Electrophysiologic and Behavioral Outcomes of Cochlear Implantation in Children With Auditory Nerve Hypoplasia

Intraoperative EABR Testing Predicts Strength of Cochlear Implant Stimulation Optimized After Long-Term Use in Pediatric Malformation Ears

OBJECTIVE

This study focused on the intensities of cochlear implant (CI) stimulation in pediatric CI users with inner ear malformation or cochlear nerve deficiency (CND). In this population, CI programming is difficult because a large intensity of CI stimulation is required to achieve sufficient hearing, but the excess CI stimuli often induce facial nerve stimulation. We aimed to assess whether the results of intraoperative electrically evoked auditory brainstem responses (EABRs) testing predict maximum current levels of CI stimuli (cC levels) optimized by a behavioral-based method after long-term CI use.

STUDY DESIGN

A retrospective case review.

SETTING

A tertiary referral CI center.

PATIENTS

A total of 116 ears with malformations (malformation group) and 63 control ears (control group) from patients younger than 18 years who received CI. The malformation group comprised 23 ears with a common cavity (CC), 26 with incomplete partition type 1 (IP-1), 26 with incomplete partition type 2 (IP-2), and 41 with CND.

INTERVENTIONS

Diagnostic.

MAIN OUTCOME MEASURES

Correlation between intraoperative EABR results and cC levels determined by the behavioral-based CI programming after long-term CI use.

RESULTS

The CC, IP-1, and CND ears required significantly larger cC levels than the IP-2 ears and control groups. However, the cC levels increased to reach the plateau 1 year after surgery in all groups. Among the malformation group, 79 ears underwent intraoperative EABR testing. Greater than 80% of the CC, IP-1, and IP-2 ears and 54.8% of the CND ears exhibited evoked wave V (eV) and were included in the eV-positive category. Myogenic responses but no eV were observed in 18.2, 15.0, and 35.5% of the CC, IP-1, and CND ears, defined as the myogenic category. No eV or myogenic response was elicited in 9.7% of the CND ears. We focused on minimum current levels that elicited eV (eV levels) in the eV-positive category and maximum current levels that did not elicit any myogenic responses (myogenic levels) in the myogenic category. A significant relationship was detected between the eV levels and the cC levels. When analyzed in each malformation type, the eV levels significantly correlate with the cC levels in the CC and CND ears but not in the IP-1 and IP-2 ears, probably because of slight variation within the IP-1 group and the small number of the IP-2 group. The myogenic category did not show a significant relationship between the myogenic levels and cC levels, but the cC levels were similar to or smaller than the myogenic levels in most ears.

CONCLUSIONS

This study confirmed that intraoperative EABR testing helps predict the optimal cC levels in malformation ears. EABR-based CI programming immediately after cochlear implantation, followed by behavioral-based CI programming, may allow us to achieve early postoperative optimization of CI maps even in young children with severe malformations.

Detection of Reduced Diameter of the Cochlear Nerve in Long-term Deaf Patients Quantified With Semiautomatic Measurement of Nerve Cross-sectional Area Using 3T MRI Data

Hypothesis

High-resolution parallel transmit T2 sampling perfection with application optimized contrast using different flip angle evolution sequence with improved edge discrimination and semiautomatic determination of nerve cross-sectional area (CSA) can be used to evaluate nerve degeneration in the inner auditory canal (IAC) in long-term deaf patients.

Background

In patients with hearing loss, temporal bone MRI is routinely acquired to evaluate the morphology of the nerves within the IAC. Earlier studies have shown that the diameter of the cochlear nerve can be used as prognostic marker for the auditory performance after cochlear implantation in postlingually deaf patients.

Methods

Eighty-two consecutive MRI scans were analyzed using a semiautomatic tool to measure CSA of cranial nerves in the IAC. Results were correlated with patient history and audiology testing as well as with age and gender.

Results

There was a significant reduced CSA of the cochlear nerve in ears with moderate-to-profound hearing loss and deafness compared with ears with normal hearing, but no significant difference in ears with mild-to-moderate hearing loss compared with normal hearing. In detail, normal hearing ears had a CSA of 1.23 ± 0.11 mm2, whereas ears with pantonal hearing loss of more than 40 dB had 1.02 ± 0.05 mm2 (P = 0.026). Maximal CSA of the facial nerve was not different among all groups (average, 1.04 mm2 ± 0.03; linear regression, P = 0.001) and stable with age. However, vestibular nerve CSA decreased significantly with age (average, 1.78 ± 0.05 mm2; linear regression, P = 0.128).

Conclusions

In long-term deaf patients, smaller the diameter of cochlear nerve is the more severe the hearing loss is. The new semiautomatic tool can primarily be used to assess nerve diameter and possibly determine ears with nerve degeneration.

Early cochlear implantation for children with single sided deafness

OBJECTIVES

Single-sided deafness (SSD) can have consequences for a child's language, educational, and social development. A cochlear implant (CI) is the only device which can restore true binaural hearing, yet they are only approved for children with (SSD) over the age of five in the United States. Reports on speech perception outcomes for children implanted at a younger age are limited. The present study aims to examine the effects of age at implantation, duration of deafness, hearing loss etiology, and presence of additional disabilities on device usage and speech perception outcomes.

METHODS

A retrospective chart review was used to examine demographics and speech perception outcomes for 18 children implanted at age five or younger.

RESULTS

Speech perception results were highly variable, with some children deriving significant benefit and others demonstrating no sound awareness through the implant alone. Age at implantation and duration of deafness did not have a clear impact on outcomes. Device usage was low in many children, often those with anatomical abnormalities such as a hypoplastic cochlear nerve. There are challenges to assessing speech perception in young children with SSD, leading to a lack of standardized outcome measures.

CONCLUSIONS

Early CI for children with SSD may improve speech perception, but benefit is not guaranteed. Candidacy evaluation should consider both medical and audiological factors, in addition to the degree of family support and realistic expectations. Caution is especially warranted in children with significant anatomical anomalies.

Cochlear implantation programming characteristics and outcomes of cochlear nerve deficiency

PURPOSE

Due to the specificity of cochlear implantation (CI) programming parameters and outcomes in cochlear nerve deficiency (CND) patients, this study aimed to investigate the correlation between programming parameters and outcomes and further compare the difference between normal and CND groups.

