Hamidreza Mojallal

Multicenter Study With a Direct Acoustic Cochlear Implant

Objective To confirm the clinical efficacy and safety of a direct acoustic cochlear implant. Study Design Prospective multicenter study. Setting The study was performed at 3 university hospitals in Europe (Germany, The Netherlands, and Switzerland). Patients Fifteen patients with severe-to-profound mixed hearing loss because of otosclerosis or previous failed stapes surgery. Intervention Implantation with a Codacs direct acoustic cochlear implant investigational device (ID) combined with a stapedotomy with a conventional stapes prosthesis Main Outcome Measures Preoperative and postoperative (3 months after activation of the investigational direct acoustic cochlear implant) audiometric evaluation measuring conventional pure tone and speech audiometry, tympanometry, aided thresholds in sound field and hearing difficulty by the Abbreviated Profile of Hearing Aid Benefit questionnaire. Results The preoperative and postoperative air and bone conduction thresholds did not change significantly by the implantation with the investigational Direct Acoustic Cochlear Implant. The mean sound field thresholds (0.25–8 kHz) improved significantly by 48 dB. The word recognition scores (WRS) at 50, 65, and 80 dB SPL improved significantly by 30.4%, 75%, and 78.2%, respectively, after implantation with the investigational direct acoustic cochlear implant compared with the preoperative unaided condition. The difficulty in hearing, measured by the Abbreviated Profile of Hearing Aid Benefit, decreased by 27% after implantation with the investigational direct acoustic cochlear implant. Conclusion Patients with moderate-to-severe mixed hearing loss because of otosclerosis can benefit substantially using the Codacs investigational device.

Histological evaluation of novel ossicular chain replacement prostheses: an animal study in rabbits

Conclusion. The improved biocompatibility of Bioverit® II coated with a nanostructured surface shows promising qualities for use in human reconstructive middle ear surgery. In the case of chitosan-hydroxyapatite composite prostheses, further investigations regarding composition of the material, degree of purity and design are necessary before clinical application. Objective. The selection of optimal materials for reconstructive middle ear surgery continues to be a problem. In the present study novel materials were tested as total ossicular replacement prostheses (TORPs) in an animal model. Materials and methods. Bioverit® II coated with a nanostructured surface and chitosan-hydroxyapatite composites were placed in the middle ear of 40 rabbits. Uncoated Bioverit® II was used as control. After an implantation period of 28, 84 or 300 days petrous bones were extracted, embedded in epoxy resin and examined by light microscopy. Results. Uncoated and coated Bioverit® prostheses revealed a mucosal coverage and a little osseogenic response after 28 days. The results of the coated Bioverit® prostheses slightly surpassed those of the plain prostheses. Chitosan-hydroxyapatite composite prostheses were mostly found to be dislocated after 28 days. Formations of granulation tissue and fibrotic capsules were observed around these implants. This reaction could be caused by the instability of the composite material or may be due to impurities present in the chitosan.

First clinical experiences with a direct acoustic cochlear stimulator in comparison to preoperative fitted conventional hearing aids.

Objective Patients with moderate-to-severe mixed hearing losses (MHLs) are hard to provide sufficient benefit with currently available conventional hearing aids. Here, the long-term safety of a direct acoustic cochlear stimulator (DACS) and the effectiveness compared with conventional “high-performance” hearing aids were investigated. Study Design Prospective, within patient reference, nonrandomized, interventional multicenter clinical study performed at these 3 centers: Medical University Hannover, University of Heidelberg, and Helios Hospital Krefeld. Patients and Intervention Ten otosclerosis patients with severe-to-profound MHL were preoperatively fitted with state-of-the-art conventional hearing aids (HA). After 2 months of testing conventional HA, 9 of the patients decided to be implanted with a DACS. Main Outcome Measures Air conduction (AC) and bone conduction (BC) aided and unaided thresholds, speech discrimination before and after implantation and at 3, 6, and 12 months after activation. The subjective benefit was assessed by the Abbreviated Profile of Hearing Aid Benefit (APHAB). Results Preoperative hearing thresholds were preserved over the 12 month observation time after activation. Average functional gain (0.5–4 kHz) achieved with conventional HA was 47 dB compared with 56 dB with the DACS. Speech-in-noise tests revealed a lower SNR for DACS (3.1 dB) than for the HA (6.6 dB) and patients were more satisfied with the DACS. Conclusion The DACS significantly improved hearing, speech intelligibility, and satisfaction in patients with a severe-to-profound mixed hearing loss and can be considered a safe and useful alternative to conventional hearing aids.

Power stapes: an alternative method for treating hearing loss in osteogenesis imperfecta?

