Oliver F. Adunka

Combined Electric and Acoustic Stimulation of the Auditory System: Results of a Clinical Study

Combined electric and acoustic stimulation (EAS) of the auditory system is a new therapy for patients with severe to profound high- and mid-frequency hearing loss but remaining low-frequency hearing. In a prospective study, 13 patients with low-frequency hearing of better than 60 dB below 1 kHz were implanted with a MED-EL COMBI 40+ cochlear implant. Pure tone thresholds as well as monosyllabic word scores and Hochmair-Schulz-Moser sentences in quiet and in noise were measured with hearing aids, cochlear implant alone and in the combined stimulation mode (EAS) in the same ear. Hearing could be partially preserved in 11 out of the 13 patients. All patients scored significantly higher with cochlear implant alone than with hearing aids. Seven patients scored higher in the EAS mode than with cochlear implant alone for sentences in noise, 4 remained unchanged, and 2 could not use EAS. Synergistic effects of EAS were most prominent for hearing in noise with increases of up to 72% as compared to cochlear implant alone.

Ipsilateral Electric Acoustic Stimulation of the Auditory System: Results of Long-Term Hearing Preservation

Objective: To evaluate long-term ipsilateral hearing preservation in patients who underwent cochlear implantation for the combined electric acoustic stimulation of the auditory system. Methods: This was a prospective observational study conducted at a tertiary referral center. Twenty-three subjects were implanted with the MED-EL C40+ standard or C40+ medium electrode using an atraumatic surgical protocol via an anterior-inferior cochleostomy approach. The desired insertion depth was 18–24 mm or 360°. All patients showed significant low-frequency hearing prior to surgery and monosyllabic word scores did not exceed 40% in the best aided condition. Pure-tone audiometry was performed prior to implantation and at distinct intervals after surgery. Results: Nine patients (39.1%) showed complete pure-tone audiometric hearing preservation (0–10 dB) over an average of 29 months. Seven subjects (30.4%) showed partial preservation of residual hearing (hearing loss 15–40 dB) until an average of 25 months. Delayed loss of residual hearing was observed in 5 cases (21.7%) and 2 patients (8.6%) completely lost residual hearing during or immediately after surgery. Freiburger Monosyllabic word understanding scores in a group of patients with complete hearing preservation increased from 13.1% preoperatively to 75% in the electric acoustic stimulation condition. Conclusion: This study documents that complete and partial preservation of ipsilateral hearing after cochlear implantation can be achieved in about 70% of cases over an average period of 27.25 months when using 360° electrode insertions.

Impact of electrode insertion depth on intracochlear trauma

Objective To assess the effect of cochlear implant (CI) insertion depth and surgical technique on intracochlear trauma. Study Design and Setting Twenty one fresh human temporal bones were implanted with CI electrodes and underwent histologie processing and evaluation. Specimens were grouped into 3 categories: 1) soft implantation technique and standard electrode; 2) soft implantation technique and flexible prototype array; 3) forceful implantations and standard electrode. Based on the grading system (1 to 4), 2 numeric values were calculated indicating the overall severity of cochlear damage (trauma indices). Results Mean trauma index values were 13.8, 36.3, and 59.2 for group 1, 2, and 3, respectively. Differences in cochlear trauma (trauma index) were nonsignificant between specimens in groups 1 and 2 but were significant between groups 1 and 3. Conclusion This study gives evidence that intracochlear trauma increases with deep insertions. Thus, in cases where cochlear integrity might be important, limited insertions should be achieved. Conclusion This study gives evidence that intracochlear trauma increases with deep insertions. Thus, in cases where cochlear integrity might be important, limited insertions should be achieved.

Electric acoustic stimulation of the auditory system: results of a multi-centre investigation.

Conclusion. A high rate of hearing preservation during cochlear implantation for electric acoustic stimulation (EAS) is possible, even when surgery is conducted by a number of different surgeons. Objectives. This study aimed to determine the degree of hearing preservation using surgery for EAS in a European multi-centre clinical investigation. It also aimed to demonstrate the effect of EAS in individuals with residual low frequency hearing, both on speech perception and on subjective quality of life measures. Patients and methods. Eighteen patients with profound high frequency hearing loss were recruited in five participating European centres. Subjects were assessed based on an audiologic test battery, as well as on a subjective hearing aid benefit questionnaire. Each subject underwent attempted hearing preservation cochlear implantation using the MED-EL C40+ device with a Medium electrode. Residual ipsilateral hearing and speech discrimination abilities were assessed at defined intervals up to 12 months after the combined electric-acoustic mode was introduced. Results. Results showed that some degree of hearing preservation was possible in 15718 patients. All subjects showed statistically significant benefit on all three speech perception tests over time. These significant benefits were also reflected in the subjective benefit outcomes.

Electric-Acoustic Stimulation of the Auditory System: A Review of the First Decade

Electric-acoustic stimulation (EAS) was developed for individuals with a profound hearing loss in the high frequencies and a substantial residual low-frequency hearing (LFH). For this group of candidates, conventional hearing aids often neither provided sufficient amplification nor were they considered suitable for cochlear implantation due to the possible destruction of residual hearing capabilities. With EAS, combining electric stimulation with an ipsilateral acoustic stimulation, preservation of residual LFH and the development of a new speech processor uniting both strategies became essential. Over the last years, EAS has developed further and advanced in electrode design and surgery techniques. This paper summarizes the history of EAS and acknowledges the tremendous work of the many research groups who contributed to the success of EAS.