METHODS

Ninety (95 ears) CND patients (normal cochlea, 39; malformed cochlea, 56) and seventy-nine (81 ears) normal cochlea patients who underwent CI surgery with either Med-El or Cochlear devices were included. The programming parameters and outcomes evaluated by the questionnaires were collected and compared among the normal CND, malformed CND, and normal groups in the two device groups, and their correlation was analyzed.

RESULTS

In the CND group, a reduced stimulation rate, higher pulse width, and triphasic pulse were needed in some cases. The stimulus levels of the CND group were significantly higher than that of the normal group (p < 0.05), but the outcomes of the CND group were significantly worse than that of the normal group (p < 0.05), and the stimulus level was significantly correlated with the outcomes (p < 0.05). However, there was no difference between normal and malformed CND groups. The non-auditory response was observed in the CND group, especially the ones with malformations.

CONCLUSION

The CI programming parameters of some CND patients need to be adjusted, and a slower stimulation rate and higher pulse width are required sometimes. CND patients need a higher stimulus level than normal patients but their outcomes are poorer. Non-auditory response should be noticed in CND patients during programming.

Audiological characteristics and cochlear implant outcome in children with cochlear nerve deficiency

Objectives

This study aimed to examine the audiological characteristics and validity of predicting outcomes of cochlear implants (CIs) in children with cochlear nerve deficiency (CND) based on the internal auditory meatus (IAM) nerve grading system.

Methods

The audiological characteristics of 188 ears in 105 children diagnosed with CND were analyzed based on the IAM nerve grading system. In addition, 42 children with CND who underwent CI were also divided into four groups based on the system, and their auditory and speech performance at baseline (preoperative) and 6, 12, and 24 months after CI were analyzed and compared with those of the control group (n = 24) with a normal cochlear nerve (CN) and CI.

Results

The audiological test results showed no significant differences among the four CND groups in terms of elicited rates of distortion product otoacoustic emission (DPOAE) (p = 1.000), auditory brainstem response (ABR) (p = 0.611), and cochlear microphonic (CM) (p = 0.167). Hearing in the CND IV group was significantly better than that in the CND I group (p < 0.05). In children with CI, the auditory and speech performance of the control group was significantly higher than all CND groups from 6 to 24 months (p < 0.05) and 12 to 24 months (p < 0.05), respectively. Meanwhile, there were no significant differences between each pair group in the four CND groups (p > 0.05).

Conclusion

Children with CND, including those in whom the CN was not visualized by MRI, can benefit from CI. Additionally, the IAM nerve grading system could not predict the outcomes of CI in children with CND.

Endoscopic Repair of Round Window Cochleocele

OBJECTIVE

To describe the novel presentation, implications, and endoscopic management of a congenital round window cochleocele.

PATIENT

A 16-month old girl with profound hearing loss from bilateral incomplete partition type 1 (IP1) anomaly of the cochlea plus left-sided cochlear nerve aplasia and cochleocele.

INTERVENTION

Anomalies were identified with computed tomographic scanning and magnetic resonance imaging during cochlear implant candidacy assessment. While under general anesthesia for right-sided cochlear implantation, the cochleocele was removed and packed with temporalis fascia using transcanal endoscopic ear surgery. The endoscope was held by an assistant while the surgeon packed the round window using a two-handed technique to counter the gush of cerebrospinal fluid.

RESULTS

The child made an uneventful recovery with no cerebrospinal fluid leak or meningitis.

CONCLUSIONS

Cochleocele can protrude through the round window of a cochlea with incomplete partition type 1 anomaly. An increased risk of meningitis secondary to acute otitis media is expected given the known risk from cochleocele arising through a stapes footplate fistula. Care should be taken to check for the presence of a cochleocele in hearing loss from congenital malformations involving the basal turn of the cochlea on imaging and also at the time of cochlear implant surgery. Repair should be considered at the first opportunity to prevent meningitis. If early cochlear implant surgery is not feasible or appropriate (as, for example, with cochlear nerve aplasia), transcanal endoscopic ear surgery provides good access for a low-morbidity approach.

Imaging and audiological features of children with cochlear nerve deficiency

Objective: Cochlear nerve deficiency (CND) accounts for 10-19% of hearing loss in children; this study investigated the imaging and audiological features of 25 CND children. Methods: A total of 563 children with an unpassed automatic auditory brainstem response were diagnosed with hearing loss in our department between December 2018 and December 2021, of which, the imaging and audiological features of 25 children (25/563, 4.4%) diagnosed with a CND were reviewed. Results: Twenty-one (21/25, 84.0%) CND children had unilateral deafness, and 4 cases of bilateral deafness. All deaf ears were diagnosed as severe hearing loss due to an auditory brainstem response. CM waves were recorded in 8 cases and DPOAE in 3 cases, suggesting the audiological characteristics of auditory neuropathy spectrum disorders (ANSD). MRI results indicated 23 cases had small cochlear nerves and 2 cases had absent cochlear nerves. No genetic mutations were identified in the 25 CND children. Conclusions: Most CND children had unilateral hearing loss; therefore, high-resolution MRI imaging of the internal auditory canal should be performed to detect the auditory nerve in children with severe hearing loss. Some CND children had characteristics of ANSD.

Pediatric Single-Sided Deafness: A Review of Prevalence, Radiologic Findings, and Cochlear Implant Candidacy

OBJECTIVE

To characterize the prevalence, imaging characteristics, and cochlear implant candidacy of pediatric patients with single-sided deafness (SSD).

METHODS

An audiometric database of patients evaluated at a large tertiary academic medical center was retrospectively queried to identify pediatric patients (<18 years old) with SSD, defined as severe to profound sensorineural hearing loss in one ear and normal hearing in the other. Medical records of identified patients were reviewed to characterize the prevalence, etiology, and cochlear implant candidacy of pediatric patients with SSD.

RESULTS

We reviewed audiometric data obtained from 1993 to 2018 for 52,878 children at our institution. 191 (0.36%) had the diagnosis of SSD. Cochlear nerve deficiency (either hypoplasia or aplasia) diagnosed on MRI and/or CT was the most common etiology of SSD and was present in 22 of 88 (25%) pediatric SSD patients with available imaging data. 70 of 106 (66%) pediatric SSD patients with available imaging had anatomy amenable to cochlear implantation.

