Cochlear implantation in patients with enlarged vestibular aqueduct. A case series with literature review

Cochlear implantation in adults and pediatrics with enlarged vestibular aqueduct: a systematic review on the surgical findings and patients' performance

PURPOSE

Cochlear implantation (CI) has been considered a safe and effective management option for patients with severe to profound hearing loss. Patients with enlarged vestibular aqueduct (EVA) could be challenging with some variations in surgical approaches, intraoperative surgical notes, and clinical outcomes. This study aimed to  review the surgical and clinical outcomes of cochlear implantation among patients with EVA.

MATERIALS AND METHODS

A systematic literature search was carried out in five major databases. All original studies reporting cochlear implantation in patients with EVA were included for qualitative data synthesis. The risk of bias was independently assessed through the National Intuitional of Health tool. The review protocol was registered in PROSPERO (reference number: CRD42021225900).

RESULTS

A total of 34 studies with 4035 subjects were included. Of them, 853 (21.14%) had EVA and underwent CI. Mondini malformation was the most frequently associated anomaly (n = 78, 11.1%). Unilateral implantation was performed in 258 cases while bilateral in 119 subjects. Postoperative complications included CSF/perilymph gusher (n = 112), CSF oozing (n = 18), and partial electrode insertion (n = 6). Closing the cochleostomy with temporalis fascia, muscle, connective tissue, or fibrin glue was the most frequently reported approach to manage CSF/perilymph gusher (n = 67, 56.7%) while packing was performed in six patients.

CONCLUSION

Patients with EVA demonstrated audiometric and speech performance improvement after CI. However, many patients had intra- or postoperative complications. Further research is needed as the outcomes may be affected by associated temporal bone pathology, the timing of implant, and hearing condition.

Outcomes of Acoustic and Linguistic Performances Following Cochlear Implantation in Large Vestibular Aqueduct Syndrome (LVAS)

AIM

This study aims to collate the outcomes in acoustic and linguistic performances after cochlear implantation in LVAS.

METHODS

In a hospital-based prospective interventional study, seven prelingual children with bilateral profound sensorineural hearing loss (SNHL) with LVAS were recruited. They underwent unilateral cochlear implantation between December 2013 and December 2015 in the Department of Otorhinolaryngology and Head Neck Surgery at a tertiary care center. Outcomes of auditory and speech performances were assessed in the form of revised categories of auditory perception (CAP), infant toddler meaningful auditory integration scale (IT-MAIS) and speech intelligibility rating (SIR) scores preoperatively, at one and two years follow up.

RESULTS

The mean age of implantation was 4 years. The median revised CAP, IT-MAIS, and SIR scores after one and two years of follow-up were 6, 27, 3, and 11, 36, 5 respectively. The mean follow-up duration was 21.3 months.

CONCLUSION

Pre op median revised CAP, IT-MAIS, and SIR scores of 0, 1, 1 showed improvement to 11, 36, 5 at two years follow up which was statistically significant. Hence, we conclude that good functional outcomes post-operatively advocate the significance of cochlear implantation in LVAS.

Cochlear Implantation in Children with Enlarged Vestibular Aqueduct: A Systematic Review of Surgical Implications and Outcomes

OBJECTIVES

This study investigated age at implantation, improvement in hearing and speech perception outcomes, as well as surgical complications in pediatric cochlear implant recipients with Pendred Syndrome (PS) or non-syndromic enlarged vestibular aqueduct (NSEVA).

DESIGN

A systematic review of the literature between 1984 and 2021 was performed. Two independent reviewers performed abstract and full-text screening using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. The inclusion criteria were: English language, cochlear implant, age at implantation available, age <18 years, PS, Mondini malformation, and enlarged vestibular aqueduct. Full-text analysis was completed using the National Institute of Health assessment tool for case series and case-control studies. Studies were also graded according to the Oxford Centre for Evidence-Based Medicine grading system.

