Electrical Auditory Brainstem Response Research Articles

Intracochlear sound sensor-electrode system for fully implantable cochlear implant

We designed, fabricated, and tested an intracochlear sound sensor-electrode system consisting of an intracochlear sound sensor (ISS) and a 50μm Pt-Ir wire electrode. This system was designed to sense acoustic signals and transmit electrical stimuli inside the cochlea. Potential applications include acting as the front end of a fully implantable cochlear implant to treat sensorineural deafness or as a transducer in cochlear mechanics experiments. The ISS was comprised of an array of piezoelectric cantilevers and was built using micro-electrical-mechanical-system (MEMS) techniques. The ISS was tested in air and underwater to compare its functionalities to the numerical predictions. Later, the ISS was implanted in an anesthetized guinea pig and tested in vivo. A 90-100dB SPL pure tone acoustic excitation over 1-30kHz was delivered into the ear canal of the guinea pig, and 0.1-30μV was measured by the ISS. The sensed signal was linear, repeatable, and immune to the electrical interference from the extracochlear and intracochlear environment. When using the electrode, electrical auditory brainstem response (eABR) measurements were performed by sending a 25μs single pulse stimulus to the electrode. Stimulus amplitudes ranging in 220-400μA were found to evoke an eABR. These results show that the concept of sensing acoustic signals and transmitting electrical stimulation inside the living cochlea using one device is feasible.

Long-term Results of ABI in Children With Severe Inner Ear Malformations.

To report the long-term outcomes of children who received auditory brainstem implant (ABI) because of severe inner ear malformations. Retrospective chart review. Tertiary referral otolaryngology clinic. Between July 2006 and October 2014, 60 children received ABI at Hacettepe University. Preoperative work up included otolaryngologic examination, audiological assessment, radiological evaluation together with assessment of language development and psychological status. The surgeries were performed via retrosigmoid approach with a pediatric neurosurgeon. Intraoperatively, electrical auditory brainstem response was utilized. Initial stimulation was done 4 to 5 weeks postoperatively. Outcomes were evaluated with Categories of Auditory Performance (CAP), speech intelligibility rate (SIR), functional auditory performance of cochlear implant (FAPCI) and Manchester Spoken Language Development Scale scores; receptive and expressive language ages were determined. Sixty children who received ABI were between ages of 12 and 64 months. Thirty-five patients with follow up period of at least 1 year, were reported in means of long-term audiological and language results. The most prevelant inner ear malformation was cochlear hypoplasia (n = 19). No major complication was encountered. Majority of the patients were in CAP 5 category, which implies that they can understand common phrases without lip reading. SIR was found out to be better with improving hearing thresholds. Children with ABI were performing worse than average cochlear implantation (CI) users when FAPCI scores were compared. Patients with the best hearing thresholds have expressive vocabulary of 50 to 200 words when evaluated with Manchester Spoken Language Development Scale. There was no relationship between the number of active electrodes and hearing thresholds. The type of inner ear anomaly with the best and the worst hearing thresholds were common cavity and cochlear aperture aplasia, respectively. Patients with additional handicaps had worse outcomes. Among 35 children, 29 had closed set discrimination and 12 developed open set discrimination above 50%. It was determined that, progress of the patients is faster in the initial 2 years when compared with further use of ABI. ABI is an acceptable and effective treatment modality for pediatric population with severe inner ear malformations. Bilateral stimulation together with CI and contralateral ABI should be utilized in suitable cases.

Cochlear Implant Outcomes in Cochlea Nerve Aplasia and Hypoplasia.

