results at SPM. Progression was defined as a worsening
a value of 125 dB to any frequency threshold over the max-       > 10 dB in PTA from the diagnosis of HL to pre-operatory
imum output limit of the audiometer (105 dB for 0.25 KHz         evaluation.
and 125 dB for 0.5 and 1 KHz, 120 dB for 2 KHz). Any             For statistical analysis, to compare quantitative variables
vibrotactile sensation was excluded.                             as post-CI open-set recognition score both in silence and
Speech perception was assessed using a speech perception         with background noise (dependent variables) with continu-
test in Italian language 15 before (with HA) and after im-       ous and qualitative variables, Pearson’s correlation analysis
plantation (with CI) in free field by the same speech thera-     and t-test for independent samples (two-tailed) were used,
pist in all the patients to avoid bias, with live voice and      respectively. The significant independent variables were
without lip-reading. We evaluated the disyllabic word rec-       then analysed together by a multivariate model based on
ognition score using lists of 20 Italian words at a level of     a multiple linear regression model. Finally, pre-CI open-
65 dB. Testing the open-set speech recognition score with        set recognition score in silence and with background noise
background noise, we considered a signal-to-noise ratio          was compared with post-CI open-set recognition score in
(SNR) +10. The speech therapist as far as the loudspeaker        silence and with background noise by ANOVA for repeated
for the noise stayed in front of the patients during the tests   measures stratified for educational level. Significance was
(S0N0). Post-operatively, patients that used the CI with         fixed at 0.05. All analyses were performed by SPSS v. 26
a contralateral HA were tested with bimodal stimulation          technology.
(which is the everyday hearing condition).
At the study setup we administered the “University of Pisa
                                                                 Results
Questionnaire” (UPQ) to all patients to obtain information
on personal factors and subjective benefits from CI. This        We report the results of 49 prelingually deafened patients
questionnaire was specifically developed by our research         submitted to CI at adult age at our institution. The charac-
team and consists of a 40-question survey divided into 3         teristics of the cohort are reported in Table I.
sections. In the first, pre-operative information, such as       Twenty-four patients were women, and 25 were men. The
type of hearing aid, ability to have telephone conversations,    mean age at first HA fitting was 2.1 years (1 month to 4
perception of music and rehabilitation are collected; in the     years). The mean age at the cochlear implantation was 33.9
second, the same aspects after implantation are investi-         years (16-60 years).
gated; in the third, information about social life, education    The mean follow-up duration after surgery was 10.4 years,
level and working life are recorded. The questionnaire is        ranging from 1 to 21 years.
available as supplementary material (Appendix 1 - https://       The mean preoperative pure tone threshold in the implanted
www.actaitalica.it/article/view/1146/548).                       ear was 107.3dB (87-> 120dB) and the mean preoperative
We also evaluated the education level of patients by the         free-field threshold with HA was 57.77 dB (37-97dB). The
UPQ, and divided patients into 3 groups based on each            mean preoperative open-set speech recognition score was
individual level achieved: university degree, a high school      14.9% (0-75%) in silence and 0.7% (0-15%) in noise. Only
certificate and a secondary school certificate.                  5/49 (10.2%) were capable of sustaining a simple round of
Furthermore, we submitted patients who gave their consent        telephone conversation with HA preoperatively.



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F. Forli et al.




