Cochlear neuronal populations in developmental defects of the inner ear. Implications for cochlear implantation

Cochlear Implantation by Veria Technique in Abnormal Cochlea: Our Experience

This study describes the clinical profile, operative findings, surgical technique, type of implant and complications encountered in implantation of abnormal cochlea by the transcanal (veria) technique in a tertiary care centre. This is a retrospective study done amongst 337 patients who underwent cochlear implantation by veria technique between January 2013 to August 2023. Based on pre-operative imaging with high-resolution computed tomography and magnetic resonance imaging the cochleovestibular malformations in this study were classified according to Sennaroglu classification and the cochlear ossification was graded from I to IV. Amongst the 337 patients who underwent cochlear implantation during the study period there were 79 cases (23.4%) with abnormalities of cochlea. This included 45 patients (13.4%) with congenital malformations, 20 patients (5.9%) with cochlear fibrosis and 14 patients (4.2%) with cochlear ossification. The commonest cochlear malformation was Incomplete Partition 2 which was present in 21 patients (46.7%). The other common malformations were cochlear hypoplasia (31.1%), Incomplete Partition 1(13.3%) and common cavity (8.9%). Out of the 20 patients with cochlear fibrosis, 17 patients had fibrosis only in the basal turn. Out of the 14 patients with cochlear ossification 8 patients (57.1%) had a grade 1 ossification, 2 patients (14.3%) had a grade 2 ossification and 4 patients (28.6%) had a grade 3 ossification. One of the patients required re-exploration for correcting the placement of electrode. The type of implant were chosen depending on individual malformation or length of ossification and fibrosis. In the past, inner ear anomalies were considered as a contraindication for cochlear implantation however it is now possible to implant most of these abnormal cochlea by careful planning, a modification of the surgical technique and the type of electrode used.

The effect of cochlear size on electrically evoked auditory brainstem responses in deaf children

Objectives

To investigate the relationship between auditory pathway function and cochlear size in deaf children with a radiologically normal inner ear or Mondini malformation.

Methods

Thirty-five deaf children without inner ear malformations (IEMs) and forty cases with Mondini malformation were included in this study. The electrically evoked auditory brainstem responses (EABRs) evoked by electrical stimulation at the round window niche (RWN) and round window membrane (RWM) were recorded during cochlear implantation (CI) surgery. The anatomical parameters of the cochlea were assessed by high-resolution computed tomography and OTOPLAN 3-D construction software. Correlations between EABRs and cochlear sizes were analyzed.

Results

The EABR thresholds and/or latencies were negatively correlated with the basal cochlear diameter, cochlear width and/or cochlear duct length in both patients without IEMs and those with Mondini malformation.

Conclusion

The physiological function of the peripheral auditory system depends on the anatomical structure of the cochlea to an extent. A larger cochlear size appears to be associated with better auditory conduction function. Our findings may be beneficial to selection of the proper electrode type and prediction of postoperative auditory rehabilitation.

Level of Evidence

Level 4.

Cochlear implantation in children with congenital inner ear malformations - Our experience

OBJECTIVE

To share our experience of the surgical challenges faced in cochlear implanted patients with inner ear malformation and to assess the auditory and speech perception outcomes.

MATERIAL AND METHOD

Clinical records of 502 cochlear implant procedures were reviewed and data of 122 patients who had inner ear malformations were enrolled in the study. Their auditory and speech performances were evaluated post implantation for 3 years.

RESULT

Cerebrospinal fluid gusher was encountered during opening of cochlea in 42 patients (34.4%) and one patient was re-explored within 24 h. In 30.3% of cases facial anomaly was found. Significant improvement in average performance was seen in all malformation types except in cochlear hypoplasia at 12 months postoperatively.

CONCLUSION

Surgical challenges can be overcome with expertise and giving special attention to preoperative imaging. Our experience suggests that outcomes are favourable in patients with inner ear malformations too.

Cochlear base length as predictor for angular insertion depth in incomplete partition type 2 malformations

INTRODUCTION

The preoperative determination of suitable electrode array lengths for cochlear implantation in inner ear malformations is a matter of debate. The choice is usually based on individual experience and the use of intraoperative probe electrodes. The purpose of this case series was to evaluate the applicability and precision of an angular insertion depth (AID) prediction method, based on a single measurement of the cochlear base length (CBL).

METHODS

We retrospectively measured the CBL in preoperative computed tomography (CT) images in 10 ears (8 patients) with incomplete partition type 2 malformation. With the known electrode length (linear insertion depth, LID) the AID at full insertion was retrospectively predicted for each ear with a heuristic equation derived from non-malformed cochleae. Using the intra- or post-implantation cone beam CT images, the actual AID was assessed and compared. The deviations of the predicted from the actual insertion angles were quantified (clinical prediction error) to assess the precision of this single-measure estimation.

RESULTS

Electrode arrays with 15 mm (n = 3), 19 mm (n = 2), 24 mm (n = 3), and 26 mm (n = 2) length were implanted. Postoperative AIDs ranged from 211° to 625°. Clinical AID prediction errors from -64° to 62° were observed with a mean of 0° (SD of 44°). In two ears with partial insertion of the electrode, the predicted AID was overestimated. The probe electrode was intraoperatively used in 9/10 cases.

CONCLUSION

The analyzed method provides good predictions of the AID based on LID and CBL. It does not account for incomplete insertions, which lead to an overestimation of the AID. The probe electrode is useful and well established in clinical practice. The investigated method could be used for patient-specific electrode length selection in future patients.

Pediatric cochlear implant fitting parameters in inner ear malformation: Is it same with normal cochlea?

OBJECTIVES

The aim was to evaluate the cochlear implant (CI) mapping parameters of CI users with inner ear malformation (IEM) and to reveal the changes in parameters over time.

METHODS

In total, 118 CI users were included with 127 ears (68-IEM; 59-normal cochlear anatomy) in present retrospective study. The impedance measurements, thresholds levels-THR, most comfortable levels- MCL, pulse width-PW and rate values were analyzed in both IEM and control group at the initial activation, 6th,12th and 24th months postoperatively.

RESULTS

There were statistically significant differences in impedance measurements in several time points. And also, there was a remarkable difference in THR & MCL and PW values between IEM and control groups in all time points (p < 0.05). THR & MCL levels and PW values increased significantly between all time periods in both groups (p < 0,008) and values of parameters in IEM-group were higher than those of control group. When comparing rates, statistically significant difference was observed only at the initial activation in both within (p < 0.001) and between groups (p = 0.03).

CONCLUSION

Pediatric CI users with IEM need individual changes in fitting parameters. More frequent map sessions should be planned as they require more PW, THR and MCL increase over time. The increase rate differs between IEM subgroups depending on the deviation of malformation from the normal cochlear anatomy. This study is the first to in its attempt to reveal the mapping characteristics and long-term changes in pediatric CI users with different IEM subgroups.

Potential Implications of Slim Modiolar Electrodes for Severely Malformed Cochleae: A Comparison With the Straight Array With Circumferential Electrodes

Objectives

Malformations of the inner ear account for approximately 20% of cases of congenital deafness. In current practice, straight arrays with circumferential electrodes (i.e., full-banded electrodes) are widely used in severely malformed cochleae. However, the unpredictability of the location of residual spiral ganglion neurons in such malformations argues against obligatorily using full-banded electrodes in all cases. Here, we present our experience of electrically evoked compound action potential (ECAP) and radiography-based selection of an appropriate electrode for severely malformed cochleae.