RESULTS

In total, 198 studies were identified and screened, and 55 studies were included for analysis. Audiological outcomes were available in 46 studies, and the four-frequency pure-tone audiogram average improved by 60 to 78 dB HL due to cochlear implantation. Auditory performance and speech intelligibility scores increased by 44%. The overall average implantation age was 60 months. The implantation age was 21 months lower in the studies where individuals were implanted after the year 2000 compared with those implanted before the year 2000. Perilymph gusher/oozing was the most common surgical incident reported, occurring in 187 of 1572 implantations.

CONCLUSIONS

In children with PS/NSEVA, cochlear implantation improves pure-tone average by 60 to 78 dB HL and capacity of auditory performance/speech intelligibility by 44%. The implantation age for these children has decreased during the last two decades but is still somewhat higher than reported for unselected pediatric cochlear implantation. Perilymph gusher/oozing is the most common surgical complication.

Cochlear Implantation in Pediatric Patients With Enlarged Vestibular Aqueduct: A Systematic Review

OBJECTIVE(S)

To describe cochlear implantation (CI) outcomes, with speech perception, auditory, language, and parent-reported auditory and speech behaviors, in children with an enlarged vestibular aqueduct (EVA) and incomplete partition type 2 (IP-II) and compare to control children without inner ear malformations (IEMs) and to determine cerebrospinal fluid gusher rates and effect on outcomes.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

MEDLINE, Embase, Cochrane, and CINAHL databases were searched from inception to February 2020. Studies reporting relevant outcomes in children with EVA or EVA + IP-II and controls without IEMs undergoing CI were included. Mean differences in speech perception, auditory, and language scores between cases and controls were meta-analyzed. Gusher rates were determined by proportion meta-analyses.

RESULTS

Of 214 identified articles, 42 met inclusion criteria, evaluating 775 cases and 2,191 controls. Of -cases, 578 (74.6%) had EVA and 197 (25.4%) had EVA + IP-II. Cases showed a significant improvement in speech perception, auditory and language performance, comparable to controls. Parent-reported auditory and speech production behaviors outcomes were positive among cases and comparable to controls. Pooled gusher proportions in EVA and EVA + IP-II cases were 27.7% (95% CI: 17.6-39.1) and 48.6% (95% CI: 28.6-69.0), respectively, with a proportion difference of 20.9% (95% CI: 11.0-30.1). Gusher occurrence did not impact speech perception or language outcomes.

CONCLUSION

Outcomes in children with EVA or EVA + IP-II undergoing CI are favorable and largely comparable to outcomes in children with hearing loss undergoing CI without IEMs. Intraoperative gusher is more prevalent among children with EVA + IP-II as compared to iEVA. Gusher does not influence speech perception and language development outcomes.

LEVEL OF EVIDENCE

NA Laryngoscope, 2021.

Enlarged Vestibular Aqueduct: Hearing Progression and Cochlear Implant Candidacy in Pediatric Patients

HYPOTHESIS/OBJECTIVE

Investigate the rate of hearing loss progression and incidence of cochlear implant candidacy in children with enlarged vestibular aqueduct (EVA).

BACKGROUND

EVA is the most common congenital malformation of the inner ear, is responsible for a large percentage of children with hearing loss, and is associated with hearing loss progression. Rates and degree of progression of hearing loss to cochlear implantation candidacy have not been well described.

METHODS

Review of children with EVA who presented to a single academic medical center. Audiometric data were reviewed to determine subjects who met criteria for cochlear implantation (≥75 dB pure-tone average) at presentation. For those not meeting criteria, serial audiometric data were reviewed for progression to candidacy.

RESULTS

A total of 257 ears met inclusion criteria. One hundred ninety-two (74.7%) met cochlear implant candidacy criteria by age 12, yet only 117 ears (60.9%) actually received implants before turning 13. One hundred fifty-three ears (59.5%) met implant candidacy criteria at presentation. Nearly 50% of those not initially meeting implantation criteria had a ≥15 dB shift in pure-tone average by age 12, with 37.5% of this subgroup meeting implant candidacy criteria before their teen years at an average age of 7.10 years.

CONCLUSION

The majority of children with EVA reach cochlear implant candidacy before reaching adulthood, yet implantation rates for candidate ears remain at 60% and delay in implantation persist. Parents of children with EVA should be counseled on the likelihood of progression and closely monitored for cochlear implant candidacy.

