[Clarion 16 cochlear implant (System introduction and use experience in Japan].

The Clarion cochlear implant was developed in the USA and received FDA approval in August 1996. It consists of an implantable cochlear stimulator (ICS), speech processor with headpiece, and in addition, a clinician's programming system and portable cochlear implant tester. One of the features of the device is its stimulation-coding process for which two methods of continuous interleaved sampling (CIS) and compressed analogue (CA) are applicable. Regardless of which is used, stimulation can be provided over 8 channels. The device was used in 2 cases. Both patients were operated on in October 1996, and 16 electrodes in 8 pairs were mounted in the cochlea. Mapping, performed 3 weeks after the operation, showed good speech perception in both patients with only a cochlear implant in the "open-set" status. CIS was used as the stimulation-coding method. CA has yet to be applied.

[Effects of chronic electrical stimulation on cochlear nuclear neuron size in deaf kittens].

It is now well recognized that normal afferent innervation is necessary for development of the auditory pathway. This study investigated the effect of chronic electrical stimulation of the auditory nerve on the size of cochlear nucleus somata of neonatally deafened kittens. Four kittens were deafened by using kanamycin and ethacrynic acid at 10 days of age and implanted at various ages with an active intracochlear implant in the left side and a dummy implant in the right side, and chronically electrically stimulated from ages 98-142 days for approximately 1000 hours at twice the EABR threshold. After chronic stimulation or after an equivalent period in the controls, the animals were injected with 2-deoxyglucose (2DG) and stimulated electrically for 45 minutes, then processed for autoradiography. Then the sections were stained for Nissle substance, and the cross-sectional areas (CSSA) of approximately 33,000 neuron somata in the cochlear nuclei were measured with an image-analysis system. Soma sizes in regions with 2DG uptake were compared with those without the uptake. The CSSA of 2DG-labeled regions was usually significantly larger than that of the unlabeled regions, but there were no significant right-left differences. Thus, chronic electrical stimulation of a restricted sector of the cochlea is correlated with a larger soma size in the corresponding region of the cochlear nucleus.

[Testing of synthetic vowels in patients with 22 channel cochlear implant].

In the 22 multi-channel cochlear implant system, F0 information determines the frequency of electrical stimulation, and F1 and F2 information determine the number of stimulating electrodes. We performed tests using synthetic vowels on 16 patients who had undergone 22 channel cochlear implant surgery and 6 months' speech rehabilitation. Information transmission rates were calculated to analyze the response pattern. As a result, 1) the vowel recognition ability of patients with cochlear implant surgery correlated with the number of electrodes being used. 2) The value of vowel confusion decreased so as to be separated by a pair of stimulating electrodes, and the confusion in F1 information was regarded to be less than that for F2 information.