CONCLUSIONS

Pediatric SSD is a rare condition and the most common etiology based on radiology is cochlear nerve deficiency. High resolution imaging of the temporal bone is essential to determine cochlear nerve morphology prior to consideration of cochlear implantation.

A Study of Outcome of Pediatric Cochlear Implantation in Patients with Cochleovestibular Nerve Deficiency

OBJECTIVES

A cochleovestibular nerve deficiency (CVND) could compromise stimulation of nerve by electrical pulses delivered from a cochlear implant, thereby hindering activity along auditory pathway. The evaluation of children with congenital hearing loss with a high-resolution magnetic resonance imaging is presently the investigative modality of choice to diagnose CVND. The aim of this study was to determine the outcomes in pediatric cochlear implant recipients with a diagnosis of CVND. The objectives included (1) to study the prevalence of CVND among children with prelingual congenital severe to profound hearing loss; (2) to assess post cochlear implantation (CI) outcomes in children with CVND using categories of auditory performance (CAP), speech intelligibility rating (SIR), and cortical auditory evoked potentials (CAEPs); and (3) to propose a management protocol for these children.

MATERIALS AND METHODS

All CI procedures performed during the study period in children 5 years or younger were included in study. All patients who were older than 5 years or had syndromic associations, multiple disabilities, second side or revision CI were excluded from the study. Children with unilateral cochleovestibular nerve aplasia and all other cases of CVND (type IIa and IIb) were advised to undergo CI on side with more radiologically robust nerve and/or cochlea anatomy. Children with bilateral CVND were included in group A, and age-matched cochlear implant candidates with normal cochleovestibular nerve anatomy were included in group B for statistical comparison of outcomes.

RESULTS

In group A, post CI CAP and SIR, CAEP amplitude and latency at 12 months showed statistically significant difference (p<0.05) compared with preoperative values. However, mean score of CAEP latency and amplitude and SIR score was worse for group A compared with group B at 12 months, which was statistically significant (p<0.05).

CONCLUSION

This study supports the fact that CI is a viable option to be offered in children with CVND (type IIa and IIb) for the development of auditory perception and speech.

The limitation of risk factors as a means of prognostication in auditory neuropathy spectrum disorder of perinatal onset

OBJECTIVE

The management of hearing loss due to auditory neuropathy spectrum disorder (ANSD) in neonates and infants is challenging because speech and language development prognosis cannot be directly inferred from early audiometric hearing thresholds. Consequently, appropriate intervention with hearing aids or cochlear implantation (CI) can be delayed. Our objective was to determine whether any features of patient history could be used to identify CI candidates with ANSD at an earlier age.

METHOD

A database was maintained over 11 years to monitor cases of perinatal onset ANSD. Risk factors associated with the perinatal time period considered pertinent to hearing outcomes were assessed, including prematurity, birth weight, APGAR score, ototoxic drugs, and hyperbilirubinemia. Children with cochlear nerve aplasia and genetic mutations were excluded. Hearing outcome was determined according to mode of auditory rehabilitation beyond 30 months of age: A) no hearing device; B) hearing aid; C) CI.

RESULTS

Of twenty-eight children with ANSD, nine (32%) had behavioural thresholds and language development sufficient to require no assistive device, 9 (32%) were fitted with hearing aids and 10 (36%) had CIs. The average age at CI (3.45 ± 2.07 years) was significantly older than the age at CI of other children in our program with prelingual hearing loss (2.05 ± 1.14 years; p = 0.01 Mann-Witney U Test). None of the putative risk factors for hearing loss reliably predicted the need for subsequent CI.

CONCLUSION

The small sample size in this study is sufficient to confirm that clinical history alone does not reliably predict which young children with perinatal-onset ANSD will require CI. Consequently, timing for CI remains delayed in these children, potentially affecting speech and language outcome. The pathogenesis of perinatal-onset ANSD remains undetermined and novel means of assessment are required for prognostication in affected infants.

Hearing and speech benefits of cochlear implantation in children: A review of the literature

Cochlear implantation is a safe and reliable treatment for children with severe to profound hearing loss. The primary benefit of these medical devices in children is the acquisition of hearing, which promotes development of spoken language. The present paper reviews published literature demonstrating predictive effects of a number of factors on acquisition of hearing development and speech recognition. Of the many variables that contribute to an individual child's development after implantation, age at implantation, the presence of medical comorbidities, social determinants of health, and the provision of bilateral versus unilateral hearing are those that can vary widely and have consistently shown clear impacts. Specifically, age of implantation is crucial to reduce effects of deafness on the developing auditory system and capture the remarkable plasticity of early development. Language development after cochlear implantation requires therapy emphasizing hearing and oral communication, education, and other support which can be influenced by known social determinants of health; specifically, outcomes in children decline with reductions in socioeconomic status and levels of parental education. Medical co-morbidities also slow rates of progress after cochlear implantation. On the other hand, benefits of implantation increase in children who are provided with access to hearing from both ears. In sum, cochlear implants promote development of hearing in children and the best outcomes are achieved by providing early access to sound in both ears. These benefits can be limited by known social determinants of health which restrict access to needed support and medical comorbidities which add further complexity in care and outcome.

Assessment of the Clinical Benefit of Imaging in Children With Unilateral Sensorineural Hearing Loss: A Systematic Review and Meta-analysis

Importance

Imaging used to determine the cause of unilateral sensorineural hearing loss (USNHL) in children is often justified by the high likelihood of detecting abnormalities, which implies that these abnormalities are associated with hearing loss and that imaging has a positive contribution to patient outcome or well-being by providing information on the prognosis, hereditary factors, or cause of hearing loss.

Objectives

To evaluate the diagnostic yield of computed tomography (CT) and magnetic resonance imaging (MRI) in children with isolated unexplained USNHL and investigate the clinical relevance of these findings.

Evidence Review

Cochrane Library, Embase, PubMed, and Web of Science databases were searched for articles published from 1978 to 2017 on studies of children with USNHL who underwent CT and/or MRI of the temporal bone. Two authors (F.G.R. and E.N.B.P.) independently extracted information on population characteristics, imaging modality, and the prevalence of abnormalities and assessed the studies for risk of bias. Eligibility criteria included studies with 20 or more patients with USNHL who had CT and/or MRI scans, a population younger than 18 years, and those published in English.

