Introduction
Continuing developments in implant electrode design and improved surgical techniques have resulted in an increasing incidence of preservation of residual acoustic hearing following cochlear implantation. In electric acoustic stimulation stimulation (EAS), a cochlear implant electrode array is inserted into the cochlea and electrical stimulation is used to convey high-frequency information to the user. This is coupled to a hearing aid in the implanted ear that is used to convey information to the user by means of acoustic stimulation. So far the concept of combining simultaneous electric-acoustic stimulation to improve hearing was first described in 1999 by C. von Ilberg and J. Kiefer at the Universitätsklinik, Frankfurt, Germany.
In Japan at Shinsu University, Shin-Ichi Usami and collaborators reported earlier that hearing can be preserved even in the presence of a long implant electrode covering the residual hearing region. In the present paper, Professor Usami et al. report the results of 31 consecutive EAS operations in 30 patients. Hearing preservation and clinical outcome were monitored. The subjects were divided into two groups according to the length of the electrode used. Postoperative evaluation after deep insertion of the electrodes showed that residual hearing was preserved satisfactorily in all 32 ears. Regarding speech perception, both groups showed improved speech discrimination and perception. It is concluded that EAS is beneficial for Japanese-speaking patients, including even those with less residual hearing at lower frequencies.
