Improvements were found regarding the hearing and the tinnitus. Not all participants benefit from the CI to the same degree and in the same situations.The results indicate that cochlear implantation in subjects with unilateral severe to profound hearing loss and ipsilateral tinnitus may be beneficial on a case-to-case basis. Further work needs to be performed to define the appropriate indication criteria.

HP is possible in the majority of subjects who are implanted with a TFEA20, 24, or 28. Using shorter arrays led to greater HP and lower median HL.

Today, cochlear implantation is the treatment of choice in the case of severe to profound hearing loss, but the speech perception abilities of many recipients in noisy conditions are still poor and the overall sound quality and ease of listening still require improvement. Residual low-frequency hearing has been associated with improved hearing performance in cochlear implant patients, especially in difficult listening environments (i.e. cocktail party effect). It seems that low-frequency information can enhance the segregation of competing voices, which leads to better speech understanding in noise. We investigated the effect of low-frequency hearing on speech perception performance in a group of subjects being implanted with the Nucleus Hybrid-L device. The Hybrid-L device is a modified Nucleus Freedom implant, which instead of the standard electrode carries a very delicate electrode array that allows preservation of residual hearing to a great extent. Sentence test results from 22 subjects are presented here. Additionally, for 8 subjects, the acoustically presented frequency range was limited to 300, 500 and 700 Hz, and speech perception tests with a single competing talker were conducted. The Hybrid-L study group achieved a speech reception threshold of 15.9 dB in the hearing aid alone condition, 10.8 dB in the cochlear implant alone condition, and 3.9 dB when using the combination of cochlear implant and hearing aid. Differences between the 3 conditions are statistically significant. Results from the additional experiment on the acoustically presented frequency range suggest that very limited residual hearing below 500 Hz is already sufficient to produce a significant improvement in speech perception performance in conjunction with a cochlear implant.

A significant binaural advantage of 37% was observed for speech recognition in noise. Binaural lateralization ability was statistically superior for the first and second implanted ear (p = 0.009, p = 0.001, respectively). Binaural experience was shown to correlate moderately with absolute binaural speech recognition scores, with binaural advantage for speech recognition and with binaural lateralization ability. The time interval between implants correlated in an inverse direction with binaural advantage for speech recognition.