Johannes Schnabl

Sheep as a Large Animal Model for Middle and Inner Ear Implantable Hearing Devices: A Feasibility Study in Cadavers

Objective Currently, no large animal model exists for surgical-experimental exploratory analysis of implantable hearing devices. In a histomorphometric study, we sought to investigate whether sheep or pig cochleae are suitable for this purpose and whether device implantation is feasible. Methods Skulls of pig and sheep cadavers were examined using high-resolution 128-slice computed tomography (CT) to study anatomic relationships. A cochlear implant and an active middle ear implant could be successfully implanted into the sheep’s inner and middle ear, respectively. Correct device placement was verified by CT and histology. The cochlear anatomy of the sheep was further studied by micro-CT and histology. Results Our investigations indicate that the sheep is a suitable animal model for implantation of implantable hearing devices. The implantation of the devices was successfully performed by access through a mastoidectomy. The histologic, morphologic, and micro-CT study of the sheep cochlea showed that it is highly similar to the human cochlea. The temporal bone of the pig was not suitable for these microsurgical procedures because the middle and inner ear were not accessible owing to distinct soft and fatty tissue coverage of the mastoid. Conclusion The sheep is an appropriate large animal model for experimental studies with implantable hearing devices, whereas the pig is not.

Active middle ear implantation in elderly people: a retrospective study.

Objective: To evaluate the outcomes of younger (<60 yr) and older (≥60 yr) patients implanted with the Vibrant Soundbridge (VSB). The aim was to determine if there were differences between groups. Method: A retrospective study was used to evaluate all patients who were implanted and fit with a VSB during 2008 and 2009 at the Department of Otorhinolaryngology-Head and Neck Surgery, Medical University Innsbruck. Differences in audiologic, medical, and surgical outcomes between younger and older patients were evaluated. Results: No patients had major complications during or after the surgical procedure. All patients had a good hearing benefit as supported by improvements in hearing thresholds from the preoperative to the postoperative condition in the sound field. There were differences between groups in speech understanding postoperatively; however, the differences were not statistically significant. Conclusion: All patients had, independent of age, good audiologic benefit from VSB use. Based on the low risk of medical or surgical complications, the easy use of the hearing implant, audiologic improvements, and potential social benefits, we think that the VSB should be regularly offered to adults with hearing loss, whether they are young or old.

Intraoperative measurement for a new transcutaneous bone conduction hearing implant.

Objective To investigate the possibility of using a modified reverse transfer function (RTF) measurement intraoperatively during surgery of a new transcutaneous bone conduction hearing implant to evaluate the status of the device. Methods Tests were performed on a cadaver skull (preclinically) and two conductive hearing loss patients implanted with a new transcutaneous bone conduction implant. During intraoperative activation, the RTF was measured using a microphone attached perpendicularly and directly to the skin in the middle section of the forehead. Results The RTF could be measured for all frequencies from 500 to 6, 000 Hz. Conclusion The usage of an intraoperative RTF measurement may be a good method to verify the mechanical coupling of the bone conduction floating mass transducer and to test the functional integrity of the implant in an objective way.

Magnetic Resonance Imaging Compatibility of a New Generation of Active Middle Ear Implant: A Clinically Relevant Temporal Bone Laboratory Study.

Objective: Magnetic resonance imaging (MRI) has become an essential tool of modern medical imaging and disease diagnosis. In November 2014, a new MRI-conditional (up to 1.5 T) generation of an active middle ear implant (AMEI) was released to the market. The aim of the study was to test the MRI compatibility of the new implant system in a clinical-anatomical study. Design: Experimental cadaver head model. Setting: Temporal bone laboratory. Participants: AMEIs were implanted in 28 fixed temporal bones at three different floating mass transducer (FMT)-coupling positions (N = 8 short process of the incus, N = 16 long process of the incus, N = 4 round window). Main Outcome Measures: The position of the FMT and the integrity of the ossicular chain was monitored through microscopy, microendoscopy, and computed tomography (CT) scans before and after the MRI (1.5 T) was conducted. Proper function of the implant was tested with reverse transfer function (RTF) measurements. Results: Neither positional nor functional changes after MRI were observed. Conclusion: The new generation of the AMEI is a MRI-compatible system, which features an easier and quicker implant fixation method. The option of MRI in patients with AMEI should be taken into consideration during the preoperative discussion with potential candidates.

Postoperative changes in telemetry measurements after cochlear implantation and its impact on early activation.

Cochlear implantation is a clinically routine treatment for patients with severe sensorineural hearing loss for over 20 years. Up to now, the general recommendation for speech processor activation was 4 weeks after cochlear implantation. The aim of this study was to determine whether activation is possible at <4 weeks postop and to show the postoperative change in telemetry over time.

Vibrant Soundbridge in Children

Objective: The VSB is an AMEI which is approved for children. It is also used for patients with aural atresia or chronic otitis media (COM), with limited hearing rehabilitation solutions. The aim for this study is to investigate the hearing rehabilitation in children using VSB suffering from atresia or COM. Method: Standard audiological tests were performed pre- and postoperatively. CT images were acquired to assess feasibility of the FMT placement in the middle ear and to determine the Jahresdorfer score in patients with atresia. Functional gain and speech improvement are analyzed. Results: Thirteen children (median age 9.1) with congenital aural atresia or COM were implanted with the VSB. The average Jahresdorfer scale was 5.9. There were no pre- or postoperative medical complications observed, and hearing levels were preserved. The surgical technique is safe, due to the unchanged pre- versus postsurgery BC levels. CT images provide crucial information about the accessibility for the attachment of the FMT. Patients with atresia showed a functional gain of 40 dB and an improvement of 60% in speech. Patients with COM showed a functional gain of 38 dB and an improvement of 50% in speech. Conclusion: In these cases, the audiological outcome shows an effective gain in hearing and an improvement in speech. The VSB therefore offers an excellent audiological rehabilitation intact skin solution for children suffering with congential aural atresia or COM.