Audiologic Outcomes of Cochlear Implantation in Cochlear Malformations: A Comparative Analysis of Lateral Wall and Perimodiolar Electrode Arrays

OBJECTIVE

Cochlear implantation in children with inner ear malformations has been shown to be beneficial. The aims of this study are to evaluate open set word recognition outcomes among children with cochlear implants who have cochlear malformations, and to further assess if either the lateral wall (LW) or perimodiolar (PM) electrode arrays confer any performance outcome advantages.

STUDY DESIGN

Retrospective case series.

SETTING

Tertiary referral center.

PATIENTS

Pediatric cochlear implant recipients with cochlear malformations who were implanted at our institution within the last 10 years and had speech perception scores were eligible for inclusion in the study. Potential participants were excluded if they had less than 1 year of listening experience with the cochlear implant or suspected cochlear nerve deficiency.

INTERVENTION

None.

MAIN OUTCOME MEASURE

Most recent consonant-nucleus-consonant word score.

RESULTS

ANOVA analysis demonstrated that the type of cochlear malformation was significantly associated with speech perception outcome (p = 0.006). Those with IP2 malformations had significantly better word recognition outcomes than the remaining cochlear malformations. Array type (LW or PM) was not associated with better word recognition outcomes in long-term follow-up of patients with IP2 malformations (p = 0.13).

CONCLUSIONS

In children who have cochlear malformations, cochlear implantation results in varying word recognition outcomes based on the type of malformation. While the participants in this study demonstrated postoperative open set word recognition skills, those with IP2 malformations demonstrated the most benefit. Electrode type was not found to significantly impact outcomes in this cohort.

Vestibular impairment in cochlear implanted children presenting enlarged vestibular aqueduct and enlarged endolymphatic sac

Enlarged vestibular aqueduct (EVA) is a common finding in tomodensitometry. When cranial MRI is performed, enlarged endolymphatic sac (EES) can also be found. Profound hearing loss is a common finding in these patients but a few studies have investigated vestibular function after cochlear implantation (CI) in EVA and EES patients. Our main objective was to find out whether in EVA children candidates to CI, a higher endolymphatic sac (ES) volume was predictive for higher rates of postsurgical vestibular complications.

METHODS

We retrospectively included EVA children who benefited from CI, during the last 2 years. Two groups were constituted according to the presence or not of a vestibular impairment (decrease in the VOR gain on the VHIT test on one of the semicircular canals and/or a loss of cVEMPs) 6 months after CI. Endolymphatic volume of both VA and ES was measured for each patient.

RESULTS

Fifteen patients were included. The mean endolymph volume was significantly higher in the impaired group (0.40 cm³ ± 0.23, range 0.08-0.70) than in the non-impaired group (0.11 cm³ ± 0.07, range 0.04-0.29; p = 0.029). Four children of the impaired group were followed during one year. At the end of vestibular rehabilitation, all children recovered a lateral canal function and a saccular function.

CONCLUSION

In EVA children, a combined EES appears to increase the risk of severe post CI vestibular impairment. To minimize this risk prior CI surgery, besides tomodensitometry, MRI measurement of the ES volume should be systematically performed.

The biomechanical characteristics of human vestibular aqueduct: a numerical-based model construction and simulation

Vestibular aqueduct is a precise structure embedded in the temporal bone and plays a key role in the physiological function of inner ear by maintaining the endolymphatic circulation and buffering the impact from intracranial pressure. Although the alterations on the morphology or volume of vestibular aqueduct result in variety of diseases, the approaches of evaluating the condition of vestibular aqueduct are still unsatisfing because the pathological sections utilized for the 3D construction model most likely undergoes morphological changes. In this study, the vestibular aqueduct images obtained by CT scanning were processed by finite element method to construct the 3D model. To assess if this numerical model reflects the actual biomechanical properties of vestibular aqueduct, the fluid-solid coupling calculation was applied to simulate the endolymphatic flow in the vestibular aqueduct. By measuring the dynamics of endolymphatic flow, and the pressure and displacement on round membrane under external pressure, we found the numerical 3D model recapitulated the biomechanical characteristics of the real vestibular aqueduct. In summary, our approach of 3D model construction for vestibular aqueduct will provide a powerful method for the research of vestibular aqueduct-related diseases.

