75-year-old patient with good hearing in the range of frequencies 125–1500 Hz and deafness at other. The result of pure tone audiometry presented a good hearing in the range of frequencies 125–1500 Hz and deafness at other (Fig. 13.13). The cochlear implantation was used to restore hearing at high frequencies, while preserving low and mid frequency acoustic hearing in the implanted ear. This is described as ENS of the inner ear.