A Miniature, Fiber-Optic Vibrometer for Measuring Unintended Acoustic Output of Active Hearing Implants during Magnetic Resonance Imaging.

Making use of magnetic resonance imaging (MRI) for diagnostics on patients with implanted medical devices requires caution due to mutual interactions between the device and the electromagnetic fields used by the scanner that can cause a number of adverse events. The presented study offers a novel test method to quantify the risk of unintended output of acoustically stimulating hearing implants. The design and operating principle of an all-optical, MRI safe vibrometer is outlined, followed by an experimental verification of a prototype. Results obtained in an MRI environment indicate that the system can detect peak displacements down to 8 pm for audible frequencies. Feasibility testing was performed with an active middle ear implant that was exposed to several pulse sequences in a 1.5 Tesla MRI environment. Magnetic field induced actuator vibrations, measured during scanning, turned out to be equivalent to estimated sound pressure levels between 25 and 85 dB SPL, depending on the signal frequency. These sound pressure levels are situated well below ambient sound pressure levels generated by the MRI scanning process. The presented case study therefore indicates a limited risk of audible unintended output for the examined hearing implant during MRI.

Self-assessment of daily hearing function for implant recipients: A comparison of mean total scores for the Speech Spatial Qualities of Hearing Scale (SSQ49) with the SSQ12.

OBJECTIVE: To assess the relationship and agreement between mean total scores for the Speech Spatial Qualities of Hearing Scale (SSQ49) and the shorter SSQ12 to measure daily hearing function for a large group of auditory implant recipients. METHODS: Prospective, longitudinal self-assessment by 1013 implant recipients using the SSQ49 at preimplant and at annual post-implant intervals (one, two and three-years) via an international registry. Mean total scores were calculated for the SSQ49 and the extracted SSQ12 responses. Pearson correlation and Bland-Altman agreement were examined between the SSQ49, SSQ12 and transformed SSQ12 versions. Longitudinal mixed-effects models were used to compare changes over time. RESULTS: Very high correlation was shown between mean total scores for all versions while perfect agreement was not reached. Clinically acceptable agreement (<1.0 unit) between all versions was obtained with the transformed SSQ12 being least biased. All versions showed statistically significant improvement at one-year post-implant (>2.2 units; p < 0.001). CONCLUSIONS: All scale-versions showed comparable sensitivity to changes in self-reported hearing function over time. TheSSQ12 may be considered as a potential time-efficient self-assessment of hearing function for implant recipients in routine practice. Further research may involve independent repeated administration of each scale version.

Medical and Audiological Indications for Implantable Auditory Devices.

Implantable auditory devices (IADs) are a viable hearing restoration option for patients with hearing loss. Conditions such as chronic otitis externa, congenital aural atresia, and chronic otitis media can be treated with a variety of implants. Progressive disease are also amenable to restoration with IADs, providing stabilized hearing. When considering the best rehabilitative options, the patient's preference, ease of surgery, ease of device use, quality of life, and the traditional alternatives (such as ossiculoplasty, hearing aids, and cochlear implants) need to be considered. Patients with conductive, mixed, and sensorineural losses, mild to severe in nature, can be candidates for IADs.