Bimodal speech perception and prosody recognition in ci recipients with asymmetric hearing loss

A cohort of 12 adults with asymmetric hearing loss (profound in one ear and severe in the other) received an Oticon Neuro ZTI cochlear implant and a Dynamo hearing aid, respectively (bimodal stimulation). Patient age ranged from 16 to 76 years (mean 47.5, SD 24.6). They were tested before implantation (time T0), at month 3, 6 and 12 after CI activation (time 3M, 6M, 12M respectively), by means of: pure-tone audiogram (PTA) in sound booth and in free-field (FF); speech perception (bisillabic words recognition) in free-field (FF) in quiet and with cocktail party; the 48 items SSQ questionnaire (Gatehouse 2004); ASSE test (Govaertz 2006). The performances for all tests were checked in the 3 conditions: bimodal (CI + HA); CI only; HA only. As expected, the speech recognition scores were slightly better in the CI+HA condition than in CI or HA alone, both in quiet and (surprisingly) in noise, although not reaching statistical significance. The SSQ for the bimodal stimulation showed a constant improvement over 12 months, especially for the "quality of sound" sub-scale. The ASSE test returned the most interesting results: the combined (CI+HA) stimulation provided a statistically significant advantage to CI recipients on all the 7 tasks, with a constant improvement over time. The just noticeable difference (JND) was particularly improved in the CI+HA vs the only CI use. This is an evidence of the prosodic enhanchement due to the suprasegmental cues delivered by the HA.