To assess cochlear implant (CI) outcomes, and factors affecting outcomes, for children with aplasia/ hypoplasia of the cochlea nerve. We also developed a new grading system for the nerves of the internal auditory meatus (IAM) and cochlea nerve classification. Retrospective patient review. Tertiary referral hospital and cochlear implant program. Children 0 to 16 years inclusive with a CI who had absent/hypoplastic cochlea nerve on magnetic resonance imaging (MRI). Cochlear implant. MRI, trans-tympanic electrical auditory brainstem response, intraoperative electrical auditory brainstem response, Neural Response Telemetry, Categories of Auditory Perception score, Main mode of communication. Fifty CI recipients (26 males and 24 females) were identified, 21 had bilateral CIs, 27 had developmental delay. MRI showed cochlea nerve aplasia in 64 ears, hypoplasia in 25 ears, and a normal nerve in 11 ears. Main mode of communication was analyzed for 41 children: 21 (51%) used verbal language (15 speech alone, 5 speech plus some sign, 1 bilingual in speech and sign), and 20 (49%) used sign language (10 sign alone, 9 sign plus some speech, 1 tactile sign). Seventy-three percent of children used some verbal language. Cochlea nerve aplasia/ hypoplasia and developmental delay were both significant factors affecting main mode of communication. Categories of Auditory Performance scores were available for 59 CI ears; 47% with CN Aplasia (IAM nerve grades 0-III) and 89% with CN hypoplasia (IAM nerve grade IV) achieved Categories of Auditory Performance scores of 5 to 7 (some verbal understanding) (p = 0.003). Our results are encouraging and useful when counselling families regarding the likelihood of language outcomes and auditory understanding.

A Cochlear Implant Performance Prognostic Test Based on Electrical Field Interactions Evaluated by eABR (Electrical Auditory Brainstem Responses)

BackgroundCochlear implants (CIs) are neural prostheses that have been used routinely in the clinic over the past 25 years. They allow children who were born profoundly deaf, as well as adults affected by hearing loss for whom conventional hearing aids are insufficient, to attain a functional level of hearing. The “modern” CI (i.e., a multi-electrode implant using sequential coding strategies) has yielded good speech comprehension outcomes (recognition level for monosyllabic words about 50% to 60%, and sentence comprehension close to 90%). These good average results however hide a very important interindividual variability as scores in a given patients’ population often vary from 5 to 95% in comparable testing conditions. Our aim was to develop a prognostic model for patients with unilateral CI. A novel method of objectively measuring electrical and neuronal interactions using electrical auditory brainstem responses (eABRs) is proposed.Methods and FindingsThe method consists of two measurements: 1) eABR measurements with stimulation by a single electrode at 70% of the dynamic range (four electrodes distributed within the cochlea were tested), followed by a summation of these four eABRs; 2) Measurement of a single eABR with stimulation from all four electrodes at 70% of the dynamic range. A comparison of the eABRs obtained by these two measurements, defined as the monaural interaction component (MIC), indicated electrical and neural interactions between the stimulation channels.Speech recognition performance without lip reading was measured for each patient using a logatome test (64 "vowel-consonant-vowel"; VCV; by forced choice of 1 out of 16). eABRs were measured in 16 CI patients (CIs with 20 electrodes, Digisonic SP; Oticon Medical ®, Vallauris, France).Significant correlations were found between speech recognition performance and the ratio of the amplitude of the V wave of the eABRs obtained with the two measurements (Pearson's linear regression model, parametric correlation: r2 = 0.26, p<0.05).ConclusionsThis prognostic model allowed a substantial amount of the interindividual variance in speech recognition scores to be explained. The present study used measurements of electrical and neuronal interactions by eABR to assess patients' bio-electric capacity to use multiple information channels supplied by the implant. This type of prognostic information may be valuable in several ways. On the patient level, it allows customizing of individual treatments.ClinicalTrials.gov Identifier: NCT01805167

Electrical auditory brainstem responses during cochlear implantation

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SMAD4 Defect Causes Auditory Neuropathy Via Specialized Disruption of Cochlear Ribbon Synapses in Mice.