Main Outcomes and Measures

The pooled prevalence with 95% CI of inner ear abnormalities grouped according to finding and imaging modality.

Findings

Of 1562 studies, 18 were included with a total of 1504 participants included in the analysis. Fifteen studies were consecutive case studies and 3 were retrospective cohort studies. The pooled diagnostic yield for pathophysiologic relevant findings in patients with unexplained USNHL was 37% for CT (95% CI, 25%-48%) and 35% for MRI (95% CI, 22%-49%). Cochleovestibular abnormalities were found with a pooled frequency of 19% for CT (95% CI, 14%-25%) and 16% for MRI (95% CI, 7%-25%). Cochlear nerve deficiency and associated cochlear aperture stenosis had a pooled frequency of 16% for MRI (95% CI, 3%-29%) and 44% for CT (95% CI, 36%-53%), respectively. Enlarged vestibular aqueduct (EVA) was detected with a pooled frequency of 7% for CT and 12% for MRI in children with USNHL.

Conclusions and Relevance

Imaging provided insight into the cause of hearing loss in a pooled frequency of about 35% to 37% in children with isolated unexplained USNHL. However, none of these findings had therapeutic consequences, and imaging provided information on prognosis and hereditary factors only in a small proportion of children, namely those with EVA. Thus, there is currently no convincing evidence supporting a strong recommendation for imaging in children who present with USNHL. The advantages of imaging should be carefully balanced against the drawbacks during shared decision making.

Responsiveness of the Electrically Stimulated Cochlear Nerve in Children With Cochlear Nerve Deficiency

OBJECTIVES

This study aimed to (1) investigate the responsiveness of the cochlear nerve (CN) to a single biphasic-electrical pulse in implanted children with cochlear nerve deficiency (CND) and (2) compare their results with those measured in implanted children with normal-size CNs.

DESIGN

Participants included 23 children with CND (CND1 to CND23) and 18 children with normal-size CNs (S1 to S18). All subjects except for CND1 used Cochlear Nucleus cochlear implants with contour electrode arrays in their test ears. CND1 was implanted with a Cochlear Nucleus Freedom cochlear implant with a straight electrode array in the test ear. For each subject, the CN input/output (I/O) function and the refractory recovery function were measured using electrophysiological measures of the electrically evoked compound action potential (eCAP) at multiple electrode sites across the electrode array. Dependent variables included eCAP threshold, the maximum eCAP amplitude, slope of the I/O function, and time-constants of the refractory recovery function. Slopes of I/O functions were estimated using statistical modeling with a sigmoidal function. Recovery time-constants, including measures of the absolute refractory period and the relative refractory period, were estimated using statistical modeling with an exponential decay function. Generalized linear mixed-effect models were used to evaluate the effects of electrode site on the dependent variables measured in children with CND and to compare results of these dependent variables between subject groups.

RESULTS

The eCAP was recorded at all test electrodes in children with normal-size CNs. In contrast, the eCAP could not be recorded at any electrode site in 4 children with CND. For all other children with CND, the percentage of electrodes with measurable eCAPs decreased as the stimulating site moved in a basal-to-apical direction. For children with CND, the stimulating site had a significant effect on the slope of the I/O functions and the relative refractory period but showed no significant effect on eCAP threshold and the maximum eCAP amplitude. Children with CND had significantly higher eCAP thresholds, smaller maximum eCAP amplitudes, flatter slopes of I/O functions, and longer absolute refractory periods than children with normal-size CNs. There was no significant difference in the relative refractory period measured in these two subject groups.

CONCLUSIONS

In children with CND, the functional status of the CN varied along the length of the cochlea. Compared with children with normal-size CNs, children with CND showed reduced CN responsiveness to electrical stimuli. The prolonged CN absolute refractory period in children with CND might account for, at least partially, the observed benefit of using relatively slow pulse rate in these patients.

Efficacy of a selective imaging paradigm prior to pediatric cochlear implantation

OBJECTIVES/HYPOTHESIS

There is no consensus on the necessary preoperative imaging in children being evaluated for cochlear implantation (CI). Dual-imaging protocols that implement both magnetic resonance imaging (MRI) and high resolution computed tomography (HRCT) create diagnostic redundancy in the face of potentially unnecessary radiation and anaesthetic exposure. The objectives of the current study were to examine the efficacy of an MRI-predominant with selective HRCT imaging protocol.

STUDY DESIGN

Retrospective review.

METHODS

The protocol was implemented over a 4-year period, during which HRCT was obtained in addition to MRI only if specific risk factors on clinical assessment were identified or if imaging findings in need of further evaluation were detected on initial MRI evaluation. Retrospective review of operative reports and prospective review of imaging were performed; anesthetic exposure and costing information were also obtained.

RESULTS

Of the 240 patients who underwent assessment, seven (2.9%) had combined HRCT and MRI performed concurrently based on initial clinical assessment, 15 (6.3%) underwent HRCT based on imaging anomalies found on MRI, and MRI alone was ordered for the remaining 218 (90.1%). All patients were implanted without complication. Overall, radiation exposure, general anesthesia (GA), and healthcare costs were reduced.

CONCLUSIONS

MRI alone can be used in the vast majority of cases for preoperative evaluation of pediatric CI candidates resulting in a significant reduction in healthcare costs, radiation, and GA exposure in children. The additional need for HRCT occurs in a small proportion and can be predicted up front on clinical assessment or on initial MRI.