Objective: To present power stapes, stapedotomy, and middle ear implantation with Vibrant SoundBridge (VSB) performed in a one-step surgery as an alternative option for hearing rehabilitation in patients with osteogenesis imperfecta (OI). Study Design: Retrospective case series. Setting: Tertiary referral ear center. Patients: A family with genetically proven OI Type I. Interventions: Two patients, mother and son, with severe to profound mixed hearing loss underwent 3 power stapes, 1 unilateral and 1 bilateral sequential. Main Outcome Measures: Thorough audiological diagnostic batteries including aided and unaided pure-tone and free-field audiometry and Freiburg monosyllabic word test were used to assess the preoperative status and the postoperative hearing outcome. High-resolution computed tomography of the temporal bones was performed as well. Surgical procedure and any special considerations were analyzed in detail. Results: The hearing outcome was favorable in all cases, showing in comparison to the preoperative values an average improvement of 36.8 dB. Severe intraoperative bleeding of the middle ear mucosa was the only complication and could be easily controlled by allowing short time intervals. Inner ear trauma did not occur in any case. Conclusion: Power stapes represents a safe and promising procedure for treating hearing loss in selected patients with OI. Furthermore, it introduces a new, advantageous VSB application in cases of mixed hearing loss with severe otosclerosis and increased bone-conduction thresholds.

Retrospective audiological analysis of bone conduction versus round window vibratory stimulation in patients with mixed hearing loss

Abstract Objective: To compare audiological outcomes in mild-to-moderate mixed hearing loss patients treated with a bone-anchored hearing aid or an active middle-ear implant. Analysis aimed to refine criteria used in preoperative selection of implant type. Design: Retrospective comparative analysis of audiological data. Follow-up time ranged between 0.55 and 8.8 years. Study sample: For detailed comparative analysis, 12 patients (six in each group) with comparable bone conduction thresholds and similar clinical characteristics were selected. A larger cohort of 48 patient files were used to evaluate overall audiological indication criteria (24 per group). Results: In free-field tone audiometry, Baha patients showed mean aided thresholds between 40–48 dB, whereas hearing thresholds for VSB patients were 25–43 dB. Baha and VSB users had mean WRS of 56% and 82%, respectively, at 65 dB. Better speech understanding in noise was seen with the VSB. Conclusion: Analysis of the main cohort (n = 48) showed that treatment with round window vibroplasty leads to better hearing performance than treatment with a bone-anchored hearing device, if the bone conduction pure-tone average (0.5 to 4 kHz) is poorer than 35 dB HL. Audiological analysis in the smaller comparative analysis showed similar findings.

Normative Auditory Brainstem Response Data for Hearing Threshold in the Rabbit

In an experimental study, we determined the physiological hearing threshold of the rabbit in order to use these data as normative values for further experimental investigations. The aim was to use different acoustic stimuli (click and tone-pip stimuli) with different frequency spectra for air and bone conduction (BC) in order to obtain further information about the optimal form of stimulus when recording auditory evoked potentials in the rabbit. For the investigation, we used 46 female New Zealand rabbits weighing 3.2–4.4 kg and aged 6 months. The equipment used to record brainstem auditory evoked potentials was the Nicolet Viking IV P System (Nicolet Biomedical, Inc.). In accordance with the experimental set-up, the measurements took place under intubation anesthesia, with a total of four repeat measurements performed on each ear at different times. Tone-pip and click stimuli with varying intensities of stimulus, transmitted via air conduction and BC, were applied. The I-IV waves proved the most stable for both stimulus modalities. They were registrable in 98.7% of cases, whereas only 30.2% of the V waves could be recorded. Values averaged from all measurements made throughout the study yielded a potential threshold of 34.8 dB peak equivalent (p.e.) SPL for the click stimulus, 13.8 dB p.e. SPL for the tone-pip stimulus at 8 kHz and 34.2 dB p.e. SPL for the click stimulus transmitted via BC. With regard to latencies, the results indicated a good reproducibility through different stimuli with acceptable standard deviations. The values for physiological hearing threshold obtained here can serve as normative data in subsequent experimental animal studies.