Methods

Three patients with severely malformed cochleae, showing cochlear hypoplasia type II (CH-II), incomplete partition type I (IP-I), and cochlear aplasia with a dilated vestibule (CADV), respectively, were included, and the cochlear nerve deficiency (CND) was evaluated. A full-banded electrode (CI24RE(ST)) and slim modiolar electrode (CI632) were alternately inserted to compare ECAP responses and electrode position.

Results

In patient 1 (CH-II with CND), who had initially undergone cochlear implantation (CI) using a lateral wall electrode (CI422), revision CI was performed due to incomplete insertion of CI422 and resultant unsatisfactory performance by explanting the CI422 and re-inserting the CI24RE(ST) and CI632 sequentially. Although both electrodes elicited reliable ECAP responses with correct positioning, CI24RE(ST) showed overall lower ECAP thresholds compared to CI632; thus, CI24RE(ST) was selected. In patient 2 (IP-I with CND), CI632 elicited superior ECAP responses relative to CI24RE(ST), with correct positioning of the electrode; CI632 was chosen. In patient 3 (CADV), CI632 did not elicit an ECAP response, while meaningful ECAP responses were obtained with the CI24RE(ST) array once correct positioning was achieved. All patients’ auditory performance markedly improved postoperatively.

Conclusion

The ECAP and radiography-based strategy to identify an appropriate electrode may be useful for severely malformed cochleae, leading to enhanced functional outcomes. The practice of sticking to full-banded straight electrodes may not always be optimal for IP-I and CH-II.

Cochlear implantation in common cavity deformity: a systematic review

PURPOSE

Cochlear implantation became a valid hearing rehabilitation option in common cavity deformity. This study aimed to assess the audiological and speech outcomes of cochlear implantation in common cavity deformity patients and to address the surgical aspect used in this population.

METHODS

A comprehensive systematic literature review based on preferred reporting items for systematic reviews and meta-analyses (PRISMA) guideline from database inception through April 2020. Eighteen published articles including 138 patients with common cavity deformity met the inclusion criteria. These articles studied the surgical techniques and the audiological outcomes of cochlear implantation in patients with common cavity deformity in English language.

RESULTS

Trans-mastoid labyrinthotomy was the common surgical approach in these patients. The average speech intelligibility rating and categories of auditory performance scores in common cavity deformity were lower than in normal cochlea subjects (p < 0.05), and non-significant (p > 0.05) compared with other types of inner ear malformations.

CONCLUSION

Patients with common cavity deformity who underwent cochlear implantation showed a beneficial audiological and speech outcome. However, their performance is highly variable. Therefore, pre-operative counseling of the parents is necessary. The surgical approaches should be individualized according to clinical, radiological, and surgical findings.

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.

Cochlear implantation in children with Mondini dysplasia: our experience

OBJECTIVE

This study details the intra-operative complications, and compares auditory scales post-implantation of either profoundly deaf young children with radiologically normal inner ears (group A) or children with Mondini dysplasia (group B).

METHODS

A retrospective survey was carried out of 338 patients with severe to profound sensorineural hearing loss who underwent cochlear implant surgery from February 2015 to May 2017. Patients were divided into 2 groups of 27 patients each. Both groups were followed up to three years post-implantation.

RESULTS

Cerebrospinal fluid ooze developed in 12 patients, and 2 patients had a cerebrospinal fluid 'gusher', one of which had to be explored within 24 hours. After implant use for one year, both groups had similar speech perception scores.

CONCLUSION

The cerebrospinal fluid gusher in Mondini dysplasia should be anticipated and adequately managed intra-operatively. This study highlights the tailoring of a post-implantation rehabilitation programme according to individual needs.

Literature Review on the Distribution of Spiral Ganglion Cell Bodies inside the Human Cochlear Central Modiolar Trunk

This study aims to obtain a better understanding of the number and distribution of spiral ganglion cell bodies (SGCBs) in the central modiolar trunk of the human cochlea with normal hearing as well as with hearing loss due to various pathological conditions. A detailed PubMed search was performed using the key words "human spiral ganglion cell population," "analysis of spiral ganglion cell population," "survival of human spiral ganglion cells," "human Rosenthal's canal," "human ganglion cell counts," and "distribution of human spiral ganglion cells" to identify articles published between 1931 and 2019. The articles were included if the number of SGCBs in the four segments of the human cochlea and angular depth distribution of the SGCBs were mentioned. Out of the 237 articles that were initially identified, 20 articles met the inclusion criteria. The presence of SGCBs inside the Rosenthal's canal (RC) in the modiolar trunk extended to an angular depth of 630°-680°, which is close to the end of the second turn of the cochlea. SGCBs in Segment-IV of the cochlea account for approximately 25-30% of the entire SGCB population, regardless of the cochlear condition (normal vs. pathologic). In normal-hearing subjects, the total number of SGCB cases ranged between 23,910 and 33,702; in patients with hearing loss, the same was between 5,733 and 28,220. This literature review elaborates on the current state of knowledge regarding the number and distribution of SGCBs in the human cochlea.

A Ten-Year Review of Audiological Performance in Children with Inner Ear Abnormalities after Cochlear Implantation in Singapore

OBJECTIVES

To evaluate children with inner ear malformations following cochlear implantation (CI) in a tertiary pediatric hospital in Singapore to identify factors influencing outcomes after CI.

METHODS

This is a retrospective cohort study of children aged 0 to 18 years, who had CI between 2000 and 2013. Demographic information, data on risk factors, type of inner ear malformation (IEM), age at implantation, speech pre- and postimplantation, and duration of follow-up were collected from clinical records. Operative details and audiological outcomes were also analyzed.

RESULTS

A total of 70 children underwent 83 CI surgeries. The mean age of the patients was 4.05 ± 3.17 years (range 1-18 years). Twenty patients (28.57%) had abnormal CT scan findings. CSF gusher occurred in 15 out of 26 CI (57.69%) in the group with IEM. Nine out of twenty patients (45.00%) had poor IT-MAIS scores prior to implantation. The average preoperative IT-MAIS score for children with anomalous inner ear anatomy was 14.1. The older CI patients, 3/20 (15.00%), mean age 8.33 years (range 7-10 years), were mostly referred for persistently unclear speech following hearing aids. Eleven patients (55.00%) had good speech and aided hearing threshold within speech limits after CI and were eligible for reintegration into mainstream schools. Five patients (25.00%) had improvement in speech but continued to receive education in special schools. Four patients (20.00%) had poor progress after surgery.

CONCLUSION

The presence of absent cochlear nerve, electrode folding, and underlying neurological disorders seemed to be associated with poorer outcomes.

Presence of the spiral ganglion cell bodies beyond the basal turn of the human cochlea

The purpose of this study was to obtain a better understanding of the number and distribution of spiral ganglion cell bodies (SGCB) in the central modiolus trunk of the human cochlea with normal hearing as well as with hearing loss due to various pathological conditions. A literature review was performed using the key words 'human spiral ganglion cell population', 'analysis of spiral ganglion cell population', 'survival of human spiral ganglion cells', 'human Rosenthal's canal', 'human ganglion cell counts', and 'distribution of human spiral ganglion cells' to identify articles published between 1968 and 2018. Articles were included if the number of SGCB in the four segments of the human cochlea and angular depth distribution of the SGCB were stated. Of 236 articles initially identified, 19 articles met the inclusion criteria. SGCB inside the Rosenthal's canal (RC) in the modiolus trunk extended to an angular depth of 630-680° which is near the end of the second turn of the cochlea. SGCBs in Segment IV of the cochlea account for approximately 25-30% of the entire SGCB population irrespective of the cochlear condition (normal vs. pathologic). In normal hearing subjects, the total number of SGCB ranged between 23,910 and 33,702 and in patients with hearing loss between 5733 and 28,220. This literature review elaborates on the current state of knowledge about the number and distribution of SGCB in the human cochlea.

