Hearing with combined electric acoustic stimulation

Abstract

After cochlear implantation, individuals with sufficient residual hearing in the lower frequency region are able to successfully combine acoustic and electrical stimulation patterns to improve speech perception, especially in noise, and to improve music appraisal as well. These improvements occur through enhanced transmission of fine structure information by more accurate mapping of the fundamental frequency contour through acoustic hearing. In current cochlear implant systems, the transfer of frequency and melodic contour is very coarse, and the correct detection of pitch contour requires large frequency differences. It is assumed that the acoustically transferred part of the signal enables the cochlear implant recipient to better segregate between speech signals and interfering sounds. The detection and following of a speech signal emitted by a single talker in a multitalker babble situation is improved when fundamental frequencies as grouping cues are present. The preservation of hearing in the implanted ear must be considered a major surgical challenge. The development of very flexible and soft electrode carriers in combination with surgical approaches that minimally traumatize the inner ear enable hearing preservation in nearly all cases.

Sensitivity to interaural time differences and localization accuracy in cochlear implant users with combined electric-acoustic stimulation

“…For patients with substantial residual hearing in the lower frequency range but poor speech perception, implantation of a CI with hearing preservation (soft surgery procedure) enables combined electric-acoustic stimulation (EAS) to provide enhanced hearing and restore speech perception [15]. The first EAS results were described by von Ilberg et al in 1999 [16].…”

Einfluss des Überlappungsbereichs zwischen akustischer und elektrischer Stimulation

“…Diese Systeme bestehen aus zwei verschiedenen Komponenten: ▪ einer Akustik-Einheit zur Versorgung des residualen Tieftongehörs, sowie ▪ einem Cochlea-Implantat (CI) zur direkten elektrischen Stimulation des weiter basal gelegenen Hörnervbereichs [2]. Die Ergebnisse der EAS-Versorgung zeigen ein vorteilhaftes Sprachverstehen im Störgeräusch sowie eine Verbesserung der Abbildung von Musik durch genauere Frequenzdiskrimination [3][4][5][6][7][8].…”

Residual low-frequency hearing after early device activation in cochlear implantation

“…The advantage of using a hearing preservation technique for CI surgery [18][19][20] is that the acoustic low-frequency residual hearing can be used for electric-acoustic stimulation (EAS). It is a combination of acoustic stimulation via hearing aid function in the apical area of the cochlear and electrical stimulation of the basal parts of the cochlear [5,21]. The use of low-frequency residual hearing in EAS patients leads to an improvement in speech recognition [22].…”

“…Since the introduction of the CI, the indication criteria have been expanded. Initially only completely deaf patients were treated with a cochlear implant [ 5 ], later also patients with low-frequency residual hearing [ 6 ]. Also the treatment procedure has changed over time.…”