Cochlear implantation under the first year of age – the outcomes. A critical systematic review and meta-analysis

Bottom-line conclusion: Neuroplasticity/neurolinguistic issues have led cochlear implant centers to implant deaf children in infancy; however, widespread policies regarding the aforementioned issue are still not justified. Evidence of these children’s outperformance regarding auditory perception/speech production outcomes is limited. Wide-range comparisons between infant implantees and under 2-year-old implanted children are lacking. Longer-term follow-up outcomes should be also made available. There is a need to develop and validate robust measures of monitoring implanted infants. Potential factors of suboptimal outcomes (e.g. misdiagnosis, additional disorders, device tuning, parental expectations) should also be weighted, when considering cochlear implantation in infancy.

Method: Literature-review from Medline and database sources. Related books were also included.

Results: The number of cohort-studies comparing implanted infants with under 2-year-old children was five; three represented type-III and two type-II evidence. No study was supported by type I evidence. Overall, 125 implanted infants were identified. Precise follow-up period was reported in 82. Median follow-up duration ranged between 6 and 12 months; only 17 children had follow-up duration equal or longer than 2 years. Reliable outcome measures were reported for 42 infants; 15 had been assessed with open/closed-set testing, 14 with developmental rating scales, and 13 with prelexical speech discrimination tools. Ten implanted infants assessed with open/closed-set measures had been compared with under 2-year-old implanted children; 4 had shown better performance, despite the accelerated rate of improvement after the first postoperative year.

from NHS Evidence

Depressive emotioning in adolescents with cochlear implant and normal hearing

Conclusions
As a result of these findings, it was thought that cochlear implantation had a positive effect on life quality and it was suggested that the adolescents and their families should get assistance from experts about the characteristics and principles of approaching the child in this period. The adolescent should be directed towards social activities and courses, their positive sides should be supported and further studies should be carried out with different case groups on this matter. In addition to, examining the interactions of hearing loss effects can help professionals determine the individuals who are at a higher risk for developing mental distress.

from the International Journal of Pediatric Otorhinolaryngology

The prelexical development in children implanted by 16 months compared with normal hearing children

Objective
Few studies exist which document the early speech development of German-speaking children or German-speaking children who are deaf and using cochlear implants. The current study aims to: (1) document the pre-canonical and canonical speech development of German-speaking children who are deaf and receive cochlear implants by the age of 16 months and (2) compare these children’s results with those of children with normal hearing.

Design
This longitudinal study included 5 German-speaking children with normal hearing and 5 with sensorineural deafness. All children from the deaf group received hearing amplification before cochlear implantation, received their first implant by 16 months of age, and became bilateral implant users by 31 months of age. The pre-canonical and canonical vocalisations of each child were recorded on video- and audiotapes in a semi-standardised playing situation every 4 weeks over a span of 1 year. In the cochlear implant group, the recording started 4–5 days postoperatively (first implant); in the normal hearing group it began between the ages of 4 and 5 months. The video and audio recordings were analysed using EUDICO Linguistic Annotator version 2.4 (Nijmegen, The Netherlands) and International Phonetic Alphabet transcription.

Results
Both groups showed individual patterns of babbling acquisition, though the groups’ patterns of acquisition were similar when analysed for consonant manner and place. Some children started with plosives and others, with nasals, but all acquired fricatives and laterals next. Onset of canonical babbling for children in the cochlear implant group began 0–4 months after first fitting of the first device, while children from the normal hearing group demonstrated an onset of canonical babbling between 4 and 9 months of age.

Conclusion
Our results show that deaf children who receive cochlear implants at an early age are capable of reaching the canonical babbling milestone in a shorter time than children with normal hearing typically do and that their consonant phoneme acquisition follows a similar sequence to normal hearing peers’. These results are consistent with the literature indicating that early identification and intervention are important for allowing children with cochlear implants the opportunity to catch up to hearing peers.

from the International Journal of Pediatric Otorhinolaryngology

Mutation of OPA1 gene causes deafness by affecting function of auditory nerve terminals