Speech development in young children with Mondini dysplasia who had undergone cochlear implantation

OBJECTIVE

The purpose of this study was to investigate the development of speech skills in young children with Mondini dysplasia and age-matched deaf children with radiologically normal inner ears over a period of 5 years after cochlear implantation (CI).

METHODS

In total, 700 congenitally severely to profoundly deaf children (281 girls and 419 boys) participated in this study. All of the participants had undergone unilateral CI surgery before 36 months of age. The participants were categorized into two groups based on the absence or presence of Mondini dysplasia in the implanted ear, as assessed via high-resolution, thin-slice computerized tomography or magnetic resonance imaging: group A comprised 592 children with radiologically normal inner ears and group B comprised 108 children with Mondini dysplasia. The Meaningful Use of Speech Scale (MUSS) and Speech Intelligibility Rating (SIR) were used to evaluate the speech performance of all young children at various time points: pre-surgery and at 1, 3, 6, 12, 24, 36, 48, and 60 months after switch-on programming.

RESULTS

The mean scores of SIR and MUSS in children from both group A and group B showed significant improvements over time. No significant differences were found in the mean scores of SIR between the two groups at any time interval during the 5-year follow-up. The mean score of MUSS was significantly different between group A and group B at 12, 24, and 36 months after implantation, whereas no obvious differences were noted pre-surgery, and at 1, 3, 6, 48, and 60 months post-operation.

CONCLUSIONS

Young children with Mondini dysplasia develop their speech skills at a fast rate and achieve similar speech acquisition compared to age-matched children with radiologically normal inner ears 5 years post-operation. Therefore, CI is an effective intervention method for young children with Mondini dysplasia.

Why Pre-Curved Modiolar Hugging Electrodes Only Cover The Basal Turn of The Cochlea and Not Beyond that?

The question of why pre-curved modiolar hugging (MH) electrodes only cover the basal turn of the cochlea and not beyond that is unanswered yet in the CI field. Therefore the aim of this article is to show what the practical limitations are with the pre-curved MH electrode design in not being able to fabricate beyond one full turn. Every CI electrode design needs a metal mold with grooves for placing the platinum wires and for injecting with the silicone elastomer. Limitations in making a mold with groove that goes beyond one full turn of curvature along with the mechanical deformation of the curved silicone elastomer, prevents making a pre-curved MH electrode beyond one full turn. Electrode tip fold-over, electrode scalar deviation and the inconsistent electrode to modiolus wall proximity are the reported issues with this electrode type which does not help by any means to the operating surgeon and the pediatric candidates especially. If intra-operative imaging is recommended to confirm the proper placement of the electrode for one particular electrode design, then how many clinics in the world may have this facility and is it ethical to put the patient under more radiation risk are the natural questions that needs to be answered in the interest of the patient. Every CI brand should come out of their marketing philosophy and innovate what is essential in bringing the full benefit of the device to the patients.

The Physiologic and Psychophysical Consequences of Severe-to-Profound Hearing Loss

Substantial loss of cochlear function is required to elevate pure-tone thresholds to the severe hearing loss range; yet, individuals with severe or profound hearing loss continue to rely on hearing for communication. Despite the impairment, sufficient information is encoded at the periphery to make acoustic hearing a viable option. However, the probability of significant cochlear and/or neural damage associated with the loss has consequences for sound perception and speech recognition. These consequences include degraded frequency selectivity, which can be assessed with tests including psychoacoustic tuning curves and broadband rippled stimuli. Because speech recognition depends on the ability to resolve frequency detail, a listener with severe hearing loss is likely to have impaired communication in both quiet and noisy environments. However, the extent of the impairment varies widely among individuals. A better understanding of the fundamental abilities of listeners with severe and profound hearing loss and the consequences of those abilities for communication can support directed treatment options in this population.

Cochlear implantation in Mondini's deformity: could the straight electrode array with length of 31 mm be fully inserted?

CONCLUSIONS

The straight electrode array with length of 31 mm can be fully inserted using round window insertion in cochlear implantation with Mondini's deformity. It is a safe and effective process, but also a challenging task of the full implantation in children with Mondini's deformity.

OBJECTIVE

The aim of this study is to discuss whether the straight electrode array with a length of 31 mm could be fully inserted in cochlear implantation with Mondini's deformity.

METHODS

A chart review of 30 patients undergoing cochlear implantation with Mondini's deformity using the electrode array with length of 31 mm was undertaken from January 2012 and December 2015 in Anhui Provincial Hospital.

RESULTS

Full insertion of the straight electrode array with length of 31 mm were performed successfully in all patients with Mondini's deformity using round window insertion. Resistance was not encountered while introducing the electrodes. Ten of 30 patients had cerebrospinal fluid drainage during cochlear implantation. Cerebrospinal fluid drainage was controlled with small pieces of temporalis fascia packing round window in all patients. Intra-operative neural response telemetry was performed in all patients, and results were good. The result of X-ray showed proper placement of the cochlear implant electrode array. During surgery, no patients had experienced any immediate or delayed post-operative complications such as wound infection, intracranial complication, extrusion, or migration of the implant during an average follow-up period of 6-36 months.

Cochlear Implantation in Children with Inner Ear Malformations

Objectives:

The aim of this study was to assess the outcomes of cochlear implantation in children with inner ear malformations (IEMs).

Methods:

A retrospective review of 212 children who received implants from September 1994 to May 2004 was performed. Forty-six of them had radiologic evidence of IEMs. The preoperative evaluations, intraoperative findings, postoperative complications, and performance outcomes were analyzed. For the comparative analysis of performance outcomes, the children with IEMs were matched and compared with children with a normal inner ear who had received implants. Statistical analysis was performed with a repeated-measures analysis of variance.

Results:

All of the children were studied with computed tomography and magnetic resonance imaging. Three-dimensional volume rendering of magnetic resonance images was performed in cases that were difficult to interpret because of structural complexity. The operative findings included aberrant facial nerves in 2 children and cerebrospinal fluid gushers in 22 children. Intraoperative fluoroscopic examination was performed to evaluate electrode placement. There were no serious postoperative complications. All children with IEMs achieved open-set speech perception abilities, except for the children with a narrow internal auditory canal (IAC), and showed progressive improvement of their speech perception abilities over time. There were no statistically significant differences in performance measured by the Common Phrases test between the 2 groups. Although the repeated-measures analysis of variance indicated that children with IEMs performed more poorly than those with a normal inner ear on the Phonetically Balanced Kindergarten test for phonemes, statistical significance was not found at 2 years after implantation. The children with a narrow IAC benefited from the implantation and used the device every day, although their speech perception abilities were limited.

Conclusions:

The results of the present study show that cochlear implantation can be performed relatively safely in deaf children with IEMs and that they receive considerable benefit from their implants. Substantial benefit can be expected from implantation in children with most kinds of IEMs, except for a narrow IAC, which is often associated with limited results.

Effectiveness of cochlear implant in inner ear bone malformations with anterior labyrinth involvement

OBJECTIVE

To study electrical stimulation, auditory functionality, and language development in patients with inner ear malformations involving the anterior labyrinth who underwent cochlear implantation.