More than 100 genes have been associated with deafness. However, SMAD4 is rarely considered a contributor to deafness in humans, except for its well-defined role in cell differentiation and regeneration. Here, we report that a SMAD4 defect in mice can cause auditory neuropathy, which was defined as a mysterious hearing and speech perception disorder in human for which the genetic background remains unclear. Our study showed that a SMAD4 defect induces failed formation of cochlear ribbon synapse during the earlier stage of auditory development in mice. Further investigation found that there are nearly normal morphology of outer hair cells (OHCs) and post-synapse spiral ganglion nerves (SGNs) in SMAD4 conditional knockout mice (cKO); however, a preserved distortion product of otoacoustic emission (DPOAE) and cochlear microphonic (CM) still can be evoked in cKO mice. Moreover, a partial restoration of hearing detected by electric auditory brainstem response (eABR) has been obtained in the cKO mice using electrode stimuli toward auditory nerves. Additionally, the ribbon synapses in retina are not affected by this SMAD4 defect. Thus, our findings suggest that this SMAD4 defect causes auditory neuropathy via specialized disruption of cochlear ribbon synapses.

Auditory Rehabilitation in Rhesus Macaque Monkeys (Macaca mulatta) with Auditory Brainstem Implants.

Background:The auditory brainstem implants (ABIs) have been used to treat deafness for patients with neurofibromatosis Type 2 and nontumor patients. The lack of an appropriate animal model has limited the study of improving hearing rehabilitation by the device. This study aimed to establish an animal model of ABI in adult rhesus macaque monkey (Macaca mulatta).Methods:Six adult rhesus macaque monkeys (M. mulatta) were included. Under general anesthesia, a multichannel ABI was implanted into the lateral recess of the fourth ventricle through the modified suboccipital-retrosigmoid (RS) approach. The electrical auditory brainstem response (EABR) waves were tested to ensure the optimal implant site. After the operation, the EABR and computed tomography (CT) were used to test and verify the effectiveness via electrophysiology and anatomy, respectively. The subjects underwent behavioral observation for 6 months, and the postoperative EABR was tested every two weeks from the 1st month after implant surgery.Result:The implant surgery lasted an average of 5.2 h, and no monkey died or sacrificed. The averaged latencies of peaks I, II and IV were 1.27, 2.34 and 3.98 ms, respectively in the ABR. One-peak EABR wave was elicited in the operation, and one- or two-peak waves were elicited during the postoperative period. The EABR wave latencies appeared to be constant under different stimulus intensities; however, the amplitudes increased as the stimulus increased within a certain scope.Conclusions:It is feasible and safe to implant ABIs in rhesus macaque monkeys (M. mulatta) through a modified suboccipital RS approach, and EABR and CT are valid tools for animal model establishment. In addition, this model should be an appropriate animal model for the electrophysiological and behavioral study of rhesus macaque monkey with ABI.

Prognostic value of electrically evoked auditory brainstem responses in cochlear implantation

ObjectivesThe aim of this study was to investigate whether electrical auditory brainstem responses (eABRs) obtained during cochlear implantation (CI) can predict CI outcomes. We also aimed to assess whether eABR can be used to select patients for auditory brainstem implantation (ABI).MethodsThis was a retrospective study. The latencies and quality of the eABR waveforms from adult patients implanted with CI in Uppsala from 2011 to 2013 (n = 74) and four children with severe cochlear abnormalities were analyzed. Speech perception was assessed through postoperative monosyllabic word (MS-word) recognition. A score was constructed for each patient based on wave II, III, and V patency.ResultseABR latencies increased towards base stimulation of the cochlea. Wave V for the mid- and low-frequency regions was the most robust. Significant latency shifts occurred in wave V from the low- to high-frequency regions (**P < 0.01) and from the mid- to high-frequency regions (**P < 0.01). No correlations were found between waveform score, wave V–III interval, wave V latency, and MS-word scores. A negative eABR always predicted a negative outcome. Among the patients with negative outcomes, 75% had eABRs.DiscussionImplant electrical stimulation and brain stem recordings can be used (eABRs wave V) to predict a negative functional outcome. Low-frequency waves V were observed in all patients with successful CI outcomes. Patients for whom eABR waveforms were completely absent had unsuccessful CI outcomes.