Table I. Characteristics of the cohort.                                 tion score with background noise, indeed, was found to be
 Patients, n                                                  49        significantly positively correlated with the pre-CI open-set
 Males, n (%)                                              25 (51%)     recognition score in silence and with background noise
 Use of hearing aids before implantation, n (%)           49 (100%)     (Pearson coefficient = 0,525; p < 0.001 and Pearson coef-
 Oral language users, n (%)                               49 (100%)     ficient = 0.387 p < 0.01 respectively). The post-CI open-set
 Age at diagnosis (years), mean (min-max)                 2,3 (0.1-8)   disyllabic recognition score in silence and with background
 Age at CI (years), mean (min-max)                       33,9 (16-60)   noise was not significantly correlated with age at first HA
 Progression of hearing loss                                            fitting (p = 0.302 and p = 0.608 respectively) or pre-CI
   Stable, n (%)                                          21 (43%)      thresholds with HA (p = 0.206 and p = 0.319, respectively)
   Progressive, n (%)                                     28 (57%)      and without HA (p = 0.813 and p = 0,958, respectively).
 Aetiology of hearing loss                                              At multivariate analysis, even if the post-CI open-set disyl-
   Genetic (Connexin 26 or 30 mutations, other), n (%)    5 (10%)       labic recognition score in silence was confirmed as signifi-
   Large vestibular aqueduct syndrome, n (%)                2 (4%)
                                                                        cantly and positively correlated with the pre-CI open-set
   Prenatal infection, n (%)                               8 (16%)
                                                                        recognition score in silence (RC = 0.632 (0.244-1.021)
                                                                        p = 0.002), the post-CI open-set recognition score with
   Unknown, n (%)                                         34 (69%)
                                                                        background noise, significantly correlated only with the
 Educational level
                                                                        pre-CI open-set recognition score with background noise
   University graduate                                     8 (16%)
                                                                        (RC = 2.723 (0.104-5.344) p = 0.042).
   High school certificate                                25 (51%)
                                                                        Prelingually deafened patients with a history of progres-
   Secondary school certificate                           16 (32%)
                                                                        sion of hearing loss showed significantly better results post-
                                                                        CI open-set speech recognition abilities, both in silence
                                                                        (p = 0.002) and with background noise (p = 0.007). This
In 34 patients, the aetiology of hearing loss was idiopathic            result was also confirmed with multivariate modelling with
(undefined). In 8 patients, hearing loss was related with               multiple linear regression (RC = 20.9 (4.9-37) p = 0.012
maternal infections during pregnancy (cytomegalovirus,                  and RC = 16.2 (4.06-28.3) p = 0.010).
rubella, toxoplasmosis, parotitis) and in 5 cases with ge-              With ANOVA for repeated measures testing, we observed
netic mutations (Connexin 26, Connexin 30, PDS, Chud-                   a significant higher improvement in post-CI speech percep-
ley-McCulloch syndrome). In 3 cases, the hearing loss was               tion in silence in patients with a university degree (p < 0.01)
associated with an enlarged vestibular aqueduct (2 non-                 (Fig. 1). Also, post-implantation speech recognition scores
syndromic enlarged vestibular aqueduct, 1 Pendred syn-                  with background noise improved more in patients with a
drome).                                                                 university degree, but the difference between the groups
Twenty-eight (57%) of patients experienced progression of               was not statistically significant (p = 0.310).
hearing loss, even if to a variable degree.
Eight patients were university graduates, 25 had a high
school certificate and 16 a secondary school certificate,
according to the UPQ questionnaire. Educational level
was not correlated with pre-operative speech perception
scores in silence or with background noise (p = 0.837 and
p = 0.505, respectively). The score at SPM ranged from 59
to 16, with a mean value of 45.84.
After cochlear implantation, the mean free-field threshold
with CI was 38.2dB (35-55dB). Postoperative open speech
recognition score with CI was 51.7% (0-100%) in silence
and 23.1% (0-80%) in noise. Postoperatively, 23 patients
(46-9%) were capable of sustaining a simple round of tel-
ephone conversation with CI, even if with variable degrees
of performance.
At univariate analysis, post-CI open-set disyllabic recogni-
tion score in silence significantly positively correlated with
                                                                        Figure 1. Pre-CI open-set recognition score in silence compared with post-
the pre-CI open-set recognition score in silence (Pearson               CI open-set recognition score in silence by ANOVA for repeated measures
coefficient = 0,477 p = 0,001). Post-CI open-set recogni-               stratified for educational level.



176
                                                                                           Cochlear implant in prelingually deafened adults