STUDY DESIGN

Retrospective case review.

SETTING

Reference hospital for cochlear implantation.

PATIENTS

Review of 14 cases of severe hearing loss with major (common cavity deformity and cochlear hypoplasia) or minor (e.g., incomplete partition and basal turn aplasia) malformations.

INTERVENTIONS

After cochlear implantation, data were gathered on the threshold (THR) and maximum comfort level (MCL) of the electrical stimulation and the number of functioning electrodes. Auditory responses to speech (EARS protocol) subtests were used to evaluate auditory functionality and language acquisition at 6, 12, and 24 months post-implantation. Tests used were: LIP profile, MTP (3, 6 and 12 words), OLD (open set test) and CLD (close set test). Results were compared with findings in a control group of 28 cochlear implantation patients without these malformations and with congenital hearing loss.

RESULTS

The mean THR was 11.02μC in patients with malformations versus 3.5μC in those without, a significant difference. The THR also significantly differed between groups with major and minor malformations. Fewer functioning electrodes were used in patients with malformations. Auditory functionality scores were best in controls than in patients with malformations, who scored ≤50%, finding the lowest scores in those with major malformations.

CONCLUSION

Patients with inner ear malformations undergoing cochlear implantation require greater stimuli to obtain an auditory response and have worse auditory functionality outcomes; these differences are greater in those with major versus minor malformations Nevertheless, cochlear implantation appears to be beneficial for all patients with these malformations to a greater or lesser extent.

The development of auditory skills in young children with Mondini dysplasia after cochlear implantation

The aim of this study is to survey and compare the development of auditory skills in young children with Mondini dysplasia and profoundly-deaf young children with radiologically normal inner ears over a period of 3 years after cochlear implantation. A total of 545 young children (age 7 to 36 months) with prelingual, severe to profound hearing loss participated in this study. All children received cochlear implantation. Based on whether or not there was a Mondini dysplasia as diagnosed with CT scanning, the subjects were divided into 2 groups: (A) 514 young children with radiologically normal inner ears and (B) 31 young children with Mondini dysplasia. The Infant-Toddler Meaningful Auditory Integration Scale (IT-MAIS) was used to assess the children's auditory skills that include vocalization changes, spontaneous alerting to sounds in everyday living environments, and the ability to derive meaning from sounds. The assessment was performed prior to surgery and at 1, 3, 6, 9, 12, 24, and 36 months after implant device switch-on. The mean scores for overall auditory skills were not significantly different between groups A and B at pre-surgery, 1, 12, 24, and 36 months post-surgery, but were significantly different at 3, 6, and 9 months post-surgery. The mean scores for all auditory skills in children with Mondini dysplasia showed significant improvement over time. The mean scores for the three subcategories of auditory skills in children with Mondini dysplasia also showed significant differences at pre-surgery, 1, 3, 6, and 9 months, however, there were no significant differences at 12, 24, and 36 months. Overall, the auditory skills of young children with Mondini dysplasia developed rapidly after cochlear implantation, in a similar manner to that of young children with radiologically normal inner ears. Cochlear implantation is an effective intervention for young children with Mondini dysplasia.

Pediatric cochlear implantation: an update

Deafness in pediatric age can adversely impact language acquisition as well as educational and social-emotional development. Once diagnosed, hearing loss should be rehabilitated early; the goal is to provide the child with maximum access to the acoustic features of speech within a listening range that is safe and comfortable. In presence of severe to profound deafness, benefit from auditory amplification cannot be enough to allow a proper language development. Cochlear implants are partially implantable electronic devices designed to provide profoundly deafened patients with hearing sensitivity within the speech range. Since their introduction more than 30 years ago, cochlear implants have improved their performance to the extent that are now considered to be standard of care in the treatment of children with severe to profound deafness. Over the years patient candidacy has been expanded and the criteria for implantation continue to evolve within the paediatric population. The minimum age for implantation has progressively reduced; it has been recognized that implantation at a very early age (12-18 months) provides children with the best outcomes, taking advantage of sensitive periods of auditory development. Bilateral implantation offers a better sound localization, as well as a superior ability to understand speech in noisy environments than unilateral cochlear implant. Deafened children with special clinical situations, including inner ear malformation, cochlear nerve deficiency, cochlear ossification, and additional disabilities can be successfully treated, even thogh they require an individualized candidacy evaluation and a complex post-implantation rehabilitation. Benefits from cochlear implantation include not only better abilities to hear and to develop speech and language skills, but also improved academic attainment, improved quality of life, and better employment status. Cochlear implants permit deaf people to hear, but they have a long way to go before their performance being comparable to that of the intact human ear; researchers are looking for more sophisticated speech processing strategies as well as a more efficient coupling between the electrodes and the cochlear nerve with the goal of dramatically improving the quality of sound of the next generation of implants.

Hearing level in children with Down syndrome at the age of eight

This study examines the prevalence of hearing loss in children with Down syndrome at the age of 8. All children were examined in the ENT-departments of public hospitals in Norway and the study population consisted of children born in Norway in 2002 with Down syndrome. Hearing loss was defined as pure-tone air-conduction reduction by on average more than 25 dB HL in the best hearing ear. A cross sectional clinical and audiological population based study was chosen as study design. Hearing loss more than 25 dB HL in the best hearing ear was found in 17/49 children (35%). Mild hearing loss was found in 13 children (26%), moderate in 3 (6%) children and severe hearing loss in 1 child (2%). Conductive hearing loss was found in 8 children (16%), 9 children (18%) had a sensory-neural hearing loss, and mixed hearing loss was found in 3 children. Mean hearing level among boys and girls were 30.0 dB HL (SD 15.7) and 25.5 dB HL (SD13.7) respectively, a non-significant difference (p=0.139). In conclusion this study indicates that both conductive and sensorineural hearing loss, is still common in children with Down syndrome children at the age of eight and as much as two thirds of the children may have a bilateral impairment. The study population was under diagnosed in terms of hearing loss and thus our findings underline the importance of continuous audiological follow up of this group of children throughout childhood.

Speech perception and production in children with inner ear malformations after cochlear implantation

OBJECTIVE

The aim of this study was to assess the speech perception and speech intelligibility outcome after cochlear implantation in children with malformed inner ear and to compare them with a group of congenitally deaf children implantees without inner ear malformation.

METHODS

Six deaf children (five boys and one girl) with inner ear malformations who were implanted and followed in our clinic were included. These children were matched with six implanted children with normal cochlea for age at implantation and duration of cochlear implant use. All subjects were tested with the internationally used battery tests of listening progress profile (LiP), capacity of auditory performance (CAP), and speech intelligibility rating (SIR). A closed and open set word perception test adapted to the Modern Greek language was also used. In the dysplastic group, two children suffered from CHARGE syndrome, another two from mental retardation, and two children grew up in bilingual homes.

RESULTS

At least two years after switch-on, the dysplastic group scored mean LiP 62%, CAP 3.8, SIR 2.1, closed-set 61%, and open-set 49%. The children without inner ear dysplasia achieved significantly better scores, except for CAP which this difference was marginally statistically significant (p=0.009 for LiP, p=0.080 for CAP, p=0.041 for SIR, p=0.011 for closed-set, and p=0.006 for open-set tests).

