Magnetic resonance imaging safety of the Combi 40/Combi 40+ cochlear implants.
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Biomedical subjects
Publications and source records attributed to I Hochmair-Desoyer.
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The German HSM Sentence Test, available on compact disc (CD), consists of 30 lists of 20 everyday sentences. It was developed in the desire to have a sufficient number of test sentences for the repeated evaluation of speech understanding of CI users. A noise with speech-shaped spectrum on the CD allows the evaluation of speech understanding in noise. With the HSM Sentence Test we evaluated the speech understanding of participants of the Combi-40 European Multicentric Study. Results are shown for sentences presented without noise and with signal-to-noise ratios of 15, 10, 5 and 0 dB.
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Dimensions of the scala tympani were measured at eight different places of 1 3/4 turns of the cochlea, beginning at the round window. Height and width of the scala tympani do not decrease continuously but show enlargements in some places. The diameter of two types of cochlear implants were compared with the mean heights of the scala tympani. The data provide an anatomical basis for the development of cochlear prosthesis, which could be inserted for a longer distance as accomplished hitherto.
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Design and function of a 6- or 8-channel electrode assembly, which was introduced through the round window into the scala tympani, are described. Two different receiver systems, a more simple one with reed contacts and a more complex one in hybrid technology, are also described. Signal and energy are delivered transcutaneously via inductively coupled coils. The results of the electrical tests are described and discussed.
The present multicentric clinical study involves 19 centres, 16 of them in German-speaking countries, 1 British, 1 Polish and 1 Hungarian. 60 postlingually deafened adults with a mean age of 47.5 years (20-70) and mean duration of deafness of 5.3 years (0.5-20) have been evaluated with the MED-EL COMBI 40 cochlear implant which implements a high-rate continuous-interleaved-sampling strategy with 8 channels. Safety and effectiveness data have been collected. Speech perception tests include a 16-consonant, an 8-vowel, a sentence and a monosyllabic-word test in all languages and a 2-digit figure test in all languages but English. Test intervals are 1, 3, 6 months and 1 year after first fitting. 41 of the 60 postlingually deafened adult study patients have completed their 6-month evaluation. While their pre-operative monosyllabic-word score was 0%, their mean monosyllabic-word score 6 months after first fitting was 48% (8-90) with a median of 50%. The mean sentence understanding was 84% (24-100) with a median of 90%. The respective values for the 1-year evaluations with 25 patients are a mean of 50% (5-85), with a median of 60% for the monosyllables and a mean of 89% (30-100), with a median of 97%, for the sentences.
Revision surgery was successfully performed on two Vienna cochlear implant patients. Twenty months and 40 months, respectively, after initial insertion into the cochleas of two bilaterally deaf patients, electrodes were removed from the scala tympanis and replaced by electrodes of the same design. Psychophysical and speech data gathered before and after the revision surgery were compared. These were thresholds, loudness scalings, amplitude difference limens, pitch scalings, frequency difference limens, and speech tests in the "stimulation only" modality. No negative changes were found. The data available demonstrate a continuous improvement in performance over many months of practice with the sound processor. This development was not impeded by the revision surgery. Thus, it was demonstrated that the removal and replacement of a molded scala tympani electrode is feasible.
The technology of two different multichannel cochlear prosthetic devices is described. The clinical results after electrical stimulation in five implanted patients are discussed.