Abstract
Autosomal dominant optic atrophy (DOA) is a retinal neuronal degenerative disease characterized by a progressive bilateral visual loss. We report on two affected members of a family with dominantly inherited neuropathy of both optic and auditory nerves expressed by impaired visual acuity, moderate pure tone hearing loss, and marked loss of speech perception. We investigated cochlear abnormalities accompanying the hearing loss and the effects of cochlear implantation. We sequenced OPA1 gene and recorded cochlear receptor and neural potentials before cochlear implantation. Genetic analysis identified R445H mutation in OPA1 gene. Audiological studies showed preserved cochlear receptor outer hair cell activities (otoacoustic emissions), and absent or abnormally delayed auditory brainstem responses (ABRs). Trans-tympanic electrocochleography (ECochG) showed prolonged low amplitude negative potentials without auditory nerve compound action potentials. The latency of onset of the cochlear potentials was within the normal range found for inner hair cell summating receptor potentials. The duration of the negative potential was reduced to normal during rapid stimulation consistent with adaptation of neural sources generating prolonged cochlear potentials. Both subjects had cochlear implants placed with restoration of hearing thresholds, speech perception, and synchronous activity in auditory brainstem pathways. The results suggest that deafness accompanying this OPA1 mutation is due to altered function of terminal unmyelinated portions of auditory nerve. Electrical stimulation of the cochlea activated proximal myelinated portions of auditory nerve to restore hearing.

from Brain Research

A systematic review to determine the effectiveness of using amplification in conjunction with cochlear implantation

Method: RESEARCH DESIGN: A systematic review of the evidence that met the search criteria related to the use of amplification in adult implant users. All types of experiments were included with the exception of expert opinion. This systematic review ranked the levels of evidence related to these studies and distinguished the levels of evidence from judgments about the grade and strength of recommendations for the stated clinical question. STUDY SAMPLE: Fifty-two articles were initially reviewed with a final 11 articles meeting the search criteria and identified for in-depth analysis. DATA COLLECTION AND ANALYSIS: Several electronic databases and textbooks were searched to locate the evidence related to bimodal stimulation. Each article was reviewed using a check sheet and assigned a ranking for level of evidence (Levels 1-6) based on the type of research design that was used and a grade of evidence (A-D) based on the quality, relevance, and extensiveness of the study. Finally the level and grade were collapsed into only three categories to indicating the strength of the recommendations coming from each study and were classified as either strong (I), moderate (II), or weak (III).

Results: Several trends about bimodal stimulation were observed, which include (1) significantly better speech understanding in the bimodal condition for many participants; (2) in noise, the largest bimodal benefits in speech recognition; (3) variable findings on localization tasks; and (4) overall significant improvement in functional ability based on self-assessments. The preponderance of evidence received grades of B or C.

from

Effectiveness of multi-channel unilateral cochlear implants for profoundly deaf children: a systematic review

Method: This examined 16 electronic data bases, plus bibliographies and references for published and unpublished studies. Abstracts were independently assessed against inclusion criteria by two researchers, results were compared and disagreements resolved. Included papers were then retrieved and further independently assessed in a similar way. Remaining studies had their data independently extracted by one of five reviewers and checked by another reviewer.

Results: From 1,580 abstracts and titles 15 studies were included. These were of moderate to poor quality. The large amount of heterogeneity in design and outcomes precluded meta-analysis. However, all studies reported that unilateral cochlear implants improved scores on all outcome measures. Additionally five economic evaluations found unilateral cochlear implants to be cost-effective for profoundly deaf children at UK implant centres.

from

Cochlear implantation in the very young child: Long-term safety and efficacy

Cochlear implantation in children <12 months of age is safe and efficacious over an extended period of time. Rates and nature of both major and minor complications are comparable to studies in adults and older children and support continued monitoring of these patients over the long-term. Laryngoscope, 2009

from The Laryngoscope

An evaluation of the preservation of residual hearing with the Nucleus® Contour Advance™ electrode