CONCLUSION

All of the implanted children with malformed inner ear showed benefit of auditory perception and speech production. However, the children with inner ear malformation performed less well compared with the children without inner ear dysplasia. This was possibly due to the high proportion of disabilities detected in the dysplastic group, such as CHARGE syndrome and mental retardation. Bilingualism could also be considered as a factor which possibly affects the outcome of implanted children. Therefore, children with malformed inner ear should be preoperatively evaluated for cognitive and developmental delay. In this case, counseling for the parents is mandatory in order to explain the possible impact of the diagnosed disabilities on performance and habilitation.

Hearing improvement after cochlear implantation in common cavity malformed cochleae: long-term follow-up results

CONCLUSION

We suggest that cochlear implantation (CI) should be a good therapeutic modality for hearing restoration in patients with common cavity malformed ears.

OBJECTIVE

To analyze hearing improvement from CI performed in common cavity malformed cochleae.

METHODS

A total of 11 patients (5 male and 6 female, mean age 4.5 ± 2.8 years) and 12 ears were enrolled in this study. During the insertion of electrodes, we used C-arm fluoroscopy to avoid intrameatal placement. We evaluated hearing improvement every 6 months and the mean follow-up period was 80.5 ± 24.1 months (53-125 months).

RESULTS

During the operation, there were only four cases with fully inserted electrodes. Cerebrospinal fluid gushed out in two cases during the cochleostomy and postoperative meningitis occurred in two patients. One patient had to undergo reimplantation 4 years later due to device failure and recurrent meningitis. During the 48 months follow-up hearing evaluation, the ability of hearing increased along with the age. The final average MAIS, CAP, SIR, and open set one- and two-syllable word scores were 90.3 ± 18.1%, 4.9 ± 1.6, 3.1 ± 0.9, 24.1 ± 25.9%, and 48.6 ± 38.7%, respectively.

Speech in Individuals With Down Syndrome

This article reviews the development of articulation and phonology in young children with Down syndrome. After summarizing factors that impact the development of speech, the authors review assessment and intervention of speech sound disorders in this population.

Cochlear neuronal tracing for frequency mapping with DiI, NeuroVue, and Golgi methods

CONCLUSIONS

Labeling experiments using NeuroVue Red dye allowed us to demonstrate individual afferent fiber tracks in the cochlea from the synaptic region of the inner hair cell in the organ of Corti (OC) to the spiral ganglion in Rosenthal's canal. Further optimization is necessary to obtain 3-dimensional (3D) neural distribution in the apical region for frequency mapping.

OBJECTIVES

We intend to develop a method by which the radial fibers of the spiral ganglion (SG) can be individually visualized and tracked in 3D from the base to the apex of the cochlea. The combined trajectories of fibers from each cochlea could then be calculated for modeling of the 3D relationship of OC and SG in cochlear implant studies to assist in the optimization of cochlear implants for music and speech perception in noise.

MATERIALS AND METHODS

We tested three different methods to visualize cochlear nerve fibers from OC to SG. Adult rat and mouse ears were stained with DiI dye, modified Golgi-Cox method or NeuroVue dye, sectioned or whole-mounted, and viewed with confocal or standard light microscope.

RESULTS

In DiI staining, spacial resolution and the number of neurons to be stained are too low to utilize this method to create a characteristic frequency map of the cochlea. The Golgi method mainly stained efferent nerve fibers, resulting in less information on cochlear nerve distribution. NeuroVue Red dye allowed clear tracking of individual fibers when combined with DAPI counterstaining.

Effects of auditory pathway anatomy and deafness characteristics? Part 2: On electrically evoked late auditory responses

The purpose of this study was to distinguish the effects of different parameters on latencies of wave N1, wave P2, and inter-peak interval N1-P2 of electrical late auditory responses (ELARs). ELARs were recorded from four intra-cochlear electrodes in fourteen adult HiRes90K cochlear implant users who had at least three months of experience. The relationship between latencies and stimulation sites in the cochlea was characterized to assess the influence of the auditory pathway anatomy on ELARs, i.e., whether the speed of neural propagation varies according to the place that is activated in the cochlea. Audiograms before implantation, duration of deafness, and psychophysics at first fitting were used to describe the influence of deafness characteristics on latencies. The stimulation sites were found to have no effect on ELAR latency and, while there was no influence of psychophysics on latency, a strong relationship was shown with duration of deafness and the pre-implantation audiogram. Thus, ELAR latency was longer for poorer audiograms and longer durations of deafness and this relationship appeared to be independent of stimulation parameters such as stimulation site. Comparison between these findings and those from the equivalent study on EABR waves IIIe and Ve latency [Guiraud, J., Gallego, S., Arnold, L., Boyle, P., Truy, E., Collet, L., 2007. Effects of auditory pathway anatomy and deafness characteristics? (1): On electrically evoked auditory brainstem responses. Hear. Res. 223 (1-2), 48-60] shows that, while ELAR and EABR latencies are related with parameters that reflect the integrity of the auditory pathway, ELAR latency is less dependent on stimulation parameters than EABR latency.

Effects of auditory pathway anatomy and deafness characteristics? (1): On electrically evoked auditory brainstem responses

The purpose of this study was to distinguish the effects of different parameters on latencies of wave IIIe, wave Ve, and interpeak interval IIIe-Ve of electrical auditory brainstem responses (EABRs). EABRs were recorded from all the intra-cochlear electrodes in eight adult HiRes90K((R)) cochlear implant users. The relationship between latencies and stimulation sites in the cochlea was characterized to assess activity along the auditory pathway. Audiograms before implantation, psychophysics at first fitting and duration of deafness were used to describe the influence of deafness on latencies. A decreasing baso-apical latency gradient was found for waves IIIe and Ve, while the interpeak interval IIIe-Ve remained the same along the electrode array. Electrical stimulation enabling to stimulate various parts of the cochlea at the same time, this could indicate an anatomical way of compensating for the delay the acoustic wave takes to reach the cochlea apex in a non-implanted ear. However, psychophysical levels were also found to increase at the cochlear base showing that the latency gradient could result from an increasing gradient of neural degeneration toward the base. Correlations of EABR latencies with psychophysics, audiometric data and duration of deafness show that factors linked to deafness have indeed an influence on EABR latencies. The possible explanations for the latency shift observed, whether they are anatomical and/or pathological, are exposed.

Inner Ear Dysplasia is Common in Children With Down Syndrome (trisomy 21)

OBJECTIVES/HYPOTHESIS

Middle and external ear anomalies are well recognized in Down syndrome (DS, trisomy 21). Inner ear anomalies are much less frequently described. This study reviews inner ear morphology on imaging to determine the prevalence of cochlear and vestibular anomalies in children with DS.

STUDY DESIGN

The authors conducted a retrospective review of imaging features of (DS) inner ear structures.

METHODS

Fifty-nine sequential patients with DS with imaging of the inner ear were identified by a radiology report text search program. Quantitative biometric assessment of the inner ear was performed on patients with high-resolution computed tomography or magnetic resonance images of the petrous bone. Petrous imaging was performed for evaluation of inflammatory disease or hearing loss. Spinal imaging, which included petrous views, was performed in most cases to exclude C1 to 2 dislocation, a potential complication of DS. Measurements were compared with normative data.

RESULTS

Inner ear dysplasia is much more common in DS than previously reported. Inner ear structures are universally hypoplastic. Vestibular malformations are particularly common and a small bony island of the lateral semicircular canal (<3 mm in diameter) appears highly typical. Additional findings in some patients were persistent lateral semicircular anlage with fusion of the lateral semicircular canal and vestibule into a single cavity, vestibular aqueduct and endolymphatic sac fossa enlargement, cochlear nerve canal hypoplasia, and stenosis or duplication of the internal auditory canal. Stenosis of the external meatus, poor mastoid pneumatization, middle ear and mastoid opacification, and cholesteatoma were common, as expected.