LEVEL OF EVIDENCE

4 Laryngoscope, 129:2627-2633, 2019.

Appropriate Imaging Modality for the Etiologic Diagnosis of Congenital Single-Sided Deafness in Children

We aimed to compare the diagnostic yield between temporal bone computed tomography (TBCT) and internal auditory canal MRI (IAC MRI) for the etiologic diagnosis of children with congenital single-sided deafness (SSD) and the evaluation of cochlear implant (CI) candidacy. In the original cohort, 24 subjects with congenital SSD were enrolled and underwent both TBCT and IAC MRI. We recruited an additional 22 consecutive infants with congenital SSD (the supplementary cohort) and evaluated in particular the cochlear nerve (CN) integrity using IAC MRI. Cochlear nerve deficiency (CND) was classified as ‘absent’, ‘small’, and ‘indeterminate’ via mutual comparison between optical and parameters based on the MRI results. The most common etiologies were CND in the original cohort (19 out of 24). Notably, accurate evaluations of CN status (‘small CN’ = 2, ‘indeterminate CN’ = 2), inner ear malformations, and brain abnormalities were possible only with MRI. The ‘indeterminate CN’ tended to be more frequently detected in SSD ears than in unaffected ears. MRI appeared to be more accurate than TBCT in a meticulous differentiation of CN, which is crucial for the selection of appropriate CI candidacy among congenital SSD children. Additionally, we introduced the novel concept of ‘indeterminate CN’, of which the causal relationship with SSD awaits confirmation.

Children with unilateral cochlear nerve canal stenosis have bilateral cochleovestibular anomalies

OBJECTIVES/HYPOTHESIS

To investigate the cochleovestibular apparatus bilaterally in children with isolated unilateral bony cochlear nerve canal (bCNC) stenosis.

STUDY DESIGN

Retrospective review.

METHODS

Imaging studies of children with unilateral bCNC stenosis (<1.0 mm) on computed tomography imaging (N = 36) were compared with controls imaged due to trauma without temporal bone injury (N = 32). Twenty-six measurements were obtained in each ear, assessing the bony internal auditory canal (IAC), cochlea, and vestibular end-organs, and were analyzed using one-way analysis of variance for intersubject comparisons and paired t tests for intrasubject comparisons with a Bonferroni adjustment for multiple comparisons (P = .0006).

RESULTS

Patients with bCNC stenosis had a smaller IAC (P < .000) and cochlea (P < .000) on the stenotic side as compared with controls. Although the vestibular end-organ was also smaller in bCNC ears, this difference was not significant. The contralateral ear also had a smaller bCNC (P < .000) and cochlea (P < .000) as compared with controls, although to a lesser degree than the stenotic side.

CONCLUSIONS

Children with unilateral bCNC stenosis have abnormal biometry of both the cochlea and the vestibular end-organ in the affected and the normal contralateral ear as compared with controls.

LEVEL OF EVIDENCE

3b Laryngoscope, 129:2403-2408, 2019.

Assessing the Benefit-Risk Profile for Pediatric Implantable Auditory Prostheses

BACKGROUND/AIMS

Children with congenital cochleovestibular abnormalities associated with profound hearing loss have few treatment options if cochlear implantation does not yield benefit. An alternative is the auditory brainstem implant (ABI). Regulatory authority device approvals currently include a structured benefit-risk assessment. Such an assessment, for regulatory purposes or to guide clinical decision making, has not been published, to our knowledge, for the ABI and may lead to the design of a research program that incorporates regulatory authority, family, and professional input.

METHODS

Much structured benefit-risk research has been conducted in the context of drug trials; here we apply this approach to device studies. A qualitative framework organized benefit (speech recognition, parent self-report measures) and risk (surgery- and device-related) information to guide the selection of candidates thought to have potential benefit from ABI.

RESULTS

Children with cochleovestibular anatomical abnormalities are challenging for appropriate assessment of candidacy for a cochlear implant or an ABI. While the research is still preliminary, children with an ABI appear to slowly obtain benefit over time. A team of professionals, including audiological, occupational, and educational therapy, affords maximum opportunity for benefit.

CONCLUSIONS

Pediatric patients who have abnormal anatomy and are candidates for an implantable auditory prosthetic require an individualized, multisystems review. The qualitative benefit-risk assessment used here to characterize the condition, the medical need, potential benefits, risks, and risk management strategies has revealed the complex factors involved. After implantation, continued team support for the family during extensive postimplant therapy is needed to develop maximum auditory skill benefit.

Outcomes after cochlear implant provision in children with cochlear nerve hypoplasia or aplasia

INTRODUCTION

Cochlear nerve aplasia or hypoplasia is found in up to a half of patients with unilateral or bilateral hearing loss. There is an ongoing discussion regarding the indication of cochlear implants for hearing rehabilitation in cases with radiologically-defined aplasia or hypoplasia of the cochlear nerve in those patients, especially in children. At present there is conflicting evidence whether the audiological outcomes of those children with a CI are comparable to those of children with a CI and a radiologically-normal cochlear nerve. The primary aim of this study was to assess the audiological abilities before and after CI provision in children with cochlear nerve hypoplasia or aplasia. Additionally, we aimed to determine if audiological outcomes differed in children with aplasia from those with hypoplasia. Such data should be helpful in determining if CI provision is appropriate for such children.

METHODS

This retrospective study presents 7 children who were diagnosed with cochlear nerve aplasia or hypoplasia and received a CI. The pre- and postoperative audiological performance and the hearing and speech development of the children were examined.

RESULTS

4 children were unilateral CI users and 3 were bilateral CI users. Hearing reactions could be detected in all children. Already at first fitting, prompt responses and reactions to songs were observed. The aided thresholds in free field in children with hypoplasia were between 30 and 60 dB. Even in children with aplasia, the results in free field with CI averaged between 30 and 70 dB. Therefore the aided thresholds in children with hypoplasia and in children with aplasia of the CN are similar. It could be demonstrated that hearing reactions improve with the long term use of the implant. Improvement in general development could be observed in all children despite the very heterogeneous conditions and the accompanying handicaps.

CONCLUSION

The results of this study support the hypothesis that children with radiologically-defined CN hypoplasia or aplasia and detectable responses to electrical or acoustical stimuli can improve their sound detection thresholds and their awareness of sound when provided with a CI.

Progression of Unilateral Hearing Loss in Children With and Without Ipsilateral Cochlear Nerve Canal Stenosis: A Hazard Analysis

OBJECTIVE

To investigate the risk of hearing loss progression in each ear among children with unilateral hearing loss associated with ipsilateral bony cochlear nerve canal (BCNC) stenosis.

SETTING

Tertiary pediatric referral center.

PATIENTS

Children diagnosed with unilateral hearing loss who had undergone temporal bone computed tomography imaging and had at least 6 months of follow-up audiometric testing were identified from a prospective audiological database.

