DE LOS FUNCIONARIOS Y EMPLEADOS Concepto

Our first objective in the present study was to investigate whether cochlear implantation resulted in improvement in subjective benefit in prelingually deafened adults. Unlike other studies, we evaluated a larger group of patients. Both the disease-specific and generic questionnaires showed significant im- provements in quality of life after implantation. It should be noted that as the study group only included prelingually deafened adults who had some auditory input in the past and who used primarily aural-oral communication. Prelingually deafened without auditory input in the past or using sign language were not implanted, as previous studies showed that they have poor benefit of CI (Teoh et al., 2004b). So our results can not be generalized to all prelingually deafened adults. It should also be noted that 7 of the 35 patients did not return any questionnaire. In case these 7 patients did return their questionnaires, we expected that our results will not have been influenced in a negative way, as their medical records indicate that these patients continue to use their implant. In addition to this, according to the medical files, all included 28 patients continue to use their implant on daily basis.

  100 80 60 40 20 0

speech perception benefit phoneme scores (%)

100 80 60 40 20 0 ben ef it sc ore of N C IQ phy si ca l 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 9 8 4 3 2

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Nevertheless, the results of this study showed an important benefit in quality of life this specific group, largely similar to those results found by Klop et al. and van Dijkhuizen et al. (Klop et al., 2007; van Dijkhuizen et al., 2011). Klop et al. and van Dijkhuizen et al. found fewer significant improvements (i.e. in fewer domains), what might be due to the smaller number of patients included in their studies (n=8 respectively 9).

With regard to speech production, scores for the NCIQ subdomain “speech production” in the present study significantly improved. Improved auditory feedback after implantation might have contributed to the improved quality of speech production. That the HUI-3 subdomain “speech” did not improve might be explained by the fact that this domain assesses the intelligibility for the listener of other people’s speech. In addition to intelligibility, the NCIQ subdomain “speech production” contains questions on voice control and loudness control. The positive influence of these factors probably resulted in the significant improvement in speech production as assessed with the NCIQ, but not in the speech intelligibility as measures using the HUI-3.

Although there was no improvement in the domain “speech” of the HUI-3, the mean HUI utility score increased as a result of improvement in the “hearing” and “emotion” domains. Klop et al. used an earlier version of the HUI, namely the HUI-2. Unlike the HUI-2, the HUI-3 includes the domains “vision”, “hearing” and “speech”. Similar to our study, Klop et al. also found a significant change in mean HUI utility score but, probably due to small group size, they did not find significant improvements in the attribute “emotion” (Klop et al., 2007).

The third instrument used in this study was the GBI. Our results showed a significant improvement in overall score and in the general and social support subscales. Although no improvement was found in the physical health subscale, this was not surprisingly because this subscale contains questions about being sick, using medicine or visiting a doctor. This subscale score can be interpreted as a dummy variable (i.e. significant improvement of this item would indicate that the questionnaire was influenced by enthusiasm bias, which was not found).

In addition to this it must be taken into account that, even when dummy variables did not significantly improve, enthusiasm or psychological factors may still lead to an improved perceived quality of life. The pre-implant counselling might influence such factors. In the present study all patients were informed about the possible limited benefit of implantation (see Materials and Methods section). Especially in this group, it remain of high importance that adequate and appropriate pre-implant counselling is given.

The improvement in quality of life of the prelingually deafened group is in line with earlier studies evaluating quality of life in postlingually deafened adults. Postlingually deafened adults improved in all subdomains of the NCIQ and in the HUI subdomains “hearing” and “emotion” too (Damen et al.,

2007). However, the absolute differences between preoperative and postoperative scores were larger in the postlingually deafened group due to the lower preoperative scores of the postlinguals compared to the prelinguals. This indicates that, compared to postlingually deafened subjects, prelingually deafened subjects experienced their preoperative hearing limitations as being less severe. In agreement with this, the overall GBI scores in postlingually deafened patients were higher, when we compared the prelingual data to that of postlinguals, as reported by Vermeire et al. (Vermeire et al., 2005). Larger improvements in NCIQ and HUI scores and higher GBI scores in the postlingually deafened patients can also be caused by larger improvements in hearing and speech recognition abilities after implantation. With regard to the relationship between subjective benefit and speech recognition, we also investigated whether the reported changes in quality of life are related to changes in the patients’ ability to recognize speech. Although previous literature suggested that the amount of subjective benefit is unrelated to the amount of improvement in speech recognition after implantation in late-implanted prelingually deafened adults, no correlation analyses were reported (Zwolan et al., 1996). Our study showed no significant correlations between quality of life measures and speech recognition benefit scores (i.e. postoperative minus preoperative phoneme score) and no correlation between the NCIQ physical domain (which assesses sound perception and speech perception) and the speech recognition scores. This was partly a result of one subject (patient 23) who showed low postoperative speech recognition scores (phoneme score < 10%) yet showed large improvements in the physical domain as a result of improved basic sound perception. Although this individual had low speech recognition scores, the patient experienced improved quality in life as a result of improved perception of sounds. The absence of correlation between subjective benefit and speech recognition in prelingually deafened patients indicates that quality of life is not only influenced by speech recognition abilities. This seems to be in contrast to postlingually deafened patients (Francis et al., 2002; Vermeire et al., 2005). An explanation for this difference between postlingually and prelingually deafened adults might be that the impact of regaining speech recognition is important in postlinguals for their daily functioning and communication. In contrast, prelingually deafened adults might be satisfied with only hearing sounds. In this prelingually deafened group minimal hearing abilities, like hearing environmental sounds and the availability of additional auditory cues in daily communication, results in large improvements in quality of life. We recommend future studies include quality of life measures in addition to speech recognition scores to evaluate post-implant performance.