Preservation of residual hearing after cochlear implant surgery with slim modiolar electrode

Matti Iso-Mustajärvi,Heikki Löppönen,Sini Sipari,Aarno Dietz

doi:10.1007/s00405-019-05708-x

Abstract

PurposeTo evaluate the insertion results and hearing preservation of a novel slim modiolar electrode (SME) in patients with residual hearing.MethodsWe retrospectively collected the data from the medical files of 17 patients (18 ears) implanted with a SME. All patients had functional low frequency hearing (PTA (0.125–0.5 kHz) ≤ 80 dB HL). The insertion results were re-examined from the postoperative cone-beam computed tomography scans. Postoperative thresholds were obtained at the time of switch-on of the sound processors (mean 43 days) and at latest follow-up (mean 582 days). The speech recognition in noise was measured with the Finnish matrix sentence test preoperatively and at follow-up.ResultsThe mean insertion depth angle (IDA) was 395°. Neither scala dislocations nor tip fold over were detected. There were no total hearing losses. Functional low-frequency hearing was preserved in 15/18 (83%) ears at switch-on and in 14/17 (82%) ears at follow-up. According to HEARRING classification, 55% (10/18) had complete HP at switch-on and 41% (7/17) still at follow-up. Thirteen patients (14 ears) were initially fitted with electric–acoustic stimulation and seven patients (8 ears) continued to use it after follow-up.ConclusionsThe preliminary hearing preservation results with the SME were more favorable than reported for other perimodiolar electrodes. The results show that the array may also be feasible for electro-acoustic stimulation; it is beneficial in that it provides adequate cochlear coverage for pure electrical stimulation in the event of postoperative or progressive hearing loss.

Highlights

The preservation of the delicate inner ear structures has become a major consideration in cochlear implant surgery as intracochlear trauma has been shown to negatively affect the post-implant hearing results [1,2,3,4,5]
First described by von Ilberg et al [6], the physiological acoustic stimulation in the low frequencies combined with the electric stimulation by the cochlear implant has been shown to enhance the postoperative hearing results in terms of better sound quality, improved music listening abilities and better speech recognition against background noise [7,8,9,10,11] residual hearing can be preserved with longer lateral wall electrodes (LWE), much more favorable results have been reported for shorter LWE
Speech recognition was measured with the novel Finnish Matrix Sentence Test (FMST), the standard speech-in-noise test was used in adult CI recipients to measure hearing performance [28, 29]

Summary

Introduction

The preservation of the delicate inner ear structures has become a major consideration in cochlear implant surgery as intracochlear trauma has been shown to negatively affect the post-implant hearing results [1,2,3,4,5]. Due to the more advanced surgical techniques and more delicate electrode arrays, post-operative results have improved during recent years. This has led to an expansion of the use of these devices, including patients with functional residual hearing. First described by von Ilberg et al [6], the physiological acoustic stimulation in the low frequencies combined with the electric stimulation by the cochlear implant has been shown to enhance the postoperative hearing results in terms of better sound quality, improved music listening abilities and better speech recognition against background noise [7,8,9,10,11] residual hearing can be preserved with longer lateral wall electrodes (LWE), much more favorable results have been reported for shorter LWE.

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