Speech Performance and Sound Localization Abilities in Neurelec Digisonic® SP Binaural Cochlear Implant Users

Abstract

In this prospective study the outcome of the Digisonic® SP Binaural cochlear implant (CI), a device enabling electric stimulation of both cochleae by a single receiver, was evaluated in 14 postlingually deafened adults after 12 months of use. Speech perception was tested using French disyllabic words in quiet and in speech-shaped noise at +10 dB signal-to-noise ratio. Horizontal sound localization in quiet was tested using pink noise coming from 5 loudspeakers, from –90 to +90° along the azimuth. Speech scores in quiet were 76% (±19.5 SD) in the bilateral condition, 62% (±24 SD) for the better ear alone and 43.5% (±27 SD) for the poorer ear alone. Speech scores in noise were 60% (±27.5 SD), 46% (±28 SD) and 28% (±25 SD), respectively, in the same conditions. Statistical analysis showed a significant advantage of the bilateral use in quiet and in noise (p < 0.05 compared to the better ear). Significant spatial perception benefits such as summation effect (p < 0.05), head shadow effect (p < 0.0001) and squelch effect (p < 0.0005) were noted. Sound localization accuracy improved significantly when using the device in the bilateral condition with an average root mean square of 35°. Compared with published outcomes of usual bilateral cochlear implantation, this device could be a valuable alternative to two CIs. Prospective controlled trials, comparing the Digisonic SP Binaural CI with a standard bilateral cochlear implantation are mandatory to evaluate their respective advantages and cost-effectiveness.

Comparison between Bilateral Cochlear Implants and Neurelec Digisonict SP Binaural Cochlear Implant: Speech Perception, Sound Localization and Patient Self-Assessment

“…The presence of the long electrode array under the scalp (in the BINAURAL group) did not result in any specific intra-or postoperative complications, as reported elsewhere [Truy et al, 2002;Verhaert et al, 2012].…”

“…The performances observed in our study were lower, namely 49.9° for the BINAURAL group and 38.2° for the BILATERAL group (in quiet). Verhaert et al [2012] also reported better localization performances in a group of 14 Neurelec Digisonic ® SP Binaural CI users, with an average angular error of 35°. Litovsky et al [2009] noted that stereophonic hearing abilities might emerge in a two-step process beginning with discrimination in noise and converging on more fine-grained localization.…”

“…The performances obtained in the BINAURAL group can be compared with those reported by Verhaert et al [2012] in a multicenter study of 14 subjects implanted with the same Neurelec Digisonic ® SP Binaural CI. The protocol used was similar to ours: speech perception was tested using French disyllabic words presented at 70 dB SPL (10 dB SPL louder than in the present study), in quiet and in noise (steady speech-shaped noise, SNR = +10 dB).…”

“…By virtue of the two signal processing lines, information from the right microphone is sent to the right electrode array, and information from the left microphone is sent to the left electrode array. The stimulation is performed as though the device was made of a single electrode array comprising 24 electrodes; odd electrodes (1, 3, 5, ..., 23) correspond to the 12 electrodes of the ipsilateral electrode array, and even electrodes (2, 4, 6, ..., 24) correspond to the 12 electrodes of the contralateral electrode array [Verhaert et al, 2012]. This technology could be an intermediary solution between unilateral and bilateral implantation, and might provide the benefits of binaural hearing while using a single implant.…”

A Retrospective Multicenter Study Comparing Speech Perception Outcomes for Bilateral Implantation and Bimodal Rehabilitation

“…Consequently, bilateral CI users seem to be favored especially in noise when testing speech intelligibility. When the two CI sound processors become better synchronized, one can hope that the gain will be even greater (Verhaert et al 2012). …”