Cochlear implantation in adults

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Arvo building, Jarmo Visakorpi auditorium, address: Arvo Ylpön katu 34.

Kati Härkönen
Photo: Jonne Renvall / Tampereen yliopisto

Doctoral defence of Lic.Med. Kati Härkönen

Cochlear implantation in adults : Extended indications and quality of life

The field of science of the dissertation is Otorhinolaryngology.

The opponent is docent Timo Hirvonen (University of Helsinki). Professor Markus Rautiainen acts as the custos.

The language of the dissertation defence is Finnish.

Extended indications of cochlear implantation in Adults : Hearing, quality of life and working performance

In real-life, conversation often occurs in the presence of background noise. If there is more than one speaker, following and comprehending specific speech requires the ability to locate each sound source. Many people with hearing loss in one ear or both have difficulties to hear in noise. This may lead to problems managing at work and in everyday life. The most common device used to rehabilitate hearing is a hearing aid (HA). In severe hearing loss, a cochlear implantation is used. Cochlear implant (CI) is an electronic medical device that replaces the function of the damaged inner ear. The HA amplifies the sound, but the CI do the work of damaged parts of the inner ear to provide sound signal to the brain. Nowadays, children with profound bilateral hearing loss get CIs to both ears, but adults usually only get one CI. Increasing health care costs exclude the possibility for a second CI in many countries.

In the first study, we evaluated the benefits of bilateral cochlear implantation in 15 adult patients, who had bilateral progressive hearing loss. Results indicated that bilateral CIs provided better opportunities to manage at work and in everyday life than unilateral CI. In addition, sound localization performance and hearing in noise improved. Furthermore, bilaterally implanted patients had less depression and distress after the second cochlear implant.

In the second study, we explored the advantages of CI in seven single-sided deafness (SSD) adult patients. Study showed that working performance, QoL, QoH, sound localization performance and hearing in noise improved. Tinnitus perception in the implanted ear decreased after the cochlear implantation.

In the third study, we explored long-term hearing results, QoL, QoH, work- related stress, tinnitus, and balance problems in 172 adult patients after unilateral idiopathic sudden sensorineural hearing loss (ISSNHL). Poor hearing outcome correlated with severity of initial hearing loss and vertigo and age together with ISSNHL. Patients with recovered hearing had statistically significantly better QoL and QoH, and they had less tinnitus and fewer balance problems. Hearing deteriorated as a function of age similarly in both the affected and healthy ear and ISSNHL did not appear to accelerate the hearing loss.

 In the fourth study, we evaluated the long-term effects of hybrid cochlear implant (HCI) on QoL, QoH, and working performance in eight adult patients, and compared these results to patients with study 1 and 2. HCI combines the electrical stimulation of high-frequency hearing and the acoustic stimulation of low-frequency hearing. Hybrid cochlear implantation improved QoL, QoH, and working performance and the results were comparable with SSD patients with CI and patients with bilateral CIs.

Our studies showed that binaural hearing clearly improved QoL and QoH in all study groups. Working performance, sound localization and hearing in noise were also better after cochlear implantation.


The dissertation is published in the publication series of Acta Universitatis Tamperensis; 2344, Tampere University Press, Tampere 2018. The dissertation is also published in the e-series Acta Electronica Universitatis Tamperensis; 1849, Tampere University Press 2018.

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