Electric auditory brainstem response (E-ABR) in cochlear implant children: Effect of age at implantation and duration of implant use

AimThe objective of this study is to obtain stable and accurate electrically evoked auditory brainstem responses (EABR) in cochlear implant children and to evaluate the effect of age at implantation and duration of implant use on these responses. Method30 Children were implanted with Nucleus 24 cochlear implant. EABR recording were performed to all subjects using a stimulus with pulse width of 25μs/phase. The EABR signals were recorded from two electrodes (electrode 5 and 20) and at different intensities. The latency of the EABR waves III and V, and the EABR threshold were measured and analyzed. ResultsEABR waves could be recorded in 93.3% of the studied subjects. This study indicated better EABR responses at electrode 20 (apical electrode) relative to the basal site (electrode 5). EABR responses in children did not differ from adult responses. Moreover, the age of implantation and duration of implant use were correlated with EABR wave latencies and thresholds. ConclusionA well-established EABR was obtained in cochlear implant children with proper parameters. The characterizations of the EABR waves including wave latencies and threshold were extracted at different electrodes. The EABR test proves to be an effective method to evaluate the functions of the auditory pathway in children after cochlear implantation.

CHARGE syndrome and Cochlear implantation: Difficulties and outcomes in the paediatric population

ObjectivesCHARGE syndrome is a complex cluster of congenital abnormalities, these children may have absent or hypoplastic auditory nerves. Our objective was to assess preoperative factors and outcomes for paediatric cochlear implant recipients with CHARGE syndrome, to enable better surgical preparation and family counselling. MethodsThe Sydney Cochlear Implant Centre database was searched for children with CHARGE syndrome who had received a cochlear implant at ages 16 and less. Data were collected regarding clinical history; hearing assessments; MRI and CT scan findings; preoperative transtympanic electrical Auditory Brainstem Response (ABR); intraoperative findings and intraoperative electrical ABR and Neural Response Telemetry; and language outcomes in terms of main language used and Categories of Auditory Performance scores (0–7 ranking). ResultsTen children were identified. All seven prelingual profoundly deaf children with CHARGE syndrome had hypoplastic or absent auditory nerves bilaterally on MRI scans. Middle ear anatomy was often abnormal, affecting surgical landmarks and making identification of the cochlea very difficult in some cases. Three cases required repeated surgery to obtain successful cochlear implant insertion, one under CT scan image guided technique. All seven children used sign language, or simpler gestures, as their main mode of communication. Two children of of these children, who were implanted early, also attained some spoken language. CAP scores ranged from 0 to 6.The three children with CHARGE syndrome and progressive sensorineural hearing loss had a normal auditory nerve in at least one ear on MRI scans. All had preoperative verbal language, with CAP scores of 6, and continued with CAP scores of 6 following receipt of the cochlear implant. ConclusionChildren with CHARGE and congenital profound hearing loss all had hypoplasia or absent auditory nerves, affecting their outcomes with cochlear implants. They often had markedly abnormal middle ear anatomy and CT image guided surgery can be helpful. These children should be offered a bilingual early intervention approach, using sign language and verbal language, to ensure best language outcomes. Children with CHARGE syndrome and progressive profound hearing loss did well with cochlear implants and continue to be able to use verbal language.

Mapping of Paediatric Cochlear Implant Recipients using EABR as a Tool

Mapping of Paediatric Cochlear Implant Recipients using EABR as a Tool Objective: With expanding cochlear implant candidacy criteria young children, children with additional co-morbidities and abnormal cochlea are being implanted. In many of these cases, the child’s behavioural or cognitive limitations may make doing the task of behavioural mapping difficult or impossible in paediatric cochlear implant recipients (CIR). Therefore, the present study was aimed to determine whether behavioural thresholds could be predicted from objective measurements of electrical auditory brainstem responses (EABR). Methods: 75 paediatric CIR using Nucleus 24 R (ST) implant and operated and visiting the cochlear implant centre of a tertiary care hospital in New Delhi, India were prospectively enrolled in the study. The correlation between post-operative t- EABR with behaviourally obtained T and C levels was studied for CIR in the age range of 5-9 years. Statistical Analysis: The significance of correlation was calculated using Karl Pearson’s correlation. Results: Mean age of CIR was 9 ± 1.6 years, with M:F :: 38:37. Out of the 75 recipients one had mondini deformity and two subjects had auditory neuropathy spectrum disorder as per their medical records. The group correlation coefficient was found to be r=0.989 at p<0.0001 for the ‘T’ level and r=0.885 at p<0.0001 for ‘C’ level versus t-EABR (threshold EABR). Conclusion: t-EABR was found to be more correlated with T levels than with C levels and it was always between T and C levels.

