gms | German Medical Science

Introduction: In pre- and postoperative cochlear implant (CI) evaluation, speech recognition (SR) is typically measured using monosyllabic words in quiet, which is applicable to prove general ability for SR. However, many aspects that patients are exposed to in everyday life are not taken into account, like diffuse background noises, turn-taking talkers, different voices or divided attention. The group of CI patients includes patients with normal hearing on the contralateral side (Single-Sided Deafness, SSD) as well as patients wearing a hearing aid on the contralateral side (Bimodal, BiM). This study investigated the differences between SSD and BiM patients for a complex multi-talker SR test paradigm, that has never been measured with CI patients before.

Methods: Eighteen adult cochlear implant users participated (8 SSD, 10 BiM). Monosyllabic word recognition in quiet was measured using the Freiburg Monosyllabic Test in free field conditions at 65 dB SPL with CI only. The adaptive CCOLSA [1] was used to measure the speech rate at which a subject reaches 50 percent correct responses for the CCOLSA dual task [2] presented 5 dB above the individual speech reception threshold (SRT) measured in diffuse noise. Furthermore, individual selective attention benefits were assessed using CCOLSA with fixed speech rates comparing Single- and DualTask conditions. CCOLSA was measured best aided.

Results: The monosyllabic word recognition of the two groups did not differ significantly. In contrast, SSD showed significantly lower SRT scores than BiM in diffuse noise (+0.2 dB compared to +3.6 dB median SRT) and reached significantly higher speech rates than BiM performing the adaptive CCOLSA. Furthermore, the SSD group showed a significant improvement of 30 percent points correct responses (median) in the single task (selective attention condition) compared to the dual task (divided attention condition), whereas BiM did not show a significant difference.

Conclusions: Performing the CCOLSA is feasible for both SSD and BiM patients. The results suggest that the hearing loss on the acoustically hearing ear of BiM patients leads to a retardation in cognitive processing of speech and a limitation of selective attention abilities.