[Signal processing and clinical results with the French cochlear implant Digisonic]

The Digisonic is a totally digitised multichannel cochlear implant remarkable for the versatility of its sound signal processing. Owing to its flexible and articulated array, its 15 electrodes are usually introduced in the scala tympani. A special version of this device has been designed to be used in case of total obstructed cochlea. It consists of separated electrodes which may be inserted one by one in the inner ear in different holes gently drilled in the bony cochlea. The possibilities of the microprocessor allow the speech therapist to carefully select the best width and mean value of each frequency band respectively devoted to each functional electrode. These parameters may be adapted to progressively improve the patient's hearing performances as a function of his phonemic discrimination and or the number and the tonotopy of his functional electrodes. Moreover, owing to the versatility of this digitised emitter a lot of speech coding strategies may be easily programmed as a function of eventual desiderata. Its high miniaturisation leads this implant to be particularly useful for young children. Results of our 38 first implanted patients (age 2-74; mean 42) including 7 cases of totally obstructed cochlea are reported.