Conclusion. Our study results confirm that it is possible to preserve preoperative hearing levels in the majority of subjects when using the Nucleus 24 Contour Advance provided that there is adherence to the major principles of ’soft surgery’. Our study group demonstrated that 71-86% of subjects showed preservation of preoperative hearing thresholds at 6 months to varying degree. Objectives. The aim of the study was to assess the degree of residual hearing preserved postoperatively in a group of standard cochlear implant (CI) candidates following implantation via soft surgery with a Nucleus® 24 Contour Advance™ CI. Surgical technique variations from the soft surgery guidelines provided were assessed and their potential impact upon the conservation of residual hearing was examined. Subjects and methods. A prospective multicentre study involving a within-subject repeated measures design with each subject acting as their own control was performed. Pure-tone audiometric thresholds were assessed and compared in both implanted and contralateral ears for each subject preoperatively as baseline measures and at 6 months postoperatively. Surgeons were asked to complete a questionnaire to capture various aspects of the surgical technique used for each subject. Variations in the surgical technique performed were examined for potential correlation with conservation of residual hearing. Twenty-eight adult subjects, with a severe to profound hearing impairment, were enrolled in the study across eight implant clinics in four countries. Results. In all, 36% of subjects demonstrated preservation of thresholds to within 10 dB of preoperative thresholds across the frequency range (0.25, 0.5, 1.0, 2.0 and 4.0 KHz) and for the low frequency range (0.25-1.0 KHz). Approximately two-thirds of subjects demonstrated preservation of preoperative thresholds to within 20 dB. Preservation of low frequency thresholds post-implant was shown to correlate moderately with cochleostomy site, being more likely for subjects with a site anterior-inferior to the round window but also possible with inferior locations; weakly with cochleostomy size, being more likely when smaller than 1.2 mm; and also with the use of Healon® as a sealant and lubricant. Preservation of hearing thresholds across up to 4000 Hz was shown to correlate weakly with the use of suction following opening of the endostium and with bone dust contamination, both having a negative effect upon preservation, while no correlation was observed with the preservation of thresholds for low frequencies alone.

from Acta Oto-Laryngologica

Lexical tone identification and consonant recognition in acoustic simulations of cochlear implants

Conclusion: Cochlear implant (CI) recipients’ performance of lexical tone identification and consonant recognition can be enhanced by providing greater spectral details. Objective: To evaluate the effects of increasing the number of total spectral channels on the lexical tone identification and consonant recognition by normally hearing listeners who are native speakers of Mandarin Chinese. Subjects and methods: Lexical tone identification and consonant recognition were measured in 15 Mandarin-speaking, normal-hearing (NH) listeners with varied numbers of total spectral channels (i.e. 4, 6, 8, 10, 12, 16, 20, and 24), using acoustic simulations of CIs. Results: The group of NH listeners’ performance of lexical tone identification ranged from 44.53% to 66.60% with 4-24 spectral channels. The performance of tone identification between channels 4 and 16 remained similar; between channels 16 and 20 performance improved significantly. As regards consonant recognition, the NH listeners’ overall accuracy ranged from 73.17% to 95.33% with 4-24 channels. Steady improvement in consonant recognition accuracy was observed as a function of increasing the spectral channels. With about 12-16 spectral channels, the NH listeners’ overall accuracy in consonant recognition began to be comparable to their accuracy with the unprocessed stimuli.

from Acta Oto-Laryngologica

Impact of Low-Frequency Hearing

Today, cochlear implantation is the treatment of choice in the case of severe to profound hearing loss, but the speech perception abilities of many recipients in noisy conditions are still poor and the overall sound quality and ease of listening still require improvement. Residual low-frequency hearing has been associated with improved hearing performance in cochlear implant patients, especially in difficult listening environments (i.e. cocktail party effect). It seems that low-frequency information can enhance the segregation of competing voices, which leads to better speech understanding in noise. We investigated the effect of low-frequency hearing on speech perception performance in a group of subjects being implanted with the Nucleus Hybrid-L device. The Hybrid-L device is a modified Nucleus Freedom implant, which instead of the standard electrode carries a very delicate electrode array that allows preservation of residual hearing to a great extent. Sentence test results from 22 subjects are presented here. Additionally, for 8 subjects, the acoustically presented frequency range was limited to 300, 500 and 700 Hz, and speech perception tests with a single competing talker were conducted. The Hybrid-L study group achieved a speech reception threshold of 15.9 dB in the hearing aid alone condition, 10.8 dB in the cochlear implant alone condition, and 3.9 dB when using the combination of cochlear implant and hearing aid. Differences between the 3 conditions are statistically significant. Results from the additional experiment on the acoustically presented frequency range suggest that very limited residual hearing below 500 Hz is already sufficient to produce a significant improvement in speech perception performance in conjunction with a cochlear implant.

from Audiology & Neuro-Otology

Results of Partial Deafness Cochlear Implantation Using Various Electrode Designs

