Advances in developing new atraumatic concepts of electrode design as well as in the surgical technique have enabled hearing preservation after cochlear implantation surgery, and EAS (electric acoustic stimulation) accompanied with hearing preservation is a new trend for patients with residual hearing at the lower frequencies. Combined post-operative imaging with the referential tonotopic map clearly indicated that hearing preservation can be achieved even in the presence of a long electrode covering the residual hearing region. Achievement of atraumaticity of round window insertion in the present cases has been confirmed from the viewpoint of minimal drilling time as well as preserved vestibular function. Post-operative evaluation after full insertion of the electrodes showed hearing at low frequencies was well preserved in all 16 cases (16 ears) who were followed up for more than one month. As for outcome of EAS, together with successful hearing preservation, all patients obtained 25-40dB in their average hearing threshold after implantation. The word recognition score significantly improved post-operatively. With regard to the genetic background of the patients, CDH23 mutations and the 1555A>G mitochondrial mutation were identified among our series of EAS patients, confirming that these genes were the important genes responsible for high frequency involved hearing loss. Successful hearing preservation as well as good outcomes from EAS in these patients indicated that those with this combination of mutations are good candidates for EAS.

View full abstract

Objective: The audiometric criteria for electric acoustic stimulation (EAS) is now universally defined in the USA and European countries as a mild to moderate low frequency sensorineural hearing loss (within 60–65 dB at 125, 250, and 500 Hz) sloping to a profound hearing loss in the higher frequencies. However, Japanese language is thought to have more importance in the lower frequency range compared to English. We therefore investigated whether the audiometric threshold criteria should be changed or not according to language specifications.
Methods: We designed a comprehension test of Japanese and English using experimentally designed deaf filters with residual hearing in the low frequencies. The test sentences were on a CD, which was played to the subjects at 60 dB SPL in the free field via four designed deaf filters in the lower frequencies. The scores of CID sentence scores (English) and CI-2004 (Japanese) were assessed. There were 8 normal hearing subjects who were bilingual in Japanese and American English. Both test sentences were given to the same subjects consecutively.
Results: The speech comprehension scores were much better in Japanese CI-2004 compared with in English CID. The data from the two groups were statistically analyzed using the paired t-test and the result showed that the mean scores were significantly different (p<0.01 or 0.005) using filters 1, 2, and 3. The distribution of scores was also much wider in Japanese CI-2004.
Conclusion: Japanese language contains more vowels and gliding consonant sounds (=semivowels) in sentences and has more importance in the lower frequency range compared to English. In addition, the personal equation in Japanese sentence recognition is also larger. Therefore, the audiometric threshold criteria should be changed and the proper guidelines including not only a monosyllabic test but a sentence comprehension test should be added according to the language specifications for EAS cochlear implantation.

View full abstract

Electroacoustic stimulation (EAS) for partial deafness with preserved low-frequency hearing is proving as an emerging alternative for these patients who cannot be aided conventionally. Cochlear implantation for EAS requires different reasoning and alterations to conventional cochlear implantation strategies with regard to patient selection, preservation of residual hearing and rehabilitation. We want to share our experiences with our EAS cases and in context of the current literature. The short to longterm outcomes of hearing preservation and performance will be presented and factors perceived to be crucial for successful outcomes elaborated. Key factors in hearing preservation will be discussed and methods of improvement proposed.

View full abstract

As a new application of neural prostheses for deafness, electrical stimulation from a cochlear implant is used to complement residual low-frequency hearing. When hearing is preserved, the combination of acoustic hearing in low frequencies and electrical stimulation of high frequencies can lead to very high levels of speech understanding, especially in a noise environment. The combination of electric and acoustic hearing is termed electric acoustic stimulation (EAS). On the other hand there is a very real risk that patients implanted with the cochlear implant may lose a substantial proportion of their residual acoustic hearing at low frequencies. Preservation of the residual hearing is assumed to be influenced by two factors, i.e., the intracochlear trauma caused by insertion of an electrode of a cochlear implant and the change in the dynamics of the basilar membrane (BM).
In this study, to clarify the influence of the electrode inserted into the cochlea on the dynamic behavior of the BM, a three-dimensional finite-element model of the human cochlea was created. The traveling wave of the BM caused by the vibration of the stapes was analyzed considering a fluid-structure interaction with the cochlear fluid. Next, the influence of the electrode on the vibration of the BM was examined by inserting the electrode model into the scala tympani of the cochlear model. In order to investigate the effect of the insertion method, the length and position of the electrode and the stiffness of the round window membrane (RWM) were changed.
When the electrode was inserted into the cochlea, the amplitude of the BM was suppressed by 10 dB or less at low frequencies compared to the intact cochlea. However, if ossification of the RW was induced (e.g., by using the RW approach), the vibration of the BM was suppressed by 20–40 dB. The degree of the suppression depended on the length and position of the electrode. The characteristic frequency (CF) of the BM in the apex area shifted to the low frequency side if the electrode was located adjacent to the BM.
Our computer model analysis showed the cochleostomy approach offers a greater advantage for hearing preservation, because the RWM may become very stiff following electrode insertion via the RW approach.

