Residual Hearing Thresholds in Cochlear Implantation and Reimplantation

Abstract

Implant and reimplantation surgery should be carried out with preservation of residual hearing. The aim of this study is to evaluate the effects of such a surgery on hearing threshold. We report the results on 40 patients, 20 males and 20 females, aged between 5 and 70 (mean 29) years, 16 pre-verbal and 24 post-verbal, with measurable pre-operative auditory thresholds. We used the following implants: Advanced Bionics, Med-El, Cochlear, and MXM Digisonic. Four of the patients underwent cochlear reimplantation owing to device failure. A complete insertion was obtained in all patients. Responses to pure-tone stimuli were evaluated in each ear in pre-implant conditions and 3 months after cochlear implant or reimplantation. The explantation was performed with minimal cochlear trauma and preservation of the explanted electrode integrity. 35% showed no change of the hearing threshold, 45% showed a slight worsening of the hearing threshold level in the implanted ear, and 20% had a total loss of residual hearing. Median increases of threshold levels were 10, 5, 10 and 3 dB HL respectively for 125, 250, 500 and 1 kHz. In the group of 4 patients who underwent cochlear reimplantation, 2 showed no variation of the hearing threshold, 1 preserved an appreciable hearing threshold, and 1 had a total loss of residual hearing. The data seem to suggest that hearing function is rather resistant to mechanical trauma during implant and reimplant surgery; the authors hypothesize a role for direct spiral ganglion activation under intense mechanical stimulation.

Loss of Saccular Function after Cochlear Implantation: The Diagnostic Impact of Intracochlear Electrically Elicited Vestibular Evoked Myogenic Potentials

“…The transmission of acoustic stimuli by bone conduction to elicit VEMPs should also be possible because the saccule is neuroanatomically closer to the oval window than to the round window where the cochlear implant electrode was inserted. This is supported by reports of airand bone-conducted residual hearing after cochlear implantation [Gstoettner et al, 2006;Di Nardo et al, 2007]. Unfortunately, all patients investigated in the present study had no significant residual hearing before surgery so that this aspect could not be further investigated.…”

Analysis of Fifty-Six Cochlear Implant Device Failures

“…In 2001, the same group had reported that in a series of 33 reimplantations over 16 years they had measured postoperative performance at equal or better scores than before failure [2] . In a recent publication by Di Nardo et al [12] , the authors investigated residual hearing thresholds that had been retained after initial implantation. In 3 out of 4 individuals residual hearing was even preserved after the reimplantation procedure.…”

Automated insertion of preformed cochlear implant electrodes: evaluation of curling behaviour and insertion forces on an artificial cochlear model

“…These surgical challenges were investigated in numerous studies [34,[36][37][38] showing a strong fluctuation in the success rate. The range of reported complete preservation of residual hearing varies from 26% [34] to 39% [38].…”