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Objective: Implantable hearing aids present a new treatment modality for patients suffering from sensorineural hearing loss. The functional gain obtained with the partially implantable Symphonix soundbridge system was evaluated in a clinical study. The audiological results achieved with n = 34 patients over a period of up to three years are presented in this second part of the publication., Patients and Methods: 34 patients have received the Symphonix Vibrant soundbridge system since February 1997. The average age at implantation was 47.2 years (minimum: 18.9 years; maximum: 80.3 years). All patients have had several years of experience with hearing aids, which, however, provided insufficient functional gain or could not be fitted with a conventional hearing aid for medical reasons (such as auditory ear canal problems). All patients fulfilled the audiological selection criteria as they had bilateral moderate to severe sensorineural hearing loss. As a rule, the ear with poorer performance was implanted. All patients were fitted with the audio processor eight weeks after the implantation. The pure tone thresholds, the functional gain, the monosyllable and sentence understanding (Göttinger Sentence Test in quiet and noise) were preoperatively and postoperatively assessed. Standardized self-assessment questionnaires were used to evaluate the subjective benefit (PHAB) and the quality of hearing (HDSS) as compared to the preoperative situation. Further hearing tests were performed after four weeks, three, six, nine, twelve, eighteen, twenty-four and thirty-six months postoperatively. During the observation period of up to three years the audioprocessor was updated several times, most recently with the fully digital three-channel-system Vibrant D. The results obtained were documented., Results: Postoperatively, the pure tone threshold with the soundbridge system switched off did not change significantly in the implanted ear. All patients had a functional gain that was either comparable to the gain achieved with hearing aids or better. In particular speech-related frequencies showed improved amplification. The free field speech recognition tests revealed higher scores in quiet and in noise. The patients commended the natural sound quality, the lack of feedback, the absence of occlusion and distortion, the improved speech understanding in noise and the favourable cosmetic appeal. Only two patients failed to achieve better results as compared to their performance with conventional hearing aids. No complications, such as a deterioration of hearing due to inner ear damage or a conductive hearing loss, were observed in the long-term., Conclusions: The Symphonix Vibrant Soundbridge is a new and promising treatment modality for patients suffering from moderate to severe sensorineural hearing loss. Further improvement of the good results can be expected with improved coupling of the transducer to the ossicular chain and further development of signal processing.

The Vibrant Soundbridge, a semi-implantable hearing device for subjects with moderate to severe sensorineural hearing impairment was introduced commercially. First audiologic results are presented on 63 patients from 10 European implant centers. Hearing loss was at 0.5, 1, 2, and 4 kHz varying between 43 and 81 dB HL. The patients used the analogue audio processor, type 302. Measured sound-field gain was compared with NAL-R target values. For most patients an acceptable agreement was found. There was a subgroup of patients, however, with relatively low gain. The results suggest that this was related to the suboptimal positioning and fixation of the transducer to the incus.

Objective: This study aimed to determine the maximum dose of radiation the CLARION 1.2 cochlear implant can withstand safely., Introduction: Cochlear implants restore functional hearing to patients with sensorineural deafness. Because some patients may need radiation therapy, it is important to investigate the influence of ionizing radiation on cochlear implant function., Methods: This study tested the function of four CLARION 1.2 implants (Advanced Bionics, Sylmar, CA, U.S.A.) after varying radiation treatments with gamma rays. The first implant received a cumulative dosage of 69 Gy over nine treatments (single doses between 0.1-30 Gy). The second was irradiated with a total of 90 Gy, receiving three treatments of 30 Gy each. The third and fourth received doses more typical of patient therapy (i.e., 2 Gy) approximately 30 times, for a cumulative dosage of approximately 60 Gy. Implant function was tested after every treatment; the CLARION implant incorporates a back-telemetry system, allowing impedance and current output testing., Results: Despite the type of treatment, the results were quite consistent: difficulties in function occurred when the cumulative dosage inside the implant was approximately 60 Gy. The first implant recovered completely and the second recovered partially., Discussion: The CLARION 1.2 cochlear implant seems to safely withstand approximately 60 Gy of radiation before experiencing functional difficulties. In a clinical situation, the implant would not likely be in the target volume irradiated, and thus the patient's therapeutic cumulative dosage might be higher.

Introduction: Patients suffering from moderate to severe cochlear hearing impairment can not be considered for cochlear implantation on account of their relatively good residual hearing. Conventional hearing aids, on the other hand, have considerable disadvantages which clearly limit the benefit for these patients, e.g. feedback, sound distortion, unfavorable conditions for frequency transfer, occlusion, and recurrent infections of the auditory canal. In addition, many patients complain about a poor speech intelligibility in noise. VIBRANT SOUNDBRIDGE HEARING PROSTHESIS: Implantable hearing aids offer a new approach for improved auditory rehabilitation. The Vibrant Soundbridge system is based on an electromagnetic system, which is linked directly to the intact ossicular chain. Due to the high sound quality and the high frequency characteristic this system is ideally suited for the above-mentioned patient group. The usual disadvantages of conventional hearing aids can be avoided. Externally visible is merely the audio processor, which is worn in the retroauricular area and covered by hair. This processor transfers data and power via magnetic attachment transcutaneously. PATIENT POOL: During a European multicenter clinical study, 19 patients were implanted at MHH since February 1997. No significant complications occurred., Results: In all patients, postoperative unaided pure tone threshold was unaltered in comparison with the preoperative recordings. The use of the audio processor leads to a significant functional gain, particularly in the high frequencies. The patients report about undistorted hearing resulting in a better speech understanding even in situations with loud background noise., Conclusion: The preliminary results show a promising new approach to the use of hearing prostheses for patients suffering from moderate to severe sensorineural hearing loss.