Surgical Results of Cochlear Implantation in Malformed Cochlea

OBJECTIVE

To report the surgical aspects of cochlear implantation in malformed cochlea.

SETTING

Tertiary care center.

STUDY DESIGN

Retrospective case review.

METHODS

Between November 1997 and October 2004, 20 patients with inner ear malformations were implanted in our department. The age range was between 2 and 37 years (average, 8.8 yr). The anomalies were classified according to Sennaroglu and Saatci classification. There were two patients with common cavity deformity, four cases of incomplete partition (IP) type I (cystic cochleovestibular malformation), four cases of IP type II (classical Mondini's deformity), nine patients with large vestibular aqueduct (LVA) syndrome, and one patient with X-linked deafness.

RESULTS

Standard transmastoid facial recess approach was used in 17 patients (three patients with IP I, four patients with IP II, and nine patients with LVA syndrome). In the remaining patient with IP I, because of the dehiscent and anteriorly located facial nerve, the surgical approach had to be modified, and an anteroposterior approach was used. After elevating the tympanomeatal flap, the electrode was inserted through the ear canal and then transferred to the mastoid through a full-length cut produced in the ear canal. The flap then returned to its place. In the patients with common cavity deformity, the electrode was inserted by the transmastoid labyrinthotomy approach. Facial nerve had an abnormal course in four patients, but no patient had facial weakness postoperatively. Cerebrospinal fluid gusher was encountered in four patients, whereas oozing was present in five patients. It seems that a slightly larger cochleostomy may reduce postoperative rhinorrhea. The patient with common cavity deformity showed abnormal vestibular stimulation which decreased and was totally abolished during a 3-month period.

CONCLUSION

Based on these findings, cochlear implantation is surgically feasible in patients with common cavity, IP types I and II, and LVA. The surgeon should be ready to make modifications in the surgical approach because of the abnormal course of the facial nerve and be ready to produce special precautions to cerebrospinal fluid gusher.

Hörvermögen bei Kindern und Jugendlichen mit Down-Syndrom

BACKGROUND

There are controversial opinions about the incidence of hearing impairment of children and adolescents with Down's syndrome as an additional cause for obstruction in social and communicative live. Next to congenital diseases of the inner ear, functional limitations can often lead to conductive hearing disorders in patients with Down's syndrome.

PATIENTS AND METHODS

The hearing ability, otoscopic and audiometric characteristics of 115 patients aged 3.2+/-2.9 years were analysed retrospectively over 42 months.

RESULTS

A total of 86 children showed morphologic otoscopic peculiarities: transitory evoked otoacoustic emissions (TEOAE) were often non-reproducible, even in patients with normal hearing abilities(14.1% of cases), and were not evaluable in 32.8% of cases. Half of the patients showed hearing loss, 82% of whom suffered from a conductive hearing loss, 6.9% from a combined, and 8.6% from isolated sensorineural hearing loss. Hearing loss was first diagnosed when the children were 4.6+/-3.4 years old.

CONCLUSION

The frequent occurrence of hearing loss justifies and requires an early and continuous pedaudiological examination. As a common screening examination, TEOAE is limited due to its cost, however, it fulfils its purpose as a means of distinguishing healthy children from those with possible hearing disorders. In most cases, objective and subjective audiometric methods must be combined in order to precisely define the hearing ability.

Cochlear implantation in children with anomalous cochleovestibular anatomy

OBJECTIVES/HYPOTHESIS

To evaluate outcomes after cochlear implantation in children with anomalous cochleovestibular anatomy, a review of radiological classification, surgical implantation, and outcome of 103 children with such anomalies was performed. The hypothesis was that children with anomalous cochleovestibular anatomy would have poorer outcomes and therefore be poorer candidates as a result of their diminished ability to interpolate and use auditory information delivered through a cochlear implant.

STUDY DESIGN

A series of studies was carried out to review the cochleovestibular anomalies among 298 children implanted over the decade ending in January 2002. Children were grouped based on cochleovestibular anatomy as follows: normal (n = 195), common cavity deformity (n = 8), hypoplastic cochlea (n = 16), incomplete partition (n = 42), and vestibular aqueduct enlargement (n = 37). Concomitant anomalies of the posterior labyrinth (n = 26) and internal auditory canal/cochlear canal (n = 11) were also identified. Findings at surgery, postoperative speech perception outcomes, and speech processor programmability were examined as a function of cochleovestibular anatomy.

METHODS

A database containing demographics (age at implant, duration of implant use), audiological characteristics, pure-tone average, surgical findings (cerebrospinal fluid leak/perilymph leak, abnormal facial nerve anatomy), speech perception data (from two closed-set and three open-set tests), and data relating to speech processor programmability were used for analysis. Electrically evoked auditory brainstem response was measured in 94 of the children (2 cases of common cavity deformity, 7 of hypoplastic cochlea; 10 of incomplete partition; and 12 of vestibular aqueduct enlargement). Response morphological findings were assessed by visual inspection of the waveforms. Data were analyzed using analyses of variance with post hoc testing using the Bonferroni multiple-comparisons test. To further assess differences in outcomes between different categories of cochleovestibular anomalies, linear regression analyses were performed. The significance level was set at P < .05.

RESULTS

The use of high-resolution imaging techniques resulted in the detection of a cochleovestibular anomaly in 35% of implanted ears. Implantation was more challenging in 24% of the children as a result of abnormal middle ear anatomy (17.5%) or cerebrospinal fluid leak/perilymph leak (6.7%). There was no significant difference in speech perception scores in children with anomalous cochleae compared with children with normal cochleovestibular anatomy. Children with narrowing of the internal auditory canal/cochlear canal performed more poorly than all other groups. Children with common cavity deformity and hypoplastic cochlea had reduced dynamic range and increased incidence of facial simulation and were judged to be more difficult to program despite the fact that no fewer electrodes were inserted. Children with common cavity deformity and hypoplastic cochlea tended to require wider pulse widths more often than children in other groups, and these requirements were associated with abnormal morphological findings on evoked auditory brainstem response testing.

CONCLUSION

The authors have been continuing to assess the candidacy of each child applying for cochlear implantation individually, and the results of present study have suggested that the presence of anomalous cochleovestibular anatomy, with the exception of narrowing of the internal auditory canal/cochlear canal, should not play a significant role in candidacy assessment. Children with narrow internal auditory canal/cochlear canal should be carefully and individually considered. In children with anomalous cochleovestibular anatomy, the potentially increased difficulty in the establishment of optimal stimulation levels and the higher potential for surgical difficulty must be weighed in candidacy decisions but do not universally preclude successful implantation and a good outcome.

Audiological performance after cochlear implantation in children with inner ear malformations

OBJECTIVES

To prove that cochlear implantation is a beneficial method of rehabilitation in deaf children with malformations of the inner ear.

DESIGN

The evaluation of auditory responses to speech (EARS) test battery was performed on the children in this study after an average implant use of 3 years.

RESULTS

Individual results of six children with inner ear anomalies receiving cochlear implants are presented in this study. Three of the patients showed an incomplete partition (Mondini dysplasia), one had a cochlear hypoplasia and two suffered from an intraoperative cerebrospinal fluid leak. The majority of the children in this study are successful implant users. Wherever possible, test scores are included and subjective case reports given.