View full abstract

First, we compared cortical activation by speech in postlingually deafened cochlear implant (CI) users with that in normal hearing subjects using positron emission tomography (PET). Increased activation was observed in CI users not only in the temporal cortices but also in Broca’s area and its right hemisphere homologue, supplementary motor area (SMA) and anterior cingulate gyrus. These regions are thought to be establishing working memory for language decoding and encoding, enabling the brain to maintain an internal copy of the original auditory message, which might be activated more in CI users than in normal subjects. Next, we used 18F-fluorodeoxyglucose (FDG)-PET to measure the cortical glucose metabolism in profoundly deaf children with visual language stimuli and observed significantly higher cortical ­metabolism in the pre-central gyrus, middle temporal gyrus in the right hemisphere, and superior ­temporal gyrus and superior parietal lobule. Individual analysis revealed a strong cortical activation in a child who was the worst user of spoken language, while there was no significant increase in the overall cortical metabolism in the child who was the best user of spoken language. Our recent study also revealed a correlation between the functional reorganization pattern of language networks and the genetic cause of deafness in profoundly deaf individuals. Our results confirmed that the temporal auditory cortices of deaf children develop to process visual aspects of language if they do not receive sufficient auditory ­signals and depends on visual cues. FDG-PET with a visual language task provided objective information on the development and plasticity of cortical language networks. Functional brain imaging may be of help for both the parents of hearing-impaired children and the professionals involved in their habilitation and education decide upon the appropriate mode of communication for each child.

View full abstract

Cochlear implantation (CI) combined with residual hearing preservation is a fascinating concept which is possible due to recent improvements in surgical technique and advanced electrode design. Current candidacy includes adults and children with significant residual hearing. Residual hearing must be maximally protected during cochlear implantation, since preservation of cochlear sensorineural structures contribute to a better outcome with electrical stimulation. Further pharmacological therapies for paediatric patients also necessitate maximum functionality of intracochlear structures to be effective. Results obtained in several implantation centres over the world with soft, standard size Med-El electrodes demonstrate that full electrode insertion (around 28 mm) is possible without compromising residual hearing. Such an approach provides the benefit of complete cochlear coverage for electrical stimulation combined with low-frequency acoustic hearing. The use of such soft electrodes in atraumatic surgery can therefore improve sound perception in difficult hearing conditions.

View full abstract

Background: An atraumatic insertion is one of the conditions to succeed to preserve low frequencies in case of electro acoustic stimulation. Preservative procedures are also important to preserve vestibular functions, particularly in very young children, and in case of bilateral implantation. Atraumaticity requires a specific surgical procedure, and a specific electrode array. Many publications reported high rates of hearing preservation with short electrodes. Nevertheless, many evidences argue for potential benefits of using cochlear implant electrodes that extend into the apical regions of the cochlea. A complete coverage provides additional low-pitched auditory percepts and thereby increases the spectral information. Apical electrodes are able to selectively stimulate discrete and tonotopically ordered neural populations near the apex of the spiral ganglion. In this area, neuronal tissue (ganglion cells) is dense. Intracochlear potentials recordings showed that this area is very reactive and clinical evaluation demonstrated patient’s preferences to complete cochlear coverage.
Medel developed a long atraumatic electrode (flex soft) and the aim of this study is to evaluate the hearing preservation with this electrode and the benefit of the bimodal stimulation.
Materials and methods: this multicentric study (Rennes, Bordeaux, Paris, Lyon) included 12 patients who were implanted with Medel Sonata Ti100, electrode 31,3 mm flex soft. The low frequencies were preserved in all these patients and a speech processor EAS DUET was applied for electroacoustic stimulation. Patients were tested in different situations: acoustic only, electric only, and bimodal electroacoustic.
Results: There was a significant advantage for the EAS condition in speech recognition in quiet situation and in noise. Questionnaires exhibited patients’ preferences for the EAS condition.
Conclusion: preservation of inner ear functions is possible with a long electrode with a specific surgical procedure and an atraumatic electrode array. Providing information from low frequencies increases auditory performances.