Mapping of pediatric cochlear implant recipients using electrical auditory brainstem responses as a tool

Objective: With expanding cochlear implant (CI) candidacy criteria young children, children with additional co-morbidities and abnormal cochlea are being implanted. In many of these cases, the child's behavioral or cognitive limitations may make doing the task of behavioral mapping difficult or impossible in pediatric CI recipients (CIR). Therefore, the present study was aimed to determine whether behavioral thresholds (T) could be predicted from objective measurements of electrical auditory brainstem responses (EABR). Methodology: Seventy-five pediatric CIR using nucleus 24 R (ST) implant and operated and visiting the CI center of a tertiary care hospital in New Delhi, India were prospectively enrolled in the study. The correlation between postoperative thresholds-EABR (t-EABR) with behaviorally obtained T and C levels was studied for CIR in the age range of 5-9 years. Statistical Analysis: The significance of the correlation was calculated using Karl Pearson's correlation. Results: Mean age of CIR was 9 ± 1.6 years, with male: female: 38:37. Of the 75 recipients, one had Mondini deformity, and two subjects had auditory neuropathy spectrum disorder as per their medical records. The group correlation coefficient was found to be r = 0.989 at P < 0.0001 for the T level and r = 0.885 at P < 0.0001 for C level versus t-EABR. Conclusion: t-EABR was found to be more correlated with T levels than with C levels, and it was always between T and C levels.

Improved outcomes in auditory brainstem implantation with the use of near-field electrical compound action potentials.

To compare the outcomes (auditory threshold and open-set speech perception at 48-month follow-up) of a new near-field monitoring procedure, electrical compound action potential, on positioning the auditory brainstem implant electrode array on the surface of the cochlear nuclei versus the traditional far-field electrical auditory brainstem response. Retrospective study. Tertiary referral center. Among the 202 patients with auditory brainstem implants fitted and monitored with electrical auditory brainstem response during implant fitting, 9 also underwent electrical compound action potential recording. These subjects were matched retrospectively with a control group of 9 patients in whom only the electrical auditory brainstem response was recorded. Electrical compound action potentials were obtained using a cotton-wick recording electrode located near the surface of the cochlear nuclei and on several cranial nerves. Significantly lower potential thresholds were observed with the recording electrode located on the cochlear nuclei surface compared with the electrical auditory brainstem response (104.4 ± 32.5 vs 158.9 ± 24.2, P = .0030). Electrical brainstem response and compound action potentials identified effects on the neighboring cranial nerves on 3.2 ± 2.4 and 7.8 ± 3.2 electrodes, respectively (P = .0034). Open-set speech perception outcomes at 48-month follow-up had improved significantly in the near- versus far-field recording groups (78.9% versus 56.7%; P = .0051). Electrical compound action potentials during auditory brainstem implantation significantly improved the definition of the potential threshold and the number of auditory and extra-auditory waves generated. It led to the best coupling between the electrode array and cochlear nuclei, significantly improving the overall open-set speech perception.

The relationship between electrical auditory brainstem responses and perceptual thresholds in Digisonic® SP cochlear implant users

Determining the electrical stimulation levels is often a difficult and time-consuming task because they are normally determined behaviorally – a particular challenge when dealing with pediatric patients. The evoked stapedius reflex threshold and the evoked compound action potential have already been shown to provide reasonable estimates of the C- and T-levels, although these estimates tend to overestimate the C- and T-levels. The aim of this study was to investigate whether the evoked auditory brainstem response (eABR) can also be used to reliably estimate a patient's C- and T-levels. The correlation between eABR detection thresholds and behaviorally measured perceptual thresholds was statistically significant (r = 0.71; P < 0.001). In addition, eABR Wave-V amplitude increased with increasing stimulation level for the three loudness levels tested. These results show that the eABR detection threshold can be used to estimate a patient's T-levels. In addition, Wave-V amplitude could provide a method for estimating C-levels in the future. The eABR objective measure may provide a useful cochlear implant fitting method – particularly for pediatric patients.

