Wolf Dieter Baumgartner

Hearing preservation in cochlear implantation for electric acoustic stimulation

Objective To evaluate the possibility of preservation of low-frequency hearing in atraumatic cochlear implant electrode insertion procedures for combined, ipsilateral electric and acoustic stimulation. Material and Methods A total of 21 patients were implanted with a MED EL C40+ cochlear implant using an atraumatic electrode insertion technique to preserve residual low-frequency hearing. Pure-tone audiometric thresholds were measured pre- and postoperatively to evaluate the degree of preserved hearing. Speech discrimination tests in quiet and with background noise were performed in a patient with successful hearing preservation. Results Using the atraumatic electrode insertion procedure with an insertion depth of 360° (18–24 mm), hearing preservation could be achieved in 18/21 patients (85.7%). Three patients (14.3%) lost their residual low-frequency hearing after the implantation. Residual hearing was preserved completely in 13 patients (61.9%) and partial hearing preservation was possible in 5 (23.8%). Preliminary speech discrimination tests showed a dramatic benefit for the combined electric and acoustic stimulation mode compared to cochlear implantation alone. Conclusion Preservation of low-frequency hearing in cochlear implantation is possible in patients implanted because of profound high-frequency deafness. With the development of new, more atraumatic electrode designs, preservation of residual hearing should be further improved.

Follow up of cochlear implanted handicapped children

OBJECTIVE To document progress and benefit of multi-handicapped children using cochlear implants. DESIGN The evaluation of auditory responses to speech (EARS) test battery was performed on the children in this study at regular intervals following implantation. All children went through individually tailored intensive audiological rehabilitation programs following cochlear implantation. RESULTS Individual results from ten multi-handicapped children receiving cochlear implants are presented in this paper. The majority of children in this study are successful implant users. Whenever possible, test scores are included as well as subjective case reports. CONCLUSION Providing multi-handicapped children with cochlear implants can result in substantial benefit for both the child and parents. Multi-handicapped children are not contraindicated for cochlear implantation, although not all are considered to be good candidates.

Cochlear Implant Deep Electrode Insertion: Extent of Insertional Trauma

We have recently undertaken deep insertions of the Combi-40 cochlear implant electrode (Med-E1 Corp., Innsbruck, Austria) into apical regions of the scala tympani using a cochleostomy approach. In order to examine the extent of the insertional trauma, 12 fresh human temporal bones were implanted with original Combi-40 electrodes. The specimens were histologically processed with the implants in place by employing a sawing and grinding technique. In most cases, only very discrete distortions of the epithelium of the spiral ligament occurred within the middle cochlear turns. Furthermore, a slight displacement of the basilar membrane caused by the electrode was occasionally seen. However, in 2 cases more severe damage such as basilar membrane rupture and electrode displacement was found. Attempts to insert the electrode beyond the point of first resistance resulted in electrode kinking within the basal cochlear turn with subsequent fracture of the osseous spiral lamina. According to our results, deep electrode insertions do not aggravate the insertional trauma provided no force is applied when resistance is felt.

Localization of Nitric Oxide Synthase I and III in the Cochlea

Nitric oxide synthase (NOS) isoforms I and III were localized in the guinea pig cochlea by indirect immunohistochemistry using frozen sections and paraffin sections. NOS I staining was observed in the cytoplasm of outer hair cells, in nerve cell somata and fibers of the spiral ganglion, and in axonal profiles of the spiral lamina next to the base of inner hair cells. In addition, lining cells of the inner sulcus and limbus, and cells of the spiral ligament stained for NOS I but vascular walls remained unstained. NOS III reactivity was seen in the cytoplasm of outer and inner hair cell, in lining cells of the limbus, and on the endolymphatic surface of marginal cells. Staining for NOS III of spiral ganglion perikarya showed varying intensity. Endothelial cells of cochlear glomeruli reacted for NOS III. NOS III in vascular endothelial cells implies regulatory effects of nitric oxide (NO) on vascular wall tonus and cochlear blood supply. NOS I in cochlear neurons indicates these cells as possible sources for NO during neuronal activity. Activated neurons may provide NO that adjusts cochlear perfusion to neuronal activity. Finally, NO that is liberated from hair cells or afferent synaptic terminals may act as an inhibitor on N-methyl-D-aspartate (NMDA) receptors (negative feed-back inhibition).

Perimodiolar Electrodes in Cochlear Implant Surgery

Perimodiolar-positioned cochlear implant electrodes have been developed in order to bring the electrode contacts as close as possible to the spiral ganglion cells, which are the target of electrostimulation. This results in lower electrical thresholds, higher dynamic ranges and less channel interaction when compared with normal implant electrodes which are usually located peripherally within the scala tympani. In this study we evaluated 4 different types of perimodiolar electrode: the Clarion Preformed electrode, the Clarion Preformed electrode with positioner, the Nucleus Contour electrode and the Med-El Perimodiolar Combi 40 electrode. These devices require different approaches to achieve a perimodiolar electrode position. The electrodes were inserted in fresh human temporal bones. After processing these bones with the electrodes in situ by employing a sawing, grinding and polishing technique, the inner ear structures as well as the electrode positions could be evaluated in detail. All electrode types studied had a more or less perimodiolar position; however, each type produced a certain amount of trauma to cochlear structures which is discussed in relation to mechanical properties. Further human temporal bone studies with improved perimodiolar cochlear implant electrodes are necessary in order to find an optimized type of electrode.Perimodiolar-positioned cochlear implant electrodes have been developed in order to bring the electrode contacts as close as possible to the spiral ganglion cells, which are the target of electrostimulation. This results in lower electrical thresholds, higher dynamic ranges and less channel interaction when compared with normal implant electrodes which are usually located peripherally within the scala tympani. In this study we evaluated 4 different types of perimodiolar electrode: the Clarion Preformed electrode, the Clarion Preformed electrode with positioner, the Nucleus Contour electrode and the Med-El Perimodiolar Combi 40 electrode. These devices require different approaches to achieve a perimodiolar electrode position. The electrodes were inserted in fresh human temporal bones. After processing these bones with the electrodes in situ by employing a sawing, grinding and polishing technique, the inner ear structures as well as the electrode positions could be evaluated in detail. All electrode types studied had a more or less perimodiolar position; however, each type produced a certain amount of trauma to cochlear structures which is discussed in relation to mechanical properties. Further human temporal bone studies with improved perimodiolar cochlear implant electrodes are necessary in order to find an optimized type of electrode.

