Auditory and speech outcomes of cochlear implantation in patients with Waardenburg syndrome: a meta-analysis

Objective This study aims to assess the potential efficacy of cochlear implantation as a treatment for patients with Waardenburg syndrome (WS) and to guide clinical work by comparing the effect of auditory and speech recovery after cochlear implantation in patients with WS and non-WS. Methods PubMed, the Cochrane Library, CNKI, and Wanfang Data were sources for retrieving literature on cochlear implantation in WS, and clinical data meeting the inclusion criteria were meta-analyzed using RevMan5.41. Results A total of nine articles were included in this study, including 132 patients with WS and 815 patients in the control group. Meta-analysis showed that there are no significant differences in the scores for categories of audit performance (CAP), speech intelligibility rating (SIR), and parents’ evaluation of aural/oral performance of children (PEACH) between the WS group and the control group. Conclusion Cochlear implantation demonstrates comparable auditory and speech recovery outcomes for WS patients and non-WS patients.


Introduction
Waardenburg syndrome (WS), discovered and named by Dutch physician Waardenburg in 1951 (1), is an autosomal dominant genetic disorder primarily characterized by auditory pigmentary abnormalities.Its key manifestations include inner canthus heterotopia, iris heterochrony, white hair on the forehead, and hereditary sensorineural deafness (2).WS is closely related to the abnormal migration and differentiation of melanocytes.In the inner ear, melanocytes differentiate into intermediate cells within the stria vascularis of the cochlea (3,4).When gene mutations affect melanocyte differentiation and migration, they may influence the cochlea's internal environment, resulting in sensorineural hearing loss.
Cochlear implantation (CI) stands out as the primary approach for auditory and speech therapy (5).Currently, there exists a scarcity of research samples and variations in evaluation criteria for assessing the effectiveness of CI in WS patients.Therefore, this paper aims to conduct a comprehensive literature review, identify common evaluation indicators, and evaluate the therapeutic impact of CI on patients with WS.

Literature heterogeneity test
Heterogeneity tests were conducted for each test, and fixed-effects model analysis was performed on categories of audit performance (CAP), speech intelligibility rating (SIR), and parents' evaluation of aural/oral performance of children (PEACH) scores (p > 0.05, I 2 < 50%).

Comparison of postoperative CAP scores
Six studies, involving a total of 722 cases (72 cases in the WS group and 650 cases in the control group), compared the CAP scores of the WS group and the control group after CI.The fixed-effect model was used for analysis, and the combined-effect test result yielded Z = 1.44, p = 0.15.This suggests that there is no statistical difference between the WS group and the control group in terms of CAP scores, as shown in Figure 2.

Comparison of postoperative SIR scores
Six studies, involving a total of 722 cases (72 cases in the WS group and 650 cases in the control group), compared the SIR scores of the WS group and the control group after CI.The fixed-effect model was used for analysis, and the combined-effect test result yielded Z = 1.05, p = 0.29.This indicates that there is no statistical difference between the WS group and the control group in terms of SIR scores, as shown in Figure 3.

Comparison of telephone scores
Two studies, involving a total of 90 cases (37 cases in the WS group and 53 cases in the control group), compared the telephone scores of the WS group and the control group after CI.The fixedeffect model was used for analysis, and the combined-effect scale test result yielded Z = 0.42, p = 0.68.This reveals that there is no statistical difference between the WS group and the control group in terms of the comparison of telephone scores, as shown in Figure 4.

Comparison of quiet environment scores
Two studies, involving a total of 90 cases (37 cases in the WS group and 53 cases in the control group), compared the quiet   Process of literature screening.Forest map of telephone communication score comparison between the WS group and the control group.Forest map of quiet score comparison between the WS group and the control group.
environment scores of the WS group and the control group after CI.The fixed-effect model was used for analysis, and the combinedeffect scale test result yielded Z = 0.12, p = 0.91.This indicates that there is no statistical difference between the WS group and the control group in terms of quiet environment scores, as shown in Figure 5. Forest map of CAP comparison between the WS group and the control group.
Forest map of SIR comparison between the WS group and the control group.

Comparison of noise environment scores
Two studies, involving a total of 90 cases (37 cases in the WS group and 53 cases in the control group), compared the noise environment scores of the WS group and the control group after CI.The fixed-effect model was used for analysis, and the combined-effect test result yielded Z = 0.15, p = 0.88.This suggests that there is no statistical difference between the WS group and the control group in terms of noise environment scores, as shown in Figure 6.