Mapping of Paediatric Cochlear Implant Recipients using EABR as a Tool

Objective: With expanding cochlear implant candidacy criteria young children, children with additional co-morbidities and abnormal cochlea are being implanted. In many of these cases, the child's behavioural or cognitive limitations may make doing the task of behavioural mapping difficult or impossible in paediatric cochlear implant recipients (CIR). Therefore, the present study was aimed to determine whether behavioural thresholds could be predicted from objective measurements of electrical auditory brainstem responses (EABR).

The management of cochlear nerve deficiency

The assessment process is critical in deciding whether a profoundly deaf child with cochlear nerve deficiency (CND) will be suitable for a cochlear or auditory brainstem implant (ABI). Magnetic resonance imaging (MRI) using submillimetric T2 weighted gradient echo or turbo spin echo sequences is mandatory for all profoundly deaf children to diagnose CND. Evidence of audition on behavioural or electrophysiological tests following both auditory and electrical stimulation sometimes allows identification of significant auditory tissue not visible on MRI. In particular electric auditory brainstem response (EABR) testing may allow some quantification of auditory tissue and help decide whether a cochlear implant will be beneficial. Age and cognitive development are the most critical factors in determining ABI benefit.Hearing outcomes from both cochlear implants and ABIs are variable and likely to be limited in children with CND. A proportion of children will get no benefit. Usually the implants would be expected to provide recognition of environmental sounds and understanding of simple phonetics. Most children will not develop normal speech and they will often need to learn to communicate with sign language.The ABI involves a major neurosurgical procedure and at present the long term outcomes are unknown. It is therefore essential that parents who are considering this intervention have plenty of time to consider all aspects and the opportunity for in depth discussion.

Direct Monitoring of ABIs Evoked Potentials on the Cochlear Nuclei and Neighboring Cranial Nerves

Objectives: The potentials evoked with Auditory Brainstem Implant (ABI) on the cochlear nuclei (CN) and on the neighboring cranial nerves are traditionally evaluated with Electrical Auditory Brainstem Response (E-ABR) and electromyography (EMG). To obtain a more precise evaluation of ABI insertion, a near field monitoring procedure that records electrical compound action potentials (E-CNAPs) directly from the CN and from each individual cranial nerve is presented. Methods: Between January 1997 and September 2012, 184 patients were fitted with ABI by the Verona team, 155 in Verona and 29 (13 children and 16 adults) elsewhere. The E-CNAPs utilizes a cotton-wick recording electrode locate on different anatomical structures: CN, root entry zone of the cranial nerve VII, IX, X, XI, and V. All subjects were monitored with E-ABR and 18 of them underwent also E-CNAPs recording. Results: Systematic significant lower E-CNAPs thresholds were observed compared with E-ABRs. The evaluation of the threshold for inducing extra-auditory effects with E-CNAPs on the neighboring cranial nerves allowed a more precise selection of the active electrodes to be used in the fitting. For the same electrical intensity value utilized for obtaining ABI responses, E-ABRs and E-CNAPs showed potentials of neighboring cranial nerves respectively on 4 and 10 electrodes. Conclusions: The adoption of near-field recordings offered the chance to improve the correct placement of the array and post-operative outcomes. E-CNAPs recorded on neighboring cranial nerves can replace EMG giving an on line demonstration of the effects on nerves on which electrodes induce myogenic responses.