INTERVENTIONS

Two pediatric radiologists blinded to affected ear evaluated imaging for temporal bone anomalies and measured bony cochlear canal width independently. All available audiograms were reviewed, and air conduction thresholds were documented.

MAIN OUTCOME MEASURE

Progression of hearing loss was defined by a 10 dB increase in air conduction pure-tone average.

RESULTS

One hundred twenty eight children met inclusion criteria. Of these, 54 (42%) had a temporal bone anomaly, and 22 (17%) had ipsilateral BCNC stenosis. At 12 months, rates of progression in the ipsilateral ear were as follows: 12% among those without a temporal bone anomaly, 13% among those with a temporal bone anomaly, and 17% among those with BCNC stenosis. Children with BCNC stenosis had a significantly greater risk of progression in their ipsilateral ear compared with children with no stenosis: hazard ratio (HR) 2.17, 95% confidence interval (CI) (1.01, 4.66), p value 0.046. When we compared children with BCNC stenosis to those with normal temporal bone imaging, we found that the children with stenosis had nearly two times greater risk estimate for progression, but this difference did not reach significance, HR 1.9, CI (0.8, 4.3), p = 0.1. No children with BCNC stenosis developed hearing loss in their contralateral year by 12 months of follow-up.

CONCLUSION

Children with bony cochlear nerve canal stenosis may be at increased risk for progression in their ipsilateral ear. Audiometric and medical follow-up for these children should be considered.

Programming characteristics of cochlear implants in children: effects of aetiology and age at implantation

OBJECTIVE

We investigated effects of aetiology and age at implantation on changes in threshold (T) levels, comfortable (C) levels and dynamic range (DR) for cochlear implants (CIs) in children over the first five years of life.

DESIGN

Information was collected at 6 months post-activation of CIs, and at 3 and 5 years of age.

STUDY SAMPLE

One hundred and sixty-one children participating in the Longitudinal Outcomes of Children with Hearing Impairment (LOCHI) study.

RESULTS

Children with neural and structural cochlear lesions had higher T-levels and C-levels as compared to those without these conditions. Parameter settings varied from manufacturer's defaults more often in the former than in the latter group. Investigation of the effect of age at implantation for children without neural and structural cochlear lesions showed that those implanted at ≤12 months of age had higher T-levels and narrower DR at 6 months post-activation, as compared to the later-implanted group. For both early- and later-implanted groups, the C-levels at 6 months post-activation were lower than those at age 3 and 5 years. There were no significant differences in T-levels, C-levels, or DR between age 3 and 5 years.

CONCLUSIONS

Aetiology and age at implantation had significant effects on T-levels and C-levels.

Cochlear Nerve Aplasia and Hypoplasia: Predictors of Cochlear Implant Success

Objective

To identify factors predicting performance outcomes following cochlear implantation in patients with cochlear nerve aplasia or hypoplasia.

Data Sources

Individual patient data extracted from published case series and reports.

Review Methods

The MEDLINE database, Cochrane Library, Embase, Web of Science, and Google Scholar were queried for “cochlear implant” in conjunction with “aplasia” or “hypoplasia” between 1985 and 2015. Eighteen studies were included describing 97 subjects with individual postimplant auditory data. Postimplant performance was categorized as follows: level 1, nonstimulation/minimal detection; level 2, improved detection; level 3, closed-set speech perception; or level 4, open-set speech perception. The subjects achieving speech perception (levels 3 and 4) were descriptively compared with those who did not.

Results

Subjects with a hypoplastic cochlear nerve on magnetic resonance imaging had higher reported rates of achieving speech perception than those with an aplastic nerve. Subjects with syndromic medical comorbidities had higher reported rates of nonstimulation than nonsyndromic subjects. The data showed that some children with an aplastic cochlear nerve or those with partial electrode insertion could obtain levels of speech discrimination. Reporting of patient characteristics and auditory outcomes was extremely variable across studies.

Conclusion

As previously shown, cochlear implant in patients with cochlear nerve aplasia or hypoplasia can provide meaningful hearing for select patients. The current study suggests that presence of a cochlear nerve on magnetic resonance imaging and lack of comorbid medical syndrome are associated with better auditory outcomes in such patients. Future efforts to report individual data in a consistent manner may allow better determination of predictive factors.

A Prospective Longitudinal Study of U.S. Children Unable to Achieve Open-Set Speech Recognition 5 Years After Cochlear Implantation

OBJECTIVE

To identify characteristics associated with the inability to progress to open-set speech recognition in children 5 years after cochlear implantation.

STUDY DESIGN

Prospective, longitudinal, and multidimensional assessment of auditory development for 5 years.

SETTING

Six tertiary cochlear implant (CI) referral centers in the United States.

PATIENTS

Children with severe-to-profound hearing loss who underwent implantation before age 5 years enrolled in the Childhood Development after Cochlear Implantation study, categorized by level of speech recognition ability.

INTERVENTION(S)

Cochlear implantation before 5 years of age and annual assessment of emergent speech recognition skills.

MAIN OUTCOME MEASURE(S)

Progression to open-set speech recognition by 5 years after implantation.

RESULTS

Less functional hearing before implantation, older age at onset of amplification, lower maternal sensitivity to communication needs, minority status, and complicated perinatal history were associated with the inability to obtain open-set speech recognition by 5 years.

CONCLUSION

Characteristics of a subpopulation of children with CIs associated with an inability to achieve open-set speech recognition after 5 years of CI experience were investigated. These data distinguish pediatric CI recipients at risk for poor auditory development and highlight areas for future interventions to enhance support of early implantation.

Auditory neuropathy spectrum disorder (ANSD) and cochlear implantation

We discuss issues related to cochlear implantation in children with auditory neuropathy spectrum disorder (ANSD). We describe the varied nature of this disease category including the numerous potential causes of auditory neuropathy. The most prevalent etiology for infants with ANSD is associated with prolonged neonatal intensive care unit (NICU) stay. We discuss the potential contribution of cochlear hypoxia to this etiology. The second part of this review describes in detail our own experience at the Hospital for Sick Children in Toronto, with cochlear implantation of children diagnosed with ANSD. We outline the detection, diagnosis, and referral routes for our patients. We provide an overview of our "standard operation procedures" regarding candidacy, and discuss some of the special considerations that need to be applied to children with ANSD. This includes decisions to implant children with better audiometric thresholds that are standard in non-ANSD patients, concerns about the possibility of spontaneous remission and the appropriate timing of implantation. Finally we review an extensive published literature in outcomes after cochlear implantation (CI) in ANSD. This is not a systematic review but rather an exercise to distill out some important reoccurring themes and the general consensus of opinion to date. Our conclusion is that the hearing loss category ANSD, together with its numerous co-morbidities, is far too heterogeneous to make definitive statements about prognosis with CI.