Publication bias analysis
The literature exhibits inconsistency in the included evaluation indicators.A funnel plot was generated for bias analysis of each study, and the results showed that the literature was symmetrically distributed on both sides, indicating an absence of publication bias.However, during SIR analysis, one literature source exhibited high heterogeneity.

Discussion
Waardenburg syndrome can be categorized into four types based on its clinical manifestations.Type 1 presents with ectopic inner canthus, sensorineural deafness, heterochromatic iris, white frontal hair, hypopigmentation, and straight eyebrows.Type 2 lacks ectopic inner canthus but is otherwise similar to Type 1. Type 3, also known as Klein Waardenburg syndrome, is characterized by the features of Type 1 along with muscular dysplasia and upper limb contracture, Type 4, identified as Waardenburg Shah syndrome or Waardenburg Hirschsprung disease, corresponds to Type 2 and is accompanied by Hirschsprung disease.Types 1 and 2 collectively constitute a significant proportion (16,17).About 60% of individuals with WS types I and III suffer from sensorineural hearing loss, while 90% of those with types II and IV experience sensorineural hearing loss (18).Some genes are believed to be related to the onset of WS.According to current research, PAX3 is related to the pathogenesis of WS1 and WS3 (19,20), MITF and SNAI2 play a role in the pathogenesis of WS2 (21), SOX10 is related to the pathogenesis of WS2 and WS4 (22,23), EDNRB and EDN3 are related to the pathogenesis of WS4 (24,25).Some WS patients are accompanied by semicircular canal dysplasia, cochlear dysplasia, and large vestibular aqueduct.Structural malformations of the cochlear and labyrinth have not been reported (17).At present, most studies show that patients with WS recover well after CI, but some studies still report that the postoperative effect on patients is not good (7).Lovett et al. ( 2) compared the hearing and speech outcomes of WS patients before and after CI.The results showed that CI can be an effective way for improving the hearing and speech ability of WS patients.But we still want to find out whether WS and non-WS have a similar prognosis.
Both CAP and SIR were proposed by Nikolopoulos et al. of Nottingham University and filled in by patients' relatives (26,27).These assessments provide straightforward information about children's hearing levels and speech abilities following surgery, making them widely used for evaluating the postoperative rehabilitation outcomes of cochlear implants (7,8).In this study, six sets of investigations utilized CAP and SIR scores to assess auditory and speech abilities in the two groups.The results indicated no significant difference in postoperative CAP and SIR scores between the WS group and the control group.
Parents' evaluation of aural/oral performance of children was developed by the National Acoustic Laboratory (NAL) (28) and is used for the evaluation of the auditory speech effect after cochlear implantation.Trained professionals administer the evaluation by prompting parents with questions, and responses involve describing specific cases, offering evidence of auditory speech recovery.This approach helps avoid the potential bias of direct "yes" or "no" responses, contributing to a more objective assessment (29).In this analysis, two studies utilized the PEACH score, and the results indicated no significant differences in postoperative telephone scores, quiet environment scores, and noise environment scores.

Limitations
This study has some limitations.First, the analysis is constrained by the inclusion of only a small number of studies.Second, the absence of detailed information regarding WS types and underlying genotypes hinders further discussion and exploration.Third, some of the included research samples have small populations, potentially impacting the generalizability of the findings.Fourth, in some studies, the operation time of patients was not consistently reported, introducing variability in the data.Finally, the majority of studies are from China, suggesting a geographical bias.The study calls for more diverse Forest map of noise score comparison between the WS group and the control group.data from other countries to enhance the breadth and applicability of the findings.

Conclusion
There was no obvious difference in the auditory and speech recovery effects between WS patients after cochlear implantation and individuals undergoing other cochlear implant procedures.Cochlear implantation emerges as an effective method for auditory and speech therapy in WS patients, demonstrating favorable postoperative recovery effects.However, substantiating this conclusion requires a large number of highquality disease control studies to provide robust evidence and validation.
NOS, Newcastle Ottawa Scale; CAP, Categories of audit performance; SIR, Speech intelligibility rating; MAIS, Meaningful auditory integration scales; MUSS, Meaningful use of speech scale; CSW-OSW, Closed-set and open-set words; PTA, The pure tone audiometry; PEACH, Parents' evaluation of aural/oral performance of children; RDLS, The Reynell Develop-mental Language Scales; LQ, Language quotient.

TABLE 1
The basic features of the included study.