Auditory neuropathy spectrum disorder: predictive value of radiologic studies and electrophysiologic tests on cochlear implant outcomes and its radiologic classification

Conclusion: The width of the bony cochlear nerve canal (BCNC) and the size of the cochlear nerve are reliable predictors of long-term speech perception abilities for children with auditory neuropathy spectrum disorder (ANSD) after cochlear implantation (CI). In addition, electrical stapedial reflex (ESR) and electrical compound action potential (ECAP) also have considerable value in predicting postoperative speech perception abilities in these children. Objectives: To assess whether speech perception abilities after CI in children with ANSD can be predicted from the results of radiologic studies and electrophysiologic tests. Methods: Fifteen children with ANSD underwent CI. The width of the BCNC and the size of the cochlear nerve were measured using preoperative CT and MRI. The results of early postoperative ESR, ECAP, and implant evoked electrical auditory brainstem response were reviewed. The latest speech perception test scores were also reviewed. Results: Radiologic findings of normal BCNC and normal cochlear nerve correlated with excellent speech perception abilities after CI. A narrow or obliterated BCNC and a deficient cochlear nerve correlated with poor speech perception abilities. Children with good speech perception abilities showed robust responses on ESR and ECAP, but there were no responses from any of the children with poor speech perception abilities.

Systematic Review of Outcome of Cochlear Implantation in Superficial Siderosis

Superficial siderosis is a progressive disease of the central nervous system associated with chronic subarachnoid hemorrhage. Sensorineural hearing loss occurs early in the disease typically progressing to a profound hearing loss during several years and ultimately affecting 95% of patients. There are published reports of variable outcomes regarding auditory performance for cochlear implantation in cases of superficial siderosis: the objective of this article was to systematically review this evidence. A systematic search of NHS Evidence electronic journal databases AMED (1985 to present), BNI (1985 to present), CINAHL (1981 to present), EMBASE (1980 to present), HEALTH BUSINESS ELITE, HMIC, MEDLINE (1950 to present), and PsycINFO (1806 to present) was performed. Further research using personal communication, Google Scholar, hand searching Otology & Neurotology (2008-2011), and assessment of reference lists identified in other relevant articles yielded additional articles. A total of 24 articles were short-listed based on relevance; no studies were excluded on a basis of quality. Of these 24 articles, 11 were excluded. The 13 articles included in this review report 15 cases of cochlear implantation in superficial siderosis. Of these 15 individual cases, 7 (47%) showed clear sustained benefit from cochlear implantation, 6 showed limited/no benefit from the onset, and the remaining 2 patients' initial benefit was not maintained. Outcomes will depend on the site of lesion and the degree of cochlear nerve functionality, as well as ongoing neural deterioration. Comprehensive assessment of the auditory pathway including electrical auditory brainstem response and magnetic resonance imaging as well as pre/postimplantation counseling is indicated, but these preoperative measures are imperfect predictors of outcomes. There are indications that, where the underlying disease is stable, cochlear implant performance may be sustained, and where there is disease progression (specifically regarding involvement of auditory brainstem nuclei), cochlear implant performance may deteriorate. Further data are needed in this regard; however, results suggest that earlier implantation would provide benefit for a longer period and increase cost-effectiveness.

Cochlear implantation in children with cochlear aplasia

Conclusion: Children with cochlear aplasia can achieve favorable speech perception abilities from cochlear implantation (CI) by inserting an electrode array into the vestibule if an audiological response is reliably demonstrated before surgery by behavioral audiometry and objective measures. Objectives: The purpose of this study was to evaluate the surgical outcome of CI in children with cochlear aplasia. Methods: The medical records of 454 children who underwent CI at the Dong-A University Hospital between January 1994 and September 2011 were reviewed. The prevalence of cochlear aplasia and the preoperative evaluations, operative findings, and postoperative speech perception abilities of implanted children with cochlear aplasia were evaluated. Results: The implanted children with cochlear aplasia accounted for 2% of those with inner ear malformations and 0.4% of all pediatric cochlear implantees. They showed audiological responses in preoperative electrophysiologic tests, and the eighth nerve was present in magnetic resonance imaging. The electrode array was inserted into the vestibule through an oval window after removing the stapes or through a transmastoid labyrinthotomy site. Electrical compound action potential and electrical auditory brainstem response tests showed clear neural responses after implantation. The hearing thresholds of the implanted ear improved to 25 dB HL and the children achieved significant open set speech perception abilities.