Transplantation of neurons derived from human iPS cells cultured on collagen matrix into guinea-pig cochleae

The present study examined the efficacy of a neural induction method for human induced pluripotent stem (iPS) cells to eliminate undifferentiated cells and to determine the feasibility of transplanting neurally induced cells into guinea-pig cochleae for replacement of spiral ganglion neurons (SGNs). A stepwise method for differentiation of human iPS cells into neurons was used. First, a neural induction method was established on Matrigel-coated plates; characteristics of cell populations at each differentiation step were assessed. Second, neural stem cells were differentiated into neurons on a three-dimensional (3D) collagen matrix, using the same protocol of culture on Matrigel-coated plates; neuron subtypes in differentiated cells on a 3D collagen matrix were examined. Then, human iPS cell-derived neurons cultured on a 3D collagen matrix were transplanted into intact guinea-pig cochleae, followed by histological analysis. In vitro analyses revealed successful induction of neural stem cells from human iPS cells, with no retention of undifferentiated cells expressing OCT3/4. After the neural differentiation of neural stem cells, approximately 70% of cells expressed a neuronal marker, 90% of which were positive for vesicular glutamate transporter 1 (VGLUT1). The expression pattern of neuron subtypes in differentiated cells on a 3D collagen matrix was identical to that of the differentiated cells on Matrigel-coated plates. In addition, the survival of transplant-derived neurons was achieved when inflammatory responses were appropriately controlled. Our preparation method for human iPS cell-derived neurons efficiently eliminated undifferentiated cells and contributed to the settlement of transplant-derived neurons expressing VGLUT1 in guinea-pig cochleae. Copyright © 2015 John Wiley & Sons, Ltd.

Cochlear implantation in children with single-sided deafness: does aetiology and duration of deafness matter?

For adult patients with single-sided deafness (SSD), treatment with a cochlear implant (CI) is well established as an acceptable and beneficial hearing rehabilitation method administered routinely in clinical practice. In contrast, for children with SSD, CI has been applied less often to date, with the rationale to decide either on a case-by-case basis or under the realm of clinical research. The aim of our clinical study was to evaluate the longitudinal benefits of CI for a group of children diagnosed with SSD and to compare their outcomes with respect to patient characteristics. Evaluating a pool of paediatric SSD patients presenting for possible CI surgery revealed that the primary aetiology of deafness was congenital cochlear nerve deficiency. A subgroup of children meeting the CI candidacy criteria for the affected ear (the majority with acquired hearing loss) were enrolled in the study. Preliminary group results suggest substantial improvements in speech comprehension in noise and in the ability to localise sound, which was demonstrated through objective and subjective assessments after CI treatment for the group, with results varying from patient to patient. Our study shows a trend towards superior outcomes for children with acquired hearing loss and a shorter duration of hearing loss compared to congenitally deafened children who had a longer duration of SSD. This indicates an interactive influence of the age at onset, aetiology and duration of deafness upon the restoration of binaural integration and the overall benefits of sound stimulation to two ears after CI treatment. Continued longitudinal investigation of these children and further studies in larger groups may provide more guidance on the optimal timing of treatment for paediatric patients with acquired and congenital SSD.

Mutations in apoptosis-inducing factor cause X-linked recessive auditory neuropathy spectrum disorder

Background

Auditory neuropathy spectrum disorder (ANSD) is a form of hearing loss in which auditory signal transmission from the inner ear to the auditory nerve and brain stem is distorted, giving rise to speech perception difficulties beyond that expected for the observed degree of hearing loss. For many cases of ANSD, the underlying molecular pathology and the site of lesion remain unclear. The X-linked form of the condition, AUNX1, has been mapped to Xq23-q27.3, although the causative gene has yet to be identified.

Methods

We performed whole-exome sequencing on DNA samples from the AUNX1 family and another small phenotypically similar but unrelated ANSD family.

Results

We identified two missense mutations in AIFM1 in these families: c.1352G>A (p.R451Q) in the AUNX1 family and c.1030C>T (p.L344F) in the second ANSD family. Mutation screening in a large cohort of 3 additional unrelated families and 93 sporadic cases with ANSD identified 9 more missense mutations in AIFM1. Bioinformatics analysis and expression studies support this gene as being causative of ANSD.

Conclusions

Variants in AIFM1 gene are a common cause of familial and sporadic ANSD and provide insight into the expanded spectrum of AIFM1-associated diseases. The finding of cochlear nerve hypoplasia in some patients was AIFM1-related ANSD implies that MRI may be of value in localising the site of lesion and suggests that cochlea implantation in these patients may have limited success.

Auditory brainstem implant candidacy in the United States in children 0-17 years old

OBJECTIVES

The auditory brainstem implant (ABI) is an option for hearing rehabilitation in profoundly deaf patients ineligible for cochlear implantation. Over the past decade, surgeons have begun implanting ABIs in pediatric patients who are unable to receive cochlear implants due to congenital or acquired malformations of the inner ear. No study has examined the potential population-level demand for ABIs in the United States (US). Herein, we aim to quantify the potential need for pediatric ABIs.

METHODS

A systematic literature review was conducted to identify studies detailing the rates of congenital cochlear and/or cochlear nerve (CN) anomalies. Absolute indications for ABI include bilateral cochlea or CN aplasia (Group A), and relative indications for ABI include bilateral cochlea or CN hypoplasia (Group B). Data was subsequently correlated to the US Census Bureau, the National Health Interview Survey, and the Gallaudet Research Institute to provide an estimation of pediatric ABI candidates.