CONCLUSIONS

Results are similar to those in children with normal cochleas, therefore inner ear malformations found in as many as 20% of patients with congenital sensorineural hearing loss are no contraindication for cochlear implantation. Nevertheless, factors influencing the success of implantation are multiple, including a thorough preoperative radiological examination, a well-performed surgery and an individually tailored postoperative rehabilitation programme.

Auditory late cortical response and speech recognition in Digisonic cochlear implant users

OBJECTIVE

The purpose of the study was to test for differences in late electrically evoked auditory potentials between subjects exhibiting "good" versus "poor" speech recognition performances with their cochlear implants.

METHODS

Late auditory evoked responses were measured in 30 subjects equipped with the Digisonic (MXM, Antibes, France) cochlear implant, 15 of whom had "good" speech recognition scores (i.e., more than 89% correct phoneme identification without lip reading). The 15 other subjects had poorer speech recognition scores (i.e., less than 85%).

RESULTS

Differences in N1P2 amplitude, as well as P1, N1, and P2 latencies, and N1-P1 and N1-P2 latency intervals were tested. Wave P2 latency was found to be significantly different between the two groups (P =.016), being shorter in "good" than in "poor" performers. The strength of the statistical relationship between electrophysiological and speech recognition variables (r2 = 17%) was substantially smaller than that observed using electrically evoked auditory brainstem response (EABR) for the same implanted device (r2 = 49% for the EABR wave III-V latency interval).

CONCLUSIONS

Some characteristics of late electrically evoked auditory potentials differ significantly among cochlear implant users depending on their speech recognition performance. However, the relationship between electrophysiological and speech recognition variables is more pronounced when early (brainstem) rather than late (cortical) evoked responses are considered.

Analysis of spiral ganglion cell populations in children with normal and pathological ears

This study analyzed features of total and segmental spiral ganglion cell populations in children with normal ears and those with various pathological conditions. Sixty-three human temporal bone specimens, obtained from 43 children 4 days to 9 years of age, were studied histopathologically. These specimens were divided into 5 diagnostic groups: group 1, normal ears (13 ears); group 2, congenital infectious diseases (13 ears); group 3, chromosomal aberrations (11 ears); group 4, multiple craniofacial anomalies with hereditary or genetic causes (21 ears); and group 5, perinatal and postnatal asphyxia (5 ears). Eighteen of the 63 ears had documented profound deafness. In either normal ears (group 1) or those with various pathological conditions (groups 2 through 5), the total number of ganglion cells did not change as a function of age during the first 10 years. The total number of ganglion cells was significantly larger in group 1 (33,702) than in each of groups 2, 3, 4, and 5 (p < .01), and the number was significantly larger in group 2 than in each of groups 4 and 5 (p < .01 and p < .05, respectively). The ratio of basal to apical ganglion cell populations remained constant in both normal and pathological ears. Each ratio of the number of basal and apical ganglion cells in groups 2, 3, 4, and 5 to the mean number in group 1 (basal and apical survival ratios) was at least approximately 40%. There was no statistical difference between these two ratios in groups 2, 3, 4, and 5. The mean (+/-SD) total number of ganglion cells in ears with documented profound deafness was 15,417 +/- 5,944, which is approximately 40% of those present in normal ears. Our results suggest that normally, cochlear neurons are completely present at birth and minimally regress during the first decade of life. In addition, although intergroup differences among various pathological groups were present, the majority of pathological ears had more than 10,000 spiral ganglion cells present. Cochlear implantation has gradually been recognized as an effective and reliable tool for rehabilitation of children who have profound deafness, even congenitally or prelingually deafened children. On the basis of the results obtained in this study, we discuss the implications for cochlear implantation in children.

Cochlear implantation in children with inner ear malformations: report of two cases

Cochlear implantation of congenitally deaf children with inner ear malformations is gaining special interest. Although the number of the reported cases is increasing, the decision for implantation needs thorough investigation. Preoperative evaluation, surgical approach and postoperative follow-up can be challenging.

STUDY DESIGN

A retrospective analysis of two cases with inner ear malformations.

PATIENTS

One patient was a 3-year-old-girl who had cochlear and cochleovestibular nerve aplasia on the left side and incomplete partition on the other side. The other patient was a 5-year-old-boy who had hypoplastic cochlea on both sides. Both of them also had vestibular anomalies. Cases were implanted by using multichannel cochlear implant.

RESULTS

No complications were encountered. Both patients responded to acoustic stimuli, and their speech perception skills were improved. After 10 months of cochlear implant use, their results seem encouraging.

CONCLUSION

Except cochlear or cochleovestibular nerve agenesis, inner ear malformations cannot be accepted as a contraindication for cochlear implantation. Although there can be difficulties during the surgery or in the postoperative period, patients with inner ear malformations can also benefit from cochlear implantation. It is essential that all possible complications and postoperative performance should be discussed with the parents.

Temporal bone histopathology related to cochlear implantation in congenital malformation of the bony cochlea

HYPOTHESIS

Histopathologic findings in temporal bones with congenital malformations of the bony cochlea may provide insight into cochlear implantation planning, surgical approach, and complications.

BACKGROUND

Patients with congenitally malformed cochleae account for an increasing percentage of candidates for cochlear implantation. Few studies on the relationship between histopathologic findings of temporal bones with malformation of the bony cochlea and cochlear implantation have been reported.

METHODS

We studied 21 temporal bones from 12 cases with congenital malformations of the bony cochlea. Ages ranged from stillborn to 50 years. Length of the cochleae and dimensions of facial recesses were measured with light microscopy. Other malformations associated with a shortened cochlea were determined, emphasizing how they affect cochlear implantation.

RESULTS

The average length of the malformed cochlear duct was 22.84 +/- 0.69 mm. Average dimensions of facial recesses were not significantly different between malformed cochleae and the controls. Other malformations included enlarged cochlear aqueduct (43%), abnormal facial nerve course (57%), enlarged vestibular aqueduct (52%), aplasia of the middle ear (19%), malformed ossicles (67%), abnormal oval window (57%), and abnormal round window (29%).

CONCLUSION

A shortened cochlear duct may cause an incomplete insertion of the implant electrode. Because dimensions of the facial recesses are similar to normal cases, a facial recess surgical approach is recommended. An enlarged cochlear aqueduct may cause perilymphatic oozing or gushing on fenestration of the cochlea. An anomalous course of the facial nerve is a common finding. Tympanic malformations such as round and oval window deformities and small middle ear cleft should be noted preoperatively to better guide surgery.

Increased cell death in the developing vestibulocochlear ganglion complex of the mouse after prenatal ethanol exposure

BACKGROUND

Previous studies have demonstrated that excessive prenatal alcohol exposure can damage the auditory and vestibular systems, in particular, cochlear hair cells. However, the direct effect of ethanol on the peripheral neurons in these pathways has not been examined. To study the effects of prenatal ethanol exposure on the developing vestibulocochlear ganglion (VCG) complex and the peripheral sensory organs, we exposed pregnant mice to ethanol and examined the levels of cell death in the inner ear.

METHODS

Pregnant C57BL/6J mice were administered one of three doses of either ethanol (3.0, 4.5, and 5.5 g/kg) or isocaloric maltose/dextrin via intragastric intubation on gestational day (GD) 12.5. Embryos were dissected out of the uterus 8 hr after the intubation. Dying cells in the inner ear were stained with Nissl stain and labeled by in situ terminal dUTP nick-end labeling (TUNEL), and the percentage of dying cells was quantified.

