gms | German Medical Science

Introduction: After a fixed patient group that was supplied in a bimodal condition, cochlear implant (CI) and contralateral hearing aid (HA) (n=25) was compared with one simultaneously bilaterally cochlear implant supplied group (n=20). It was proved that the combination supply of deaf-aid and CI can achieve absolutely better results in the background noise than a bilateral CI supply. Thus the question occurs to a clear indication boundary between a contralateral HA and a 2^nd CI (sequentially bilateral CI-supply).

Material and methods: Within the routine tests a bimodal CI-patients group (n=54) was tested with a CI alone and with the bimodal supply. The test battery was carried out as follows: Freiburger monosyllable test in quiet, the speech understanding in noise HSM-sentence test of SNR +10 dB, and Competing-talkers test 10 dB in the free field. The HA was switched off in that case at the CI test alone. The period of time was between September 2009 and May 2010.

Results: It is proved that the patients in bimodal condition had a better speech understanding in noise when the hearing aid was contributed to the CI than using the CI only. Comparing the HSM-test +10 dB and the Competing talker test 10 dB no significant differences were shown. The tonal remaining hearing ability was put in correlation to the speech understanding test in noise. The speech understanding sentences tests in noise were determined in different frequency ranges. It turned out that, when the hearing-loss in the tonal remaining hearing was at 250 Hz and 500 Hz and the hearing loss between 40 dB to 80 dB the benefit of the hearing aid was most significant. A hearing-loss of less than 40 dB was not a decisive factor in speech understanding in noise. In the high-frequency fields the audiogram shows no significant output.

Discussion: The aim of the research was to define an indication boundary between HA and 2^nd CI by means of the threshold of hearing and speech understanding tests in noise with a great number of patients.

The bimodal supply form shows a clearly better speech understanding than the unilateral supply does. It could be proved that the deep frequency range is important for the bimodal benefit. Patients who had a remaining hearing of at least 40 dB showed the greatest benefit whereas those of hearing loss of more than 80 dB did not have a benefit from the HA.