RESULTS

Eleven studies documented rates of bilateral findings. Bilateral cochlea aplasia was identified in 0-8.7% of patients and bilateral CN aplasia in 0-4.8% of patients (Group A). Bilateral cochlea hypoplasia was identified in 0-8.7% of patients and bilateral CN hypoplasia in 0-5.4% of patients (Group B). Using population-level sensorineural hearing loss data, we roughly estimate 2.1% of potential implant candidates meet absolute indications for an ABI in the United States.

CONCLUSION

Congenital cochlear and cochlear nerve anomalies are exceedingly rare. This study provides the first preliminary estimate of cochlea and CN aplasia/hypoplasia at the population level albeit with limitations based on available data. These data suggest the need for dedicated ABI centers to focus expertise and management.

Evaluation of internal auditory canal structures in tinnitus of unknown origin

Objectives

The aim of the present study was to evaluate the internal auditory canal (IAC) and the nerves inside it to define possible structural differences in cases with subjective tinnitus of unknown origin.

Methods

Cases applying to the ear, nose and throat department with the complaint of tinnitus with unknown origin and having normal physical examination and test results were included in the study (n=78). Patients admitted to the radiology clinic for routine cranial magnetic resonance imaging (MRI) and whose MRI findings revealed no pathologies were enrolled as the control group (n=79). Data for the control group were obtained from the radiology department and informed consent was obtained from all the patients. Diameters of the IAC and the nerves inside it were measured through enhanced images obtained by routine temporal bone MRIs in all cases. Statistical evaluations were performed using Student t-test and statistical significance was defined as P<0.05.

Results

Measurements of IAC diameters revealed statistically significant differences between the controls and the tinnitus group (P<0.05). Regarding the diameters of the cochlear nerve, facial nerve, inferior vestibular nerve, superior vestibular nerve, and total vestibular nerve, no statistically significant difference was found between the controls and the tinnitus group.

Conclusion

Narrowed IAC has to be assessed as an etiological factor in cases with subjective tinnitus of unknown origin.

Cochlear implant-evoked cortical activation in children with cochlear nerve deficiency

OBJECTIVE

To report the results of cochlear implant-elicited cortical auditory evoked potentials (eCAEP) in children with cochlear nerve deficiency (CND).

STUDY DESIGN

Case control series.

SETTING

Tertiary academic referral center.

PATIENTS

Seven children with CND that have a cochlear implant in their affected ear. Four children without CND served as controls.

INTERVENTION(S)

eCAEPs were elicited by activation of individual cochlear implant electrodes.

MAIN OUTCOME MEASURE(S)

Onset responses (P1-N1-P2 complex).

RESULTS

Three of 7 CND children demonstrated eCAEP responses across a broad range of electrodes despite having limited or no open set speech perception abilities using their implants. Two of these children had eCAEPs that were characterized by substantial variability in latency, amplitude, and number of electrodes with identifiable responses. The remaining 4 ears with CND and poor speech perception had multiphasic responses that are inconsistent with eCAEPs. Non-CND ears with excellent speech perception abilities demonstrated robust responses on all electrodes stimulated.

CONCLUSION

Abent eCAEP responses were indicative of poor open-set speech perception skills in all cases. However, eCAEP onset responses were measurable in some children with imaging evidence of CND, indicating probable cochlear nerve hypoplasia rather than aplasia. That some children with CND and poor speech perception had robust eCAEPs in some instances makes this particular measure of limited use for predicting good speech perception outcomes after cochlear implantation in these children. The origin of multiphasic responses remains to be determined but may be of somatosensory origin in some instances.

Unilateral cochlear nerve hypoplasia in children with mild to moderate hearing loss

CONCLUSION

Even if hearing loss is mild to moderate, the presence of cochlear nerve (CN) hypoplasia associated with retrocochlear disorders should be considered.

OBJECTIVES

CN hypoplasia is a term that refers to an absent cochlear nerve on high-resolution magnetic resonance imaging (MRI). Most cases of CN hypoplasia are associated with profound hearing loss. The present study reports six pediatric cases of unilateral CN hypoplasia with mild to moderate hearing loss.

METHODS

Between May 2008 and April 2011, pure-tone hearing tests were performed in 17 patients who were diagnosed with CN hypoplasia on high resolution for evaluation of unilateral sensorineural hearing loss at the National Center for Child Health and Development. Of these, six patients had average hearing levels in the affected ears of < 60 dB and were therefore included in this study.

RESULTS

All six ears with CN hypoplasia were associated with CN canal stenosis. DPOAEs were present in one (17%) of the six affected ears. The ABR thresholds of the ears with CN hypoplasia were significantly elevated compared with 1-4 kHz pure-tone hearing levels in one of three cases. In two of five cases, the maximum word recognition scores of the affected ears were poor compared with pure-tone hearing levels.

Normative diameters and effects of aging on the cochlear and facial nerves in normal-hearing Korean ears using 3.0-tesla magnetic resonance imaging

OBJECTIVES/HYPOTHESIS

To assess the normative size of the cochlear nerve (CN) and facial nerve (FN) in normal-hearing ears and to determine whether nerve size varies with age.

STUDY DESIGN

Cross-sectional.

METHODS

We included 169 ears with normal hearing between 2005 and 2010. The height, width, and cross-sectional area (CSA) of the CN and FN in the middle of the internal auditory canal were measured on oblique sagittal images of 3.0-T magnetic resonance imaging. Results were compared by age. Young subjects were divided into three age groups, 0-5, 6-10, and 11-15 years. Subjects over age 40 years were divided into groups at 10-year intervals.

RESULTS

Mean age was 32.6 years (range, 0.75-79 years). We found that the CN had significantly greater vertical (1.10 ± 0.21 mm vs. 0.95 ± 0.21 mm) and horizontal (1.11 ± 0.20 mm vs. 1.03 ± 0.22 mm) diameters than the FN. The CSA of the CN was larger than that of the FN (0.98 ± 0.33 mm(2) vs. 0.79 ± 0.31 mm(2) ). Except for the CN vertical diameter, there were no significant differences between right and left ears. Sex did not affect the nerve size. Although the CN was not affected by age, the FN vertical diameter and CSA of children <5 years were significantly smaller than those of children aged >5 years. The size of the two nerves did not differ among groups over age 40 years.

CONCLUSIONS

The CN is not affected by age in normal-hearing ears. The FN vertical diameter and CSA of children <5 years are smaller than those of older children.