The role of age in pediatric cochlear implantation

OBJECTIVE To document progress, benefit and importance of age in paediatric cochlear implantation. DESIGN The EARS (Evaluation of Auditory Responses to Speech) test battery was performed on 33 prelingually deaf children at regular intervals up to 36 months following implantation. All children participated in individually tailored intensive audiological rehabilitation programs after receiving their implants. In this respect, it was attempted to evaluate speech perception scores in children implanted before and after the age of 3 in a homogenous group. RESULTS All children demonstrated encouraging improvements over time in their speech recognition abilities. Furthermore, it was observed that the children who were implanted under the age of 3 achieved higher levels of speech perception performance. CONCLUSION In order to shorten the process of central maturation of the auditory system, it is desirable to implant the children as young as possible. Early intervention seems to be the ideal strategy in enabling prelingually deaf children to derive maximum benefit from cochlear implantation.

Cochlear Implant Deep‐Insertion Surgery

Intracochlear electrode placement in cochlear implant surgery is performed to maximize the chance of stimulating auditory nerve fibers as well as spiral ganglion cells. Using a round window or cochleostomy approach, insertion lengths of the nucleus electrode were found to be 17 to 19 mm.13 A total electrode insertion length of 18 to 21 mm has been described a h r performing a mastoidotomy-tympanotomy approach.4 However, insertion depths of approximately 30 mm are necessary to insert electrodes not only into basal but also into middle and apical cochlear turns. Electrode placement in these cochlear regions would improve the probability of stimulating surviving nerve fibers and provide a better correlation to cochlear tonotopy.5 For this reason, some authors recommend multiple-electrode implantations by drilling additional openings into the second turn of the cochlea.4.6

The Suprameatal Approach in Cochlear Implant Surgery: Our Experience with 80 Patients

The suprameatal approach (SMA) was first performed in 1999. It was developed for cochlear implantation as an alternative to the classic technique of transmastoid posterior tympanotomy approach. In the course of SMA the middle ear is exposed from the external auditory canal and the electrodes are inserted into the cochlea through a suprameatal tunnel bypassing the mastoid cavity. The goal of developing the SMA was to simplify the surgical technique, shorten the duration of surgery, enable wide exposure of the middle ear during the procedure, and avoid possible damage to the facial nerve and chorda tympani. We report here the results of 80 patients who were operated on using the SMA technique.

Short-Term Effect of Auditory Feedback on Fundamental Frequency after Cochlear Implantation

The present study evaluates the short-term effect of cochlear implantation on the fundamental frequency (F0) of 13 deaf patients. All patients were provided with the Combi 40+ cochlear implant. Voice recording was made pre- and 3 months post-implantation. The F0 was analysed using X-Tools software. The results showed that 38 per cent of our subjects had a statistically significant decrease of their mean F0 (p=0.001) at 3 months following implantation. It was also observed that the patients tended to have a lower F0 postoperatively approaching the normal range of F0. A large variability in F0 was noticed among the deaf subjects but no correlation with the duration of deafness was seen. There was also no correlation between speech recognition and speech production.

Hearing Performance in Noise of Cochlear Implant Patients versus Severely-Profoundly Hearing-Impaired Patients with Hearing Aids:Rendimiento auditivo en ambiente ruidoso en pacientes con implante coclear versus hipoacúsicos profundos con auxiliar auditivo

It is possible for most post-lingually deaf patients to attain significant open speech recognition following cochlear implantation. In contrast, many severely-profoundly sensorineural hearing-impaired patients receive no benefit from their hearing aids, especially in situations with background noise. The aim of the study was to evaluate the speech recognition ability in quiet and in noise of post-lingually deaf adults implanted with Combi 40/40+ cochlear implants versus severely-profoundly sensorineural hearing-impaired patients fitted with hearing aids. For this purpose, we tested two groups of patients: one that had received cochlear implants (n=22) and a group of subjects with severe-profound sensorineural hearing impairment, fitted with hearing aids (n= 15). All of the patients were tested using the Hochmaier, Schultz, and Moser Discrimination Test in quiet and noise. The results of the study demonstrate that most of our cochlear implant patients received a substantial benefit from their implant, achieving scores of 70 to 100 per cent (mean, 90 per cent) for the numbers test and 10 to 72 per cent (mean, 43 per cent) for the monosyllable test 1 year after implantation. Even in situations with background noise, scores of 1 to 99 per cent (mean, 45.65 per cent) for a signal to noise ratio (SNR) of + 15 dB 1 year following the implantation improved to 7 to 95 per cent (mean, 50.7 per cent) at 2 years and 8 to 99 per cent (mean, 60 per cent) at 3 years after implantation. These results are significantly (p<0.04) superior to the hearing aid patients’ scores of 1 to 64.2 per cent (mean, 26.7 per cent) for a SNR of 15 dB. The results of the present study may have clinical implications in regard to selection of candidates for cochlear implantation.