Cochlear prostheses in use: recent speech comprehension results.

Speech-comprehension tests were performed with several deaf volunteers who were equipped with different cochlear prostheses. These prostheses work with inductive transcutaneous signal transmission and contain a multi-channel scala tympani electrode or, in two cases, a disc electrode situated external to the cochlea in the round window niche. The external portable single-channel speech-processor/transmitter used is the same in all cases. The comprehension (stimulation only, no lip reading) of numbers between 1 and 99 on first contact with the stimulator and therefore without any training was around 38% showing that through well designed single-channel stimulation of the auditory nerve it is possible to generate hearing sensations sounding very much like nature hearing impressions. Some open speech comprehension was reached: Through the help of the stimulator, without lip reading, between 60 and 100% of sentences unknown to the completely deaf volunteer, spoken only a little more slowly than normal, are correctly understood. The percentage for isolated unknown words is 60%. Also an important improvement of word comprehension can be achieved through additional stimulation as compared to unaided lip reading. It appears that the most recent design of our cochlear prosthesis can already be regarded as a useful aid for the deaf.