- Published on 16 January 2015
Later, an interesting study was presented by Bruce Gantz from the USA on the future of cochlear implants. It examined the area of acoustic and electric signal processing and trying to understand how much has been learned in the last 15 years about the auditory system. More than 1500 adults with postlingual deafness have been studied at the University of Iowa, USA, since the 1980s in the area of speech recognition. Results showed a constant increase in performance over time thanks to hybrid electric acoustic stimulation. According to Gantz, the benefits of cochlear implants are found in restoration of significant hearing in quiet environments, while in noise there are the same problems as with hearing aids. In addition, they do not provide good quality of sound or music, and the implant may entail the loss of residual hearing. It is also important to remember that low frequency residual hearing maintains better spectral resolution of vocal processing by the cochlear implant. So, what is the future of cochlear implants? How can we guarantee better performance? The answer Bruce Gantz gave was the hypothesis of speech processing to provide temporal fine structure, regeneration of the auditory neural environment and/or hair cells, and other novel electrodes and strategies. He considered that the next change will consist in extending the indications of for electric acoustic stimulation processing with electrodes that better preserve hearing.
In this area, Gantz was referring to functional hearing, i.e. above 85-90 dB in low frequencies that can be amplified with hearing aids, otherwise this would not be useful. Moreover, a number of cited studies have demonstrated that preservation of minimal acoustic hearing does not enhance electric-only speech processing. Gantz presented the results of clinical trials conducted in the United States pointing to the benefits of preserving residual hearing. In conclusion, in his opinion, the future of cochlear implants will require a few adjustments. First, the need for a more robust internal part than what has been used previously, improved preservation of residual hearing in order to improve speech recognition in noise, recognition of music and melody, sound quality, and the ability to locate sound. Second, there is also a need to remember that the central auditory system can reorganize peripheral place pitch if sufficient residual neural environment present to accommodate to shorter electrodes. Third, the need to understand hearing loss following activation of the device (excitotoxicity, trauma, fibrosis) and long-term stability of residual acoustic hearing with a hybrid device. Fourth, selection of electrode lengths; in the future, they may depend on the duration of deafness, patient age, level of preoperation hearing with sufficient neural substrate, and benefit/risk evaluation. Lastly, in the future, selection criteria will include subjects with substantial hearing, and the length of the device will depend on residual hearing, possibly 1.500 Hz and the duration of deafness.