The prospective, matched-pair study comparing users of the Clarion system and the Nucleus system seems to indicate that the patients using the Clarion system are obtaining open-set speech understanding at a faster rate than Nucleus patients. The sample size in this study is very small at present, but with increasing numbers of Clarion patients, we will carry on with this study. Further, it remains to be seen whether or not the observed advantage will continue for the Clarion users in the longer term.

Our experience with deaf adults and children who have received the Clarion multistrategy implant are very encouraging. Because of certain programming characteristics of the current device, access to the compressed analog coding strategy has been limited. We expect to see this change in the near future. The CIS strategy, however, appears to provide patients with important, full-spectrum speech information so that they accommodate to the auditory sensations rapidly and begin to interpret sound into meaningful speech within a short time.

Evaluation of the intraoperative electrically evoked stapedius reflexes during cochlear implant surgery has two purposes: (1) The functioning of the device and the peripheral auditory pathways can be proven immediately and (2) The data of reflex threshold can be used for the prediction of later threshold (T)- and maximum comfortable (C) levels. This is especially useful for the later fitting of the speech processor in very young children. When trying to use the stapedius reflex data for the prediction of T- and C-levels it must be considered that during surgery the drugs used for general anaesthesia influence the values of the stapedius reflex. Depending on the drug, the stapedius reflex threshold can be increased or the reflex can even be totally blocked. This is not only due to relaxants but also to anaesthetics. To investigate this influence we first determined the acoustically evoked stapedius reflex threshold in normal hearing adults under general anaesthesia with 7 different anaesthetics without additional relaxation. It was found that especially with Dormicum and Brevimytal the stapedius threshold increased only very lightly or did not change at all. In a second investigation the electrically evoked stapedius reflex thresholds were obtained in adults who underwent a cochlear implant surgery using the same anaesthetics for anaesthesia. The intraoperatively evaluated reflex data were compared with postoperatively obtained data. It was found that both reflex thresholds were similar if evaluated in Dormicum or Brevimytal anaesthesia. This suggests that only with the use of the right anaesthetics the data of the electrically evoked stapedius reflex obtained intraoperatively can be used for predicting T- and C-levels.

The probability of system failures increases as the number of cochlear implants increases throughout the world. Whether a malfunction is a technical or physiological problem remains to be defined, particularly in very young children, while a psychogenic hearing disorder after implantation must not be excluded in adults. The battery of objective measurements used clinically at the Medizinische Hochschule, Hannover has provided useful diagnostic information for distinguishing possible causes of failure. In a normally functioning device, an electrical signal equivalent to the biphasic rectangular stimulation pulse can be recorded by measuring skin potentials from surface electrodes placed on the mastoid of the implant side and the forehead. The signal from the stimulated implanted electrodes is derived by applying a constant pulse rate. Signal averaging is not necessary. If no signals are observed, a non-functioning device should be suspected. If the device works normally, function of the auditory pathways can be examined by recording the electrically elicited stapedius reflex or electrically evoked brain-stem responses. In our experience with more than 450 cochlear implant patients, eight internal device failures occurred, while an additional three patients had either reduced or no hearing sensations due to a disorder of the auditory pathways.

Electrically elicited stapedius reflex thresholds are an objective criteria for the fitting of speech processors in very young children. Reflex thresholds generally fit well within the upper third of a subject's individual dynamic range, the difference between electrical threshold of hearing, (T) and maximum comfort (C) levels and can be used to predict ultimate behavioral maximum comfort levels. In acoustically elicited stapedius reflexes a saturation of impedance amplitude can be registered at approximately 110 dB, which is 90% of the dynamic range. Assuming a similar relationship for the electrically elicited stapedius reflex there would be two values within the dynamic range which could be used for extrapolation of the threshold level. In the present study, the electrically elicited stapedius reflex was examined in 16 deaf patients who had received 22-channel Clark/NUCLEUS cochlear implants. Using an apical, a medial and a basal electrode pair, different stimulation positions within the cochlea were tested. The contralateral reflexes could be elicited in 11 patients (69%). A saturation of the reflex amplitude was recordable in 10 subjects, at least in one of the electrode pairs. The reflex saturation in all cases was located close to the uncomfortable loudness level within the subjects' dynamic ranges (at 95% dynamic). This finding is comparable to acoustic matter. As a result, these data together with reflex threshold data suggest a means for predicting to predict the threshold levels.