No abstract

Binaural hearing helps normal-hearing listeners localize sound sources and understand speech in noise. However, it is not fully understood how far this is the case for bilateral cochlear implant (CI) users. To determine the potential benefits of bilateral over unilateral CIs, speech comprehension thresholds (SCTs) were measured in seven Japanese bilateral CI recipients using Helen test sentences (translated into Japanese) in a two-talker speech interferer presented from the front (co-located with the target speech), ipsilateral to the first-implanted ear (at +90° or −90°), and spatially symmetric at ±90°. Spatial release from masking was calculated as the difference between co-located and spatially separated SCTs. Localization was assessed in the horizontal plane by presenting either male or female speech or both simultaneously. All measurements were performed bilaterally and unilaterally (with the first implanted ear) inside a loudspeaker array. Both SCTs and spatial release from masking were improved with bilateral CIs, demonstrating mean bilateral benefits of 7.5 dB in spatially asymmetric and 3 dB in spatially symmetric speech mixture. Localization performance varied strongly between subjects but was clearly improved with bilateral over unilateral CIs with the mean localization error reduced by 27°. Surprisingly, adding a second talker had only a negligible effect on localization.

Future studies are warranted to explore the interaction between cognition and CI NR algorithms during an effortful listening task.

All cases presenting to the author have undergone surgical treatment and patients with middle ear disease and treated surgically within 2 months of presentation all showed some recovery in facial nerve function. In those with apical disease the palsy was often present for many years and facial nerve function did not improve but nor did it deteriorate post-operatively in these more long-standing cases. Facial nerve palsy associated with cholesteatoma should be treated surgically as early as possible but recovery can still be anticipated, even if treatment is delayed for up to 2 months.

Better-ear glimpsing (BEG) is a phenomenon that helps understanding speech in the presence of fluctuating, spatially separated distractors. This phenomenon has been studied in normal-hearing (NH) and hearing-impaired listeners but remains untapped in adults with cochlear implants (CIs). Further, it has not been investigated how far providing CIs in both ears can improve BEG over providing a single CI in one ear. In the current study, seven Japanese adult bilateral CI users with post-lingual deafness were recruited. Male and female speech distractors were presented from + 900 and—900 and target questions taken from the Helen sentence test (translated into Japanese, spoken by a native Japanese female speaker) were presented from the front. Speech comprehension thresholds (SCTs) were measured in both a co-located and spatially separated condition with CIs in both ears and only in one ear. BEG was calculated as the difference in SCTs between the co-located and spatially separated condition. BEG noted with bilateral CIs was about 2 dB and with unilateral CI was about 0.3 dB, which is significantly smaller than found in NH listeners. The bilateral benefit noted was about 3 dB indicating the advantage of having CIs in both the ears.