View full abstract

A novel therapeutic method for sensorineural hearing loss using a newly-invented auditory device is explored. This new auditory device is designed to be implanted into the cochlea, converting the vibratory movements of the basilar membrane to electrical signals, and stimulate spiral ganglion neurons by a piezoelectric effect. Two prototype models, different in size, have been fabricated to examine the theoretical validity of the novel device. A primary prototype device, 3 cm in length, was manufactured to examine the response of a piezoelectric sheet to sound vibration. It was demonstrated that a trapezoid-shaped piezoelectric sheet was able to generate electrical signals in response to sound vibration with frequency characteristics, and to stimulate spiral ganglion neurons using the generated signals in a guinea pig. A secondary prototype device, an implantable device 1 mm in length, was made to test the possibility of sound vibration, applied from the external auditory canal of a guinea pig, to be transmitted to a piezoelectric sheet inserted into the cochlea via the ossicular chain and the basilar membrane. Using a laser Doppler vibrometer, vibration of the piezoelectric membrane was detected when sound was applied through the external auditory canal. These results indicate that the new auditory device, mimicking the function of cochlear hair cells, is a promising tool for restoration of the auditory function.

View full abstract

The Vibrant Soundbridge (VSB) is an active middle ear implant designed to “directly” drive the ossicular chain for the treatment of hearing loss. Although initially intended and applied for sensorineural hearing loss, the VSB has recently been applied to conductive and mixed hearing losses as well. The aim of this paper is to evaluate the aided benefit from different surgical options and to consider medical and surgical complications.
The VSB was implanted in adults with conductive or mixed hearing losses using the round window approach (Round Window (RW) Vibroplasty), or in combination with a PORP, TORP or Stapes prosthesis. The new couplers further expand treatment options for attaching the FMT to remnants of the ossicular chain. In ears with chronic mastoid cavities, reconstruction of the canal wall with cartilage has been useful.
Surgery for atresia cases with major malformations of the outer and middle ear involves aesthetic as well as functional aspects. Reconstruction of the auricle is well established and has shown favorable results, whereas restoration of the middle ear sound conduction mechanism was considered possible, but surgically challenging. Unfortunately, functional results have turned out to be limited: for approximately 50% of the patients, hearing results with conventional techniques are unsatisfactory and a hearing aid is necessary. The VSB offers new possibilities for atresia cases, allowing for individual solutions for fixing the FMT. Several options have been explored, such as modifying the original clip so that an upside–down fixation to a malformed stapes superstructure was possible, or using the couplers or RW application.

View full abstract

The classic indication for the use of the Vibrant Soundbridge (VSB) is sensorineural hearing loss and a floating mass transducer (FMT) with a titanium clip is crimped to the long process of the incus. In 2006, Colletti et al. were the first to describe the application of the VSB on the round window, which they called a vibroplasty, and which is emerging as a versatile solution for various causes of conductive or mixed hearing loss. The objective of this study was to present the frequency of candidacy with middle ear diseases for VSB in Japanese patients with mixed hearing loss.
We searched our database for all patients receiving conventional otosurgical procedures within a period from September 2004 to November 2008 at Shinshu University Hospital. We selected 230 patients and all patients who were younger than 18 years of age and who had a history of previous otologic surgery for tumors or perilymphatic fistulae were excluded from this study. Consequently, 112 patients were evaluated.
The mixed hearing loss was postoperatively found to be in 35% in chronic otitis media, 27% in cholesteatoma and 9% in otosclerosis patients. Bilateral involvement was present in 26%. Nine patients (8%) with bilateral moderate to severe mixed hearing loss needed to wear a hearing aid, but 7 of the 9 patients (6%) could not use a hearing aid for medial reasons.
Tympanosclerosis was identified in 8 of 9 patients (89%) who had bilateral middle to severe mixed hearing loss in the present study. The VSB might be indicated in some patients with tympanosclerosis, but we think that round window vibroplasty should be indicated for the patients with round window otosclerosis. We have speculated that the candidates for vibroplasty with VSB in the treatment of middle ear disease would amount to an average of 1.5 patients per year at each hospital which regularly performs conventional otosurgery.