A biomechanical ear model to evaluate middle-ear reconstruction

Abstract In order to evaluate the efficiency of middle-ear prostheses in near-real conditions, an artificial model was developed that approximately simulates the actual geometrical and biomechanical properties of the ear system (excluding the ossicular chain). The sound transmission characteristics of selected commercial middle-ear prostheses and of a synthetic test material were measured using laser Doppler vibrometry (LDV) in this model. The models realistic properties enabled clinical tympanometry to be used to control the stiffness. In addition the influences of the implant mass on transmission characteristics were investigated. With an averaged displacement between 10 and 100 nm/Pa up to 2000 Hz, the transmission characteristic of the model was comparable with data obtained from the intact middle ear in temporal bone experiments. From the acoustical point of view, no significant material-specific differences could be found. Increasing the mass of the implants to more than 50 mg results in poorer acoustic transmission. In general, changes to the stiffness involving compliance values greater than 3.5 ml and smaller than 0.2 ml led to poorer acoustic transmission. Sumario Con objeto de evaluar la eficiencia de las prótesis de oído medio en condiciones cercanas a la realidad, se desarrolló un modelo artificial que simula de manera aproximada las propiedades geométricas y biomecánicas reales del sistema auditivo (excluyendo la cadena oscicular). Se midieron las características de transmisión del sonido de prótesis comerciales seleccionadas de oído medio y de un material de prueba sintético, usando vibrometría laser Doppler (LDV) en este modelo. Las propiedades realistas del modelo permiti-eron el uso de la timpanometría clínica para controlar la rigi-dez. Además, se investigaron las influencias de la masa del implante en las características de transmisión. Con un despla-zamiento promedio entre 10 y 100 nm/Pa, hasta 2000 Hz, la característica de transmisión del modelo fue comparable con los datos obtenidos de un oído medio intacto en experimen-tos en hueso temporal. Desde el punto de vista acústico, no se pudieron encontrar diferencias significativas relacionadas específicamente con el material. El incremento de la masa de los implantes a más de 50 mg, determina un empobrec-imiento de la transmisión acústica. En general, los cambios en la rigidez involucran valores de compliancia mayores a 3.5 ml y menores de 0.2 ml, que llevan a una transmisión acústica más pobre.

Normative data of multifrequency tympanometry in rabbits

In an experimental study, we evaluated acoustic immittance in rabbits in order to use these data as normative values for further experimental investigations. This study is the first experimental evaluation of both conventional 226 Hz and multifrequency tympanometry (MFT) in rabbits. For the investigation, we used 33 female New Zealand rabbits weighing 3.2–4.4 kg and aged six months. Bilateral measurements using conventional 226 Hz and MFT were performed under general anaesthetic. A 226 Hz tympanogram was recorded for all animals by conducting an air pressure sweep from +200 to −400 daPa at a rate of 50 daPa/s. Subsequent tympanograms were recorded over a wide frequency range from 250 to 2000 Hz. The acoustic impedance device used in this study provided reproducible and evaluable tympanograms. The applied tone frequency of 226 Hz proved to be especially suitable for determining compliance. Normative data obtained from our study reveal the resonance frequency to be 1368 ± 205 standard deviation (SD) for the right side and 1413 ± 216 SD for the left side. The values for physiological acoustic immittance of the middle ear in the rabbit obtained here can serve as normative data in subsequent experimental animal studies.

Multifrequency tympanometry: experimental application after implantation of ossicular replacement prosthesis in rabbits.

We used multiple-frequency tympanometry (MFT) to evaluate the influence of a newly developed ossicular replacement prosthesis on transmission characteristics of middle ear. Background: Multiple-frequency tympanometry is a technique for evaluating the emittance of the middle ear over a wide frequency range. It has been shown to be sensitive to certain middle ear conditions that are not detected by conventional 226-Hz tympanometry. In the field of experimental evaluation, MFT has been shown in certain animal studies to be useful in monitoring diseases. Methods: Thirty-six prostheses composed of titanium dioxide ceramic were implanted into the right middle ear of female rabbits. Bilateral measurements using conventional 226-Hz and MFT were performed before implantation and after 28, 84, and 300 days postoperatively. The results of the preoperative examinations yielded reference values for physiological resonance frequency. After dissecting the temporal bone, we opened the middle ear and analyzed both the surrounding tissue and the position of the prosthesis. Results: The constant values for compliance revealed by both preoperative and postoperative measurements indicate good reproducibility of 226-Hz tympanometry. Postoperatively, resonance frequency increased continuously up to the 300th day. The observation supports the assumption that the higher stiffness level of connective tissue influenced resonance frequency. Conclusion: The reference values in this study can serve as guidelines for further experimental trials.

DACS A new implantable Hearing system for Moderate to Severe Mixed Hearing Loss

The adequate treatment of the patients with moderate to severe mixed hearing loss (MHL) is not sufficiently possible with conventional hearing aids. These patients have enough cochlear reserve, but the additional middle ear disorder limits the usage of conventional hearing aids (gain limitation and distortion). The second possibility for such patients would be the bone conduction hearing aids, which indicate an insufficient gain for moderate to severe MHL. On the other hand because of good cochlear reserve there isn’t an indication for cochlear implantation. Therefore there is no optimal way to give an adequate gain to patients with moderate to severe MHL.