Internal auditory canal morphology in children with cochlear nerve deficiency

Objective: To describe the internal auditory canal (IAC) and inner ear morphologic characteristics of children with cochlear nerve (CN) deficiency. Study Design: Retrospective case series. Setting: Tertiary referral center. Patients: Fourteen children with small or absent (deficient) CNs have been identified by means of high-resolution magnetic resonance imaging (MRI). Interventions: MRI of the brain. Clinical evaluation. Main Outcome Measures: Review of medical records, audiological testing results, and imaging studies. Images were evaluated for the structure of the cochlear, vestibular and facial nerves, IACs and inner ears. Audiometric thresholds were evaluated in all subjects. Methods: Fourteen children with small or absent (deficient) CNs have been identified by means of high-resolution MRI. A review of the medical records, audiologic testing results, and imaging studies was undertaken. The images were evaluated for the structure of the cochlear, vestibular and facial nerves, IACs, and inner ears. The audiometric thresholds were evaluated in all subjects. Results: Among the 14 patients, 5 had known syndromes. MRI allowed an exact specification of the nervous structures within all ears with normal-size IACs. Precise characterization of the nerves in ears with small IACs was more difficult, requiring a consideration of both imaging findings and functional parameters. Five children had bilateral deficient CNs, whereas the remaining 9 subjects were affected unilaterally. Thus, 19 ears had CN deficiency (absent CN, 16; small CN, 3). Eleven ears had normal-size IACs and deficient CNs. Of the 9 ears with small IACs, 8 had deficient CNs (absent, 7; small, 1) on the basis of both MRI and functional assessments. Two ears with small IACs had clear morphologic and/or functional evidence for the presence of a CN: one had a small-size CN on MRI, whereas another had a single nerve in a small IAC with present facial and auditory functions. Conclusion: The findings of this study suggest that CN deficiency is not an uncommon cause of congenital hearing loss. The findings that most ears with CN deficiency had normal IAC morphology and that two ears with small IACs had CNs present indicate that IAC morphology is an unreliable surrogate marker of CN integrity. On the basis of these findings, we think that high-resolution MRI, rather than CT imaging, should be performed in all cases of pediatric hearing loss, especially in those cases where profound hearing loss has been documented. For ears with small IACs, the resolution of MRI currently remains limiting. In these cases, the determination of CN status frequently requires a variety of anatomic (CT and MRI) and functional tests (auditory brainstem response, otoacoustic emissions, behavioral audiometry, and physical examination).

Value of Computed Tomography in the Evaluation of Children With Cochlear Nerve Deficiency

Objective: To assess the predictive value of high-resolution computed tomography (HRCT) in the evaluation of children with cochlear nerve deficiency (CND). Study Design: Retrospective review of medical records. Setting: Tertiary referral center, hospital setting. Patients: Nineteen children (31 ears) with CND. Interventions: Magnetic resonance imaging (MRI), HRCT, and audiologic evaluation. Main Outcome Measures: Comparisons of the morphology of the internal auditory canal (IAC), the bony cochlear nerve canal (BCNC) as seen on HRCT, and audiologic data. Results: Of 12 ears with MRI evidence of an absent cochlear nerve (CN) and a normal-size IAC, all had a patent BCNC as revealed by HRCT. Four of these ears failed auditory stimulation after cochlear implantation, confirming clinically significant CND. Of 15 ears with a narrow IAC and a single nerve visible on MRI, 2 (13.3%) had a normal-size BCNC, 4 (26.7%) were narrow, and 9 (60.0%) were absent. One ear with a narrow IAC, normal BCNC, and a single nerve as revealed by MRI has benefited from cochlear implantation. Conclusion: Using BCNC patency, as revealed by HRCT, as a means of identifying CND would miss all cases of absent CNs in the setting of a normal-size IAC. Thus, MRI should be the primary modality for imaging children with severe to profound sensorineural hearing loss. When MRI demonstrates a single nerve within a narrow IAC, the addition of HRCT can further identify more than half of these cases as involving absent CNs because of an absent BCNC. In a subset of patients, CN status remains indeterminate.

Scala tympani cochleostomy II: topography and histology.

Objective: To assess intracochlear trauma using two different round window‐related cochleostomy techniques in human temporal bones.

Preservation of Basal Inner Ear Structures in Cochlear Implantation

The aim of this report was to examine basal trauma in implanted human temporal bones and discuss modified approaches to the basal cochlear turn to avoid destruction of basal cochlear structures. Thirty-three human temporal bones were implanted with four different cochlear implant electrode arrays manufactured by MED-EL using either a caudal approach cochleostomy or round window membrane insertions. All specimens were processed with a special histological technique that allows sectioning of undecalcified bone with the electrode in situ. All bones were evaluated histologically in terms of basal cochlear trauma. Two pathomechanisms of basal trauma could be distinguished and were evaluated separately, buckling of the basal end of the array and trauma by drilling. Using the caudal approach cochleostomy, the total percentage of destructive basal trauma was 48% compared to less than 15% when performing round window membrane insertions. Although it is still unclear whether basal cochlear trauma influences apical cochlear function or not, adapted surgical procedures and no forceful insertion maneuvers should be used when performing cochlear implantations with hearing preservation.

Cochlear implantation in children with labyrinthine anomalies and cochlear nerve deficiency: implications for auditory brainstem implantation.

Compare outcomes among children with inner ear malformations and/or cochlear nerve deficiency (CND) who have received a cochlear implant (CI).