RESULTS

Ethanol exposure produced region-specific effects, with ethanol-exposed embryos exhibiting enhanced cell death only in the VCG complex, and not in the primitive saccule, cochlea, semicircular canal, or endolymphatic sac. The effects of ethanol on cell death in the VCG are dose dependent, with a significant increase in the level of cell death found only at the higher doses.

CONCLUSIONS

Ethanol has a selective cytotoxic dose-dependent effect on the VCG at GD 12.5 suggesting that loss of VCG neurons may contribute to hearing and /or vestibular abnormalities in FAS children. Furthermore, the presence of TUNEL-positive cells and DNA laddering is consistent with the cells undergoing apoptotic cell death.

Implantation of the malformed cochlea

OBJECTIVE

This study assesses the results of cochlear implantation in children with cochlear malformations.

STUDY DESIGN

Retrospective, matched-pairs analysis of prospectively collected data.

SETTING

University-based regional cochlear implant center.

PATIENTS

Seventeen children with osseous cochlear malformations who had undergone implantation were matched and compared with a group of children with normal cochleae who had undergone implantation.

INTERVENTIONS

All subjects received a multichannel cochlear implant and habilitation.

MAIN OUTCOME MEASURES

All subjects were tested with the Early Speech Perception test, and the Glendonald Auditory Speech Perception tests for words and sentences. Patients were classified in a standardized speech perception category based on performance on the Early Speech Perception test.

RESULTS

All subjects demonstrated improving performance on all measures of speech perception over time. Overall, the two groups showed no statistically significant differences in performance at 6 and 24 months. However, subjects with malformed cochleae evidenced slower rates of improvement than did their matched control subjects. Subjects with more severe malformations demonstrated poorer performance, but this may have been attributable to preoperative factors rather than to implant performance.

CONCLUSIONS

Children with radiographic cochlear malformations benefit from cochlear implantation with multichannel devices. They ultimately perform as well as their matched counterparts with normal cochleae, although they may improve more slowly over time.

The cochlear nuclei in two patients with Usher syndrome type I

HYPOTHESIS

Does long-term sound deprivation lead to degeneration of the cochlear nuclei in two Usher type I patients?

METHODS

The cochlear nuclei of these patients were morphometrically analyzed and compared with two age-matched controls. Routine autopsy of the brainstems was performed before the design of this study was known. During this procedure, the ventral cochlear nucleus (VCN) can easily be damaged. Five partially damaged VCN could nevertheless be analyzed for this study, including the right VCN of Usher patient 1 and both VCN of Usher patient 2. Using 15 microm thick serial paraffine sections of the cochlear nuclei, estimates of volume, neuronal densities, number of cells and mean cell diameter of the dorsal cochlear nucleus (DCN) and VCN were obtained.

RESULTS

This study presents unique material of the cochlear nuclei in two patients with Usher syndrome type I. Data regarding volume and total cell number of the VCN are influenced by the absence of a part of the VCN. Results suggest a decrease in mean cell diameter of the VCN in Usher patients. Other parameters of the VCN and DCN, however, showed no major differences between Usher type I patients and controls.

CONCLUSION

Only minor degenerative changes are apparent in the cochlear nuclei of two patients with Usher type I, who were deprived of acoustic stimuli since birth.

Multichannel cochlear implantation in children with large vestibular aqueduct syndrome

This study examined the postoperative performance of multichannel cochlear implantation in children with severe-to-profound sensorineural hearing loss secondary to large vestibular aqueduct syndrome. Five children between ages 4 and 13 years who had large vestibular aqueducts confirmed by computed tomography scans underwent implantation of a CLARION Multi-Strategy Cochlear Implant between January 1995 and June 1996 at Boys Town National Research Hospital. In addition to preoperative evaluations, they were examined postoperatively with their implants on a battery of open-set speech recognition tests at 3, 6, 12, and 18 months following initial stimulation. Results indicated a noticeable improvement in open-set speech recognition within the first 3 months of implant use compared to preimplant performance with hearing aids. All 5 patients demonstrated substantial benefit from their implants, but there was variation among the children in the rate and amount of improvement in speech recognition skills.

Cochlear implant performance and electrically-evoked auditory brain-stem response characteristics

OBJECTIVES

The purpose of this study was to find a correlation between cochlear implant performances in phoneme discrimination and activity of the brain-stem.

METHODS

Electrically-evoked auditory brain-stem responses (EABRs) and speech recognition performances were measured in 17 patients implanted with an MXM Digisonic DX10 cochlear implant. Speech recognition performances without lip-reading were tested using lists of isolated French words containing 3 phonemes.

RESULTS

The results indicated statistically significant correlations between phoneme correct-identification scores and the following EABR variables: wave V latency, wave II-V latency interval and wave III-V latency interval. These results, indicate that up to about 48% of the variance in isolated word recognition without lip-reading can be accounted for by EABR variables.

CONCLUSION

The quality of brain-stem functioning influences central processes in phoneme discrimination.

Cochlear Neuronal Loss as Determined by Use of a Neurofilament Protein Antibody in Cases of Bilateral Profound Deafness

The temporal bones of two patients with profound bilateral deafness from infancy were studied immunohistochemically, using a neurofilament protein antibody to detect the cochlear neuronal elements. One patient exhibited Mondini dysplasia of the inner ear, with the organ of Corti almost completely deteriorated. The other patient is the first reported case involving complete aplasia of the organ of Corti in all turns. In both cases, the immunohistochemical staining clearly revealed a severe reduction in the number of afferent neurons, such as dendrites, spiral ganglion cells and cochlear axons. The number of efferent spiral bundles in the osseous spiral lamina and intraganglionic portion also decreased in parallel with the reduction in the number of cochlear afferent neurons. Our results are inconsistent with previously reported cases of presbycusis and acquired deafness induced by the measles virus, in which efferent neurons were preserved while afferent neurons degenerated. The loss of both the efferent and afferent neurons might be characteristics of congenital deafness.

Cochlear implantation in children with inner ear malformations

We performed a case study and intervention study, with follow-up of 1 to 5 years, in 4 children with inner ear malformations who underwent implantation of a multichannel cochlear implant (Nucleus, Cochlear Corporation) at ages 3 to 12 years. Malformations included a common cavity deformity, 2 incomplete partitions, and 1 case of isolated bilateral vestibular aqueduct enlargement. One child had a single-channel implant placed at 3 years of age, and this was exchanged for a 22-channel implant at age 9. One child had her implant placed at age 4.5 years, but due to complications from a cerebrospinal fluid (CSF) leak had the initial implant removed and replaced at age 5 years during repair of the CSF leak. Intraoperative findings included a CSF leak at the time of surgery in 3 patients. One patient contracted bacterial meningitis 7 months postimplantation that was thought to be secondary to acute otitis media in the unoperated ear. Bilateral CSF leaks were noted in the middle ear by a lumbar puncture radionuclide and fluorescein dye study. Successful repair of the CSF leaks and reimplantation of the cochlear implant was carried out in this patient. Mapping and programming of the implant was found to be challenging in each of these patients. All patients demonstrated improved performance after implantation. Two patients demonstrated some open-set speech perception. One patient demonstrates improved use of temporal cues in a structured closed set. One patient has achieved no significant speech recognition at this time, but does have improved sound detection and awareness. Cochlear implantation in children with congenital inner ear abnormalities can be a successful method of rehabilitation. It should be recognized that the postoperative speech perception results may be highly variable among patients, and that intraoperative complications may occur.