Nineteen adults and 9 children who received a unilateral cochlear implant between 2002 and 2007 were included in the study. All subjects were preoperatively diagnosed with significant residual hearing in low frequencies, termed as ‘partial deafness’, and were implanted according to a 6-step round window surgical technique for partial deafness cochlear implantation. Hearing was preserved to a great extent in the partial deafness cochlear implantation (PDCI) group. After a short period following activation of the cochlear implant, highly significant improvement in the recognition of monosyllabic words was observed. With a developed round window surgical procedure and limited electrode insertion, hearing can be preserved in the majority of patients with partial deafness. PDCI is a feasible means of treating individuals who have good low-frequency hearing but severe to profound hearing loss in the mid to high frequencies.

from Audiology & Neuro-Otology

Electro-Acoustic Stimulation

For simultaneous acoustic and electric stimulation to be perceived as complementary, it may be beneficial for hearing aids and cochlear implants (CI) to be adjusted to provide compatible pitch sensations. To this end, estimates of the pitch perceived for a set of acoustic and electric stimuli were obtained from 14 CI users who had usable low-frequency hearing, either in the non-implanted ear or in both ears. The subjects assigned numerical pitch estimates to each of 5 acoustic pure tones and 5 single-electrode electric pulse trains. On average, the acoustic frequency that corresponded in pitch to stimulation on the most apical electrode was approximately 480 Hz. This was about 1 octave lower than the frequency expected from Greenwood’s frequency-place function applied to estimates of the electrode insertion angle based on X-ray images. Furthermore, evidence was found suggesting that pitch decreased with increasing duration of CI use. Pitch estimates from 5 subjects who completed the experiment before experiencing any other sounds through their CI were generally close to the values expected from a recently published frequency map for the cochlear spiral ganglion. Taken together, these findings suggest that some perceptual adaptation may occur that would compensate in part for the apparent mismatch between the intracochlear position of the electrodes and the acoustic frequencies assigned to them in the sound processor.

from Audiology & Neuro-Otology

Virtual Channel Discrimination is Improved by Current Focusing in Cochlear Implant Recipients.

Cochlear implant users’ spectral resolution is limited by both the number of implanted electrodes and channel interactions between electrodes. Current steering (virtual channels) between two adjacent monopolar electrodes has been used to increase the number of spectral channels across the electrode array. However, monopolar stimulation is associated with large current spread and increased channel interaction. Current focusing across three adjacent electrodes (tripolar stimulation) has been used to reduce electrode current spread and improve channel selectivity. In the present study, current steering and current focusing were combined within a four-electrode stimulation pattern (quadrupolar virtual channels), thereby addressing the need for both increased channels and reduced current spread. Virtual channel discrimination was measured in 7 users of the Advanced Bionics Clarion II or HiRes 90K implants; virtual channel discrimination was compared between monopolar and quadrupolar virtual channels at three stimulation sites. The results showed that quadrupolar virtual channels provided better spectral resolution than monopolar virtual channels. The results suggested that quadrupolar virtual channels might provide the “best of both worlds” improving the number of spectral channels while reducing channel interactions.

from Hearing Research

Cortical development, plasticity and re-organization in children with cochlear implants

A basic tenet of developmental neurobiology is that certain areas of the cortex will re-organize, if appropriate stimulation is withheld for long periods. Stimulation must be delivered to a sensory system within a narrow window of time (a sensitive period) if that system is to develop normally. In this article, we will describe age cut-offs for a sensitive period for central auditory development in children who receive cochlear implants. We will review de-coupling and re-organization of cortical areas, which are presumed to underlie the end of the sensitive period in congenitally deaf humans and cats. Finally, we present two clinical cases which demonstrate the use of the P1 cortical auditory evoked potential as a biomarker for central auditory system development and re-organization in congenitally deaf children fitted with cochlear implants.

from the Journal of Communication Disorders

Evoked cortical activity and speech recognition as a function of the number of simulated cochlear implant channels

Conclusions
P1–N1–P2 responses can be recorded using CVC syllables and there is an effect of channel number on the latency and amplitude of these responses, as well as on vowel identification. However, the physiological detection of the acoustic changes does not fully account for the perceptual performance of these same syllables.

Significance
These results provide evidence that it is possible to use vocoded CVC stimuli to learn more about the physiological detection of acoustic changes contained within speech syllables, as well as to explore brain–behavior relationships.

from Clinical Neurophysiology