The cochlear implant represents one of the medical devices with the greatest impact on people’s quality of life. It was created to artificially restore hearing to people suffering from severe to profound hearing loss. The WHO reports that around 5% of the world’s population (466 million people) experience severe hearing problems, implying that many people may benefit from this technology [1].

Its structure is made up of external and internal units working as a whole, capable of capturing, processing, and transmitting sound from outside to the brain through electrical stimulation applied to the neurons. In detail, its external unit contains microphones, battery, and a processor integrated into a single visible case, worn behind the auricle; and the internal unit contains a mini-processor connected to an array of current-conducting electrodes having the shape of a small tube, which is surgically implanted into the interior of the cochlea organ. Today, this device offers speech perception from the level of silence to a normal magnitude. However, there are limitations on music appreciation, not clearly perceiving speech in noisy environments and poor spatial localization of sound. Additionally, users prefer a smaller and more discreet device, that is, without wearable and visible elements.

The future of the cochlear implant aims to overcome these limitations, providing speech-hearing comparable to normal hearing. In addition, there is an urgency to offer a low-cost and high-quality device as its elevated price limits the massive access in low-income populations. In response, science is exploring solutions whose feasibility is being progressively evaluated. In terms of audio signal processing, the tendency is to apply techniques that avoid firing adjacent electrodes synchronously, minimizing the current overlap that causes poor speech discrimination.

To improve music perception and sound localization, some researchers consider maximizing the fine structures of information and mimicking the natural cochlea function. To save battery power and protect the cochlea structures, it is proposed a pre-curved small tube (array) to place the electrodes close to the auditory neurons. As an alternative, the stimulation by optics has been proposed, that is, nerve cells fire by light instead of electrical current. Another aspect is to avoid damaging structures of the cochlea during surgery. That is, while the doctor inserts the implant, trauma is caused by the strong contact of the electrode array with the walls of the cochlea [2]. To minimize this, science proposes robots that guarantee a smooth insertion. These and more advances are available and in process. Soon, science will offer more powerful cochlear implants, comparable to the functionalities of the human ear.

References:

[1] World Health Organization (WHO). 2019. Fact sheet deafness and hearing loss [Accessed 2020 May 1] Available from: https://www.who.int/en/news-room/fact-sheets/detail/deafness-and-hearing-loss

[2] Mitchell-Innes A, Saeed SR, Irving R. The Future of Cochlear Implant Design. Adv Otorhinolaryngol. 2018;81:105-113. doi: 10.1159/000485540. Epub 2018 Apr 6. PMID: 29794452.