A novel genotyping technique for discriminating LVAS-associated high-frequency variants in SLC26A4 gene

An increasing number of biological and epidemiological evidence suggests that c.919-2A > G and c.2168A > G variants of solute carrier family 26, member 4 (SLC26A4) gene play a critical role in the development of large vestibular aqueduct syndrome (LVAS). In this study, we developed a rapid genotyping method for discriminating LVAS-associated high-frequency variants in SLC26A4 gene. The genotyping technique consists of 3' terminal exonuclease-resistant phosphorothioate-modified allele specific primer extension mediated by exo⁺ polymerase. In PCR amplification by Pfu polymerase, allelic specific primers perfectly matching wild type allele were extended while no specific products were yielded from primers targeting variant allele. Similarly, allelic specific primers perfectly matching variant allele were extended and no specific products were observed from primers targeting wild type allele. The clinical application of 3' terminal phosphorothioate-modified allele specific primer extension mediated by Pfu polymerase identified both homozygous for SLC26A4 gene c.919-2A > G variant in two patients clinically diagnosed as LVAS by temporal bone CT scan. The genetic results from this method are consistent with that of DNA sequencing. The data suggest that exo⁺ polymerase-mediated 3' terminal phosphorothioate-modified primer extension is reliable in the identification of SLC26A4 gene high-frequency variant prior to high-resolution CT scan. The method is extremely suitable for quickly molecular etiologic screening and early diagnosis and aggressive prevention therapy of LVAS.

Pre- and post-operative imaging of cochlear implants: a pictorial review

Cochlear implants are increasingly used to treat sensorineural hearing disorders in both children and adults. Pre-operative computed tomography and magnetic resonance imaging play a pivotal role in patient selection, to rule out findings that preclude surgery or identify conditions which may have an impact on the surgical procedure. The post-operative position of the electrode array within the cochlea can be reliably identified using cone-beam computed tomography. Recognition of scalar dislocation, cochlear dislocation, electrode fold, and malposition of the electrode array may have important consequences for the patient such as revision surgery or adapted fitting.

Progression of hearing loss and cochlear implantation in large vestibular aqueduct syndrome

OBJECTIVES

Large vestibular aqueduct syndrome (LVAS) is a congenital inner ear malformation that commonly results in progressive sensorineural hearing loss (SNHL) and cochlear implantation (CI). Though LVAS accounts for approximately 15% of pediatric SNHL, little is known regarding the rate and severity of SNHL in these patients. We sought to characterize the timing of SNHL progression to CI in patients with LVAS.

METHODS

We performed a retrospective chart review at our institution from 2000 to 2018 using ICD-10 "large vestibular aqueduct syndrome," and through identifying patients with CI who had LVAS. Demographic, surgical, and audiometric data were collected. Theoretical CI candidacy was approximated using a pure tone average (PTA) HL threshold of 70 dB.

RESULTS

Of 103 patients, 96 had bilateral LVAS, and 7 had unilateral LVAS. Forty-one patients had bilateral implants, 52 had unilateral implants, and 10 were not implanted. The mean age at first implant was 8.62 years old [95%CI = 6.75,10.49], the mean age at second implant was 12.24 years old [95%CI = 8.33,16.15], and the mean time between implants was 4.37 years [95%CI = 3.02,5.73]. LVAS patients reached HL threshold of 70 dB at a mean age of 5.16 years old (SD = 3.04) for the "worse ear" and 9.08 years old (SD = 4.96) for the "better ear."

CONCLUSIONS

LVAS patients are a heterogenous population of patients, in which some may undergo progression of HL and some may not. Further, there may be a discrepancy in the timing between patients' theoretical CI candidacy and when they undergo CI. In order to optimize timing of CI, individual monitoring and close observation of LVAS patients is recommended.

