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This article provides an overview of auditory implants. Implanted auditory devices may be classified into bone conduction implants (BCI) and active middle ear implants (AMEI) that stimulate cochlear hair cells, and cochlear implants (CI) that stimulate neural structures. CIs bypass damaged hair cells and directly stimulate the cochlear nerve. They provide better hearing and speech intelligibility than hearing aids (HA) in bilateral severe-to-profound SNHL. They are performed bilaterally to restore directional hearing. CI is also a treatment option for patients with single-sided deafness and intractable tinnitus. CI is poor in music and voice quality appreciation. Improvement of a more non-invasive CI electrode, with a drug delivery system for gene therapy, is being researched. AMEI (Vibrant Soundbridge) is a treatment option for patients with conductive, sensorineural or mixed hearing loss, up to severe thresholds. It functions by coupling a floating mass transducer to the incus or round window. It can be partially or fully implantable. Studies have shown significant improvement in hearing thresholds with AMEI and better speech performance than HA in background noise. Fully implantable AMEI (Carina) is not widely available. Less bulky, fully implantable AMEI will be more attractive treatment options. BCI are a valuable solution for patients with conductive, mixed hearing loss and unilateral SNHL providing maximum amplification of about 45-55dB. They are useful in patients with chronic otitis externa, ear canal atresia, microtia or previous middle ear surgeries. Patients get stable hearing benefit from BCI. The transcutaneous technology of BCI devices (Bonebridge) avoids complications of percutaneous BCI (BAHA) such as skin problems, but maximum amplification may be lower. Candidacy is based on audiological, radiological and psychological workups. Most are currently partially implantable devices. Hopefully, with future technology, there will be more fully implantable auditory devices which will be beneficial to patients with hearing loss.

Advances in auditory implants.
Iwasaki S.
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Praneta Kulloo

Lewisham and Greenwich NHS Trust, UK.

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