View full abstract

These last years, different papers have demonstrated good surgical and audiological results in patients with conductive and mixed hearing losses, when the FMT is placed on the round window, on the stapes or on the incus. We present the preliminary results of a prospective multicenter French study comparing the results of the VSB in mixed hearing loss with BAHA and conventional hearing aids.
Materials and methods: 30 patients whose pathologies were mainly chronic otitis (22 cases) and otosclerosis (8 cases) were implanted with a VSB middle ear implant. The surgical approaches used consisted in the classical approach (FMT on long process of the incus) in 8 cases, in placement of the FMT on the stapes in 12 cases, and in placement of the FMT on the round window in 10 cases. Thresholds in air conduction, bone conduction, speech understanding and speech understanding in noise were measured at 1, 3, 6, and 12 months, and compared with preoperative measurements with numeric conventional hearing aid and head set BAHA
Results: No surgical complications were reported. 4 patients expressed a lack of hearing improvement and the FMTs were replaced under local anesthesia. In these four cases, the FMT had been placed on the round window. There were no change in bone conduction hearing thresholds and all patients are showing significant gain with VSB and improvement 17 dB below the air conduction thresholds in average. In average, speech understanding was better for VSB than BAHA and hearing aids. Results in speech understanding were identical between VSB and BAHA for pure conductive heanring loss, and were better for VSB than BAHA when the bone conduction thresholds were higher than 40 dB.
Conclusion: Preliminaty results have shown that the VSB middle ear implant can be a good alternative for the rehabilitation of mixed hearing losses.

View full abstract

We present case details of the round window (RW) application of the Vibrant Soundbridge^® (VSB) experienced in Japan from 2006 to 2011. So far, four cases have been experienced in Japan; two at Osaka University, one at Nagasaki university, and the remaining one at Shinshu University (Matsumoto). The four patients consisted of two men and two women with ages ranging from 60 to 71 years, all of whom had histories of having various types of chronic otitis media with moderate to severe mixed-type hearing losses, which were not improved by surgical procedures or were not expected to improve due to possible severe sclerotic lesions in the middle ear. One of the two Osaka cases had a bone-anchored hearing aid (BAHA) on the opposite ear. The transmeatal approach and facial recess approach were used in two Osaka cases and in the Matsumoto case, respectively, whereas the floating mass transducer was introduced into the RW niche via the epitympanum in the Nagasaki case , as there was a radical cavity in that patient’s ear. The postoperative course in all four patients was uneventful, and to date we have obtained good results in pure-tone hearing as well as language perception in all patients. Pure-tone thresholds improved 50 and 60 dB on average in the two Osaka cases, respectively, and the level, by which word perception attained 80–90%, had improved by about 30 dB in one of the Osaka cases. Word perception improved to a level similar to that by BAHA in the opposite ear in the other Osaka case. Although improvement in the pure-tone threshold was 25 dB on average, the word perception in the Nagasaki case significantly improved after surgery for silence as well as in noise. In the Matsumoto case, the improvement in the pure-tone threshold was 26.7 dB on average, and that of speech recognition in the free field was 65% for 50dB, 55% for 60dB, and 10% for 70dB in the quiet.

View full abstract

We have undertaken pediatric bilateral cochlear implantation (PBCI) in 29 (17%) of 169 children who were receiving Auditory-Verbal/Oral therapy at our cochlear implant center. We report herein on the effectiveness of PBCI based on our experience, patients’ background, their/their parents’ hope, guidance and counseling about a second CI, mapping technique and instructions for stabilization about, and daily hearing after, the second CI.
The clinical effects with binaural hearing are well known as binaural summation, the head shadow effect, binaural squelch, and there is strong evidence for a better hearing performance under noise. Our experience was in accord with the previous results and PBCI shows a large degree of effectiveness in a classroom environment such as a school or kindergarten.

View full abstract

One of the problems in considering the indication for cochlear implantation (CI) is the lack of a reliable retrocochlear function test when cochlear loss is combined with retrocochlear diseases. We have used a promontory and/or an extratympanic electrical stimulation test (EST) as an exclusion criterion for such candidates with a complete absence of auditory perception at any stimulation levels. The side for CI surgery could be thus decided in case where a nonresponsive ear was found on one side. Bilateral abnormal EST responses, such as “adaptation”, were found in adult auditory neuropathy patients whose performances with CI were suboptimal. Bilateral absence of the EST response was found in a patient with superficial siderosis. On the other hand, we have experienced a patient with hypertrophic pachymeningitis, who showed distinct responses both to preoperativeEST and to electric stimuli during mapping but no speech perception at all with the activated implant. It is concluded that a positive EST may be a necessary condition for open-set speech recognition but still be insufficient to indicate that a given patient will have an optimal performance with CI.

View full abstract

Assessment of Language Development for Japanese Children: ALADJIN, was conducted by the Research on Sensory and Communicative Disorders (RSCD) project, a nationwide research project sponsored by Ministry of Health, Labor and Welfare. The RSCD project was originally developed to assess the effectiveness of interventional methods for hearing-impaired children, and ALADJIN was originally used for this aim. The contents and the aim of this test are discussed herein.

View full abstract