Regarding the correlation between SPM results and post-             subjective benefits in a group of 30 prelingually deafened
operative recognition results in silence and in noise, we           implanted adult patients.
found a weak positive association but no statistical signifi-       The patients in the present study gained significant benefits
cance (Pearson coefficient = 0.146; p = 0.496 and Pear-             after implantation, with a mean disyllabic word recognition
son coefficient = 0.076 p = 0.724, respectively). It must           score of 51.7% (0-100%) in silence and 23.1% (0-80%) in
be considered that SPM was administered only to 29 of 49            noise.
patients.                                                           It is well known that outcomes after CI in prelingually
                                                                    deafened adults are variable as stressed in the recent inves-
Discussion                                                          tigation by Debruyne et al. 12. In 27 patients, indeed, the
                                                                    results in terms of open-set word recognition ranged from
The aim of this study was to evaluate the role of prognos-          0% to 88%. Similarly, Duchesne et al. 3 reported a wide
tic factors affecting the outcome in a group of prelingual-         variability of speech perception outcomes with recognition
ly deafened patients submitted to CI in adulthood in our            scores after implantation ranging from 0 to 95% and Forli
Institution. We believe that this study can add knowledge           et al. 2 reported a disyllabic word recognition score ranging
regarding the variability of results seen in early-deafened         from 0 to 100%.
adult implanted patients and clarify the role of prognostic         In the present cohort, post-implantation results in terms of
factors.                                                            disyllabic word recognition score were also variable, rang-
Studies in the international literature in this field are limit-    ing from 0 to 100% in quiet and from 0 to 80% in noise.
ed, and mostly related to heterogeneous samples composed            This variability may be related to the wide heterogeneity
of patients with an exclusive oral communication modality,          of patient characteristics. Pre-operative factors that seem
patients communicating with sign language and patients us-          to make a significant contribution to post-operative hearing
ing total communication 7,10,12,17. This is a remarkable bias.      performance are age at onset of hearing loss and at first hear-
The educational programmes that stress oral communica-              ing aid fitting 2,4,13,14, speech perception performance with
tion as the preferred communication modality, indeed, can           hearing aids 4-6,8,18, residual hearing 8, communication mode
potentially reduce cortical colonisation of central speech          and type of rehabilitation 8, educational environment 8, mo-
and language processing centres by other sensorial modali-          tivation and psychological aspects 4-6,8,18. Moreover, in 2011
ties. Consequently, the use of oral communication since the         van Dijkhuizen et al. reported that speech intelligibility
first years of life should be an important candidacy crite-         was a predictor of post-implantation hearing results in a
rion in cochlear implantation of patients with long-term            group of prelingually deafened adults 13,14. More recently,
prelingual deafness, and a fundamental factor underlying            in 2017, in a study on 27 patients Debruyne et al. indicated
the potential for speech perception with a CI 4-6.                  that postoperative performance in terms of speech percep-
This is one of the few papers that deals this topic reporting       tion with CI could be explained to a large extent by two
on patients using oral communication exclusively. In this           pre-implantation factors: preoperative pure tone audiom-
regard, it is useful to underline that in Italy, since the 1960s,   etry and preoperative consonant-nucleus-consonant (CNC)
oralism has been the main rehabilitative choice for patients        word test 12. A recent paper by Ghiselli et al. showed that
suffering from preverbal deafness. As a result, in Italy, most      an early and prolonged auditory stimulation in prelingually
adult patients with preverbal hearing impairment seeking a          deafened cochlear implant recipients may have an impor-
CI received hearing aids at early ages and developed oral           tant role in determining good post-CI results 19.
language, even if at variable degrees of performance.               In our sample, some factors indicating good and early
The results reported in the literature in early hearing-im-         acoustic stimulation were correlated with better post-op-
paired adult patients implanted in adulthood are usually sat-       erative speech perception results. In this regard, we found
isfactory in terms of speech perception and of subjectively         that the pre-operative speech perception with HA and
perceived benefits, including an improvement in quality of          progression of hearing loss before implantation were cor-
life. In fact, Duchesne et al. 3 recently reported the post im-     related with good post-implantation results. Both factors
plantation results of 21 prelingually deafened patients; half       indicate some extent of auditory input in the first periods of
of participants showed significant improvement in speech            life. Nevertheless, we could not demonstrate a correlation
recognition performance compared with the pre-implant               between speech perception results and age at first hearing
condition. Moreover, a few participants attained speech             aid fitting or pure tone audiometry with HA and without
recognition levels typically found in adults with postlin-          HA before implantation. This finding could be due to the
gual deafness. In the same year, Forli et al. 2 reported a          small size of the sample and to the heterogeneity of vari-
significant improvement in terms of speech perception and           ables among patients for aspects universally considered to



                                                                                                                                     177
F. Forli et al.




play an important role in conditioning post-implantation          Conclusions
results, such as degree of hearing loss in the first years of
                                                                  In conclusion, our study offers a further confirmation that
life, or early stimulation with HA. The small and heteroge-
                                                                  prelingually hearing impaired adult patients may achieve
neous sample of patients make it difficult to understand the
                                                                  significant benefits in speech perception after implanta-
exact role of each factor in conditioning the results.
                                                                  tion, even if with a high degree of variability. Among the
We also correlated educational level with post-implant
                                                                  prognostic factors, indicators of good and early acoustic
speech perception. We found significantly higher improve-
                                                                  stimulation are correlated with better post-operative speech
ment of open-set speech recognition score in silence after
                                                                  perception results. In this regard, we found a significant
implantation in subjects with a higher level of education.        correlation between pre-operative speech perception scores
Few other papers have analysed the impact of educational          with hearing aids and post-operative results and between
level on post-CI results in terms of speech perception in         the progression of hearing loss and post-operative results.
prelingually severe-to-profound hearing impaired delayed          An effective auditory input in early life may have led the
implant patients without finding any significant correla-         patients’ auditory cortex to develop properly, allowing
tions 8,20.                                                       them to gain satisfactory results of speech perception after
We also investigated cognitive function as a possible prog-       implantation.
nostic factor in late implanted prelingually hearing impaired     In this special group of patients, cognitive aspects may play
patients, as is broadly reported in literature that executive     a role in achieving good post-operative speech perception
functioning and especially working memory are correlated          skills, but our data do not have statistical significance and
with speech recognition outcomes in CI users 21-25.               further studies and more data on this topic would be useful.
We hypothesised that better cognitive abilities could help
patients to better discriminate sounds and language and, in
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                                                                  6
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