**4. Discussion**

The present study showed that cochlear reimplantation in children was efficient and associated with a predictable overall increase in audiological performances. Adherence to the speech rehabilitation program was associated with better audiological outcomes.

According to our results, word discrimination scores improved or were stable in 84% of patients; the scores showed poorer performance (i.e., decrease of more than 10%) in only 16% of patients. These results are in line with other reports in the literature: deterioration of audiological performances in only 2.9% for Rivas et al. [16], 37% for Henson et al. [17], and 10% for van der Marel et al. and Orús Dotú [18,19]. We did not observe any statistical correlation of these poorer results with sex, age, etiology of deafness, indication, time since the first implantation, and angle of reinsertion of the electrode array, consistent with other studies [20–24]. However, the audiological performance before reimplantation was found to be associated with the audiological outcomes: the patients with low scores tended to have a significant gain (up to +300%), whereas patients with high scores maintained these good performances after reimplantation (variation of less or more than 10%). This is an encouraging result, as patients with CI offering good performances seemed not to be at risk of significant decrement after reimplantation. This outcome favors the feasibility of replacing the old CI for technological upgrading without risking audiological performance decrement [12]. However, we observed that patients with suboptimal speech rehabilitation presented a median decrease of −19% in their performances. This finding is new in the context of cochlear reimplantation. It is in line with similar reported results after cochlear implantation [3]. In our center, the therapy consisted of teaching the child to use their residual hearing with optimal amplification (listening therapy) allowing the additional use of speechreading and/or natural gestures. The goal of these visual cues was to aid the child to understand the spoken language. The program also aimed to foster parental involvement, and to teach them how to create an optimal listening learning and language

environment in everyday life, child's daily routines, and play activities. Based on our findings, it seems that cochlear reimplantation should be associated with a thorough speech rehabilitation program to offer the best audiological outcomes after the intervention. Because of the retrospective design of our study, and the length of the cohort, it was difficult to quantify the speech rehabilitation program and analyze potential associated factors. We thus defined suboptimal rehabilitation as participation of less than 50% of the program. Non-adherence to the program (12% of the cohort) was because of the patient's unwillingness, other intercurrent conditions (severe epilepsy, depression), or because of severe tinnitus in one case. It can be discussed that these factors by themselves could interfere with the audiological performances, and further studies need to be designed to understand the specific role of each factor. Moreover, the number of patients was small, and the calculation of a relative risk was not meaningful in this context because the confidence interval was too wide.

In our cohort, cochlear reimplantation presented a high success rate (94%). Only few studies are available in the literature on the pediatric population. One recent study observed a similar rate of 85% [6]. As in our cohort, the failure of cochlear reimplantation has revealed a central origin in some patients. They suspected an evolutive auditory neuropathy spectrum disorder in one case, and cochlear nerve hypoplasia in another case. In young children, the diagnosis of soft failure is often challenging. The absence of language development after implantation or the audiological performance decrement can evoke a soft failure [9]. However, other diagnoses can have the same presentation. In this context, the absence of language development may correspond to auditory neuropathy spectrum disorder, whereas audiological performance decrement may correspond to a degenerative central pathology. Finally, neurological delay or psychiatric conversion disorder are other possible final diagnoses if the reimplantation fails to restore the audiological performance [22]. Hence, several studies agree to consider that in these situations, as electrophysiological tests fail to reliably determine internal component functional status, the only option is to propose explantation–reimplantation [6,9,10].

In our study, another possible reason for failure in one case was the insertion of the electrode array in the scala vestibuli because of an ossified scala tympani. This patient's score decrease by 26%. Audiological results after insertion into the scala vestibuli are reported to be worse, with an average score of word discrimination of 50% [25,26]. The insertion in the scala vestibuli could offer greater results if the scala media is not injured [27]. However, this technique presents a high risk of secondary degeneration of spiral ganglion neurons and remains a last chance option.

This study has several limitations. The retrospective design did not allow the analysis of certain data such as the quantification of the speech rehabilitation program. Moreover, it resulted in 47% of missing data, for the value of angle of insertion based on computed tomography. However, for our primary outcome, the audiological scores during 3 years after reimplantation were available for 75% of the cohort. Because of the indications of cochlear reimplantation, the cohort was also heterogeneous and of a relatively small size. However, its size remains average compared with the previously reported cohort [6,9,23]. Our long experience in cochlear implantation and the single-center design ensured that no major modification of the decision algorithm occurred during the study period. However, it may have introduced selection bias and may limit the possibility of generalizing these results.

#### **5. Conclusions**

Audiological performance improved after cochlear reimplantation in children. This intervention was highly efficient and tended to ensure stable performance in the patients with previously good audiological scores. Speech rehabilitation was an important factor associated with favorable audiological outcomes.

**Supplementary Materials:** The following supporting information can be downloaded at: https:// www.mdpi.com/article/10.3390/jcm11113148/s1, Figure S1: Time after initial implantation (years).

**Author Contributions:** Conceptualization, M.M. and F.B.; methodology, M.M. and F.B.; formal analysis, F.B.; investigation, F.B., C.B., M.S. and F.M.; data curation, F.B., C.B., M.S. and F.M.; writing original draft preparation, F.B.; writing—review and editing, M.M., C.B., F.V. and F.B.; supervision, M.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** The study was conducted in accordance with the Declaration of Helsinki.

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** The authors thanks Adrien Caplot for the review of the statistical analysis.

**Conflicts of Interest:** The authors declare no conflict of interest.

## **References**