Bimodal strategy for excellent audiological rehabilitation in a subject with a novel nonsense mutation of the SLC26A4 gene: A case report

Sensorineural hearing loss is a heterogeneous disease caused by mutations in many genes. However, in the presence of enlarged vestibular aqueduct, it is frequently associated with mutations in the solute carrier family 26 member 4 (SLC26A4), a gene causative of a syndromic form (Pendred) as well as a non-syndromic form of hearing loss (DFNB4). We describe a clinical case presenting bilateral sensorineural hearing loss and enlarged vestibular aqueduct in which a novel homozygous SLC26A4 mutation was identified. Despite a late diagnosis of hearing loss, a peculiar rehabilitation therapy strategy was identified that provided excellent results.

The characteristics of social maturity in infants and children with cochlear implants in China

OBJECTIVE

The primary aim of the current study was to examine the social maturity of infants and children with cochlear implants in China. A secondary aim was to document the associated information using a General Condition Questionnaire for further cohort study in this population.

MATERIALS AND METHODS

This is a retrospective cross-sectional observational study and a pilot study. Between July and December 2017, data from all implantees between the ages of 6 months and 14 years who presented to the Hearing and Speech Center of Shanghai Ninth People's Hospital for mapping were collected. There were 119 non-overlapping cases in total. Data were collected via the Infants-Junior Middle School Students' Social-Life Abilities Scale (S-M scale) and a structured General Condition Questionnaire. The S-M scale was used for social adaptability measurement for children aged between 6 months to 14 yearsold. The General Condition Questionnaire, which was completed by the parents or primary caregivers of the implantees, gathered 3 aspects of personal information: the patient's history of hearing loss, personal history of rehabilitation and their past medical history.

RESULTS

Results showed that in 119 cases, 89 implantees (74.8%) were at or above a normal social maturity level. Thirty implantees (25.2%) scored lower than normal on the S-M standard score. Spearman's rank correlation indicated that the age at which hearing loss was noticed, the age of initial rehabilitation and the age at implantation were significantly correlated with the patients' scores on the S-M scale.

CONCLUSION

In summary, most of the cochlear implantees showed normal social maturity, with the exception of 25.2% of implantees who performed at a lower level than their normal hearing peers. These findings suggest potential targets to investigate in future cohort studies in cochlear implantees.

Sensorineural Hearing Loss in the Nonimplanted Ear Following Cochlear Implantation in a Patient With Bilateral Enlarged Vestibular Aqueducts

OBJECTIVE

To document the case of a patient with bilateral enlarged vestibular aqueducts who experienced sensorineural hearing loss in the nonimplanted ear following unilateral cochlear implantation complicated by perilymph gusher requiring lumbar drain insertion and to highlight the need to counsel regarding the risk of potential hearing loss to the contralateral ear when preparing for cochlear implants in the setting of inner ear malformations.

PATIENTS

One patient with bilateral enlarged vestibular aqueducts in a tertiary referral center.

INTERVENTION(S)

Cochlear implantation complicated by perilymph gusher requiring lumbar drain insertion.

MAIN OUTCOME MEASURE(S)

Bone conduction hearing thresholds, word recognition scores.

RESULTS

The patient underwent unilateral cochlear implantation, which was complicated by a perilymphatic gusher and necessitated placement of an intraoperative lumbar drain. On postoperative day 1, the patient reported hearing loss in the opposite ear. The word recognition score in the contralateral ear dropped from 24% at preimplantation to 8% at 2-weeks postimplantation, and did not improve at 6 months postimplantation. Moreover, the bone conduction threshold at 1 kHz worsened from 20 dB preoperatively to no response at 75 dB (the limit of the testing equipment) at 2-weeks postoperatively and only partially improved to 40 dB at 6 months postimplantation.

CONCLUSION

As patients with inner ear malformations potentially have direct high-pressure anatomical connections between the perilymphatic spaces and the cerebrospinal fluid, they are at risk of hearing loss in the nonimplanted ear during cochlear implantation. This case highlights the need for potential additional patient counseling regarding this risk in the nonimplanted ear.