Clinical application of magnetic resonance imaging in 30 cochlear implant patients.

OBJECTIVE: The goal of this investigation was to provide evidence that magnetic resonance imaging (MRI) can be performed safely and effectively on cochlear implant patients who require diagnosis of additional diseases. STUDY DESIGN: A retrospective study was performed over 5 years. In a total of 300 patients with cochlear implants at the authors' center, MRI was performed whenever it was medically indicated. SETTING: All patients underwent scanning in a Philips Gyroscan T10-NT MRI machine, using commercially available Powertrac 3000 software. PATIENTS: All patients with cochlear implants for whom MRI was indicated (n = 30) were included in this study. They had a wide variety of conditions necessitating MRI, including cervical discus prolapse, hypophyseal adenoma, epipharynx carcinoma, knee degeneration, parotid tumor, and preoperative evaluation for reimplantation and bilateral implantation. RESULTS: No adverse effects from the MRI were reported by any of the patients. The cochlear implants all retained their function. All images were of diagnostic value. Because of the MRI, the patients did not need to undergo additional, more invasive and expensive diagnostic procedures. Examples of MRI images from 5 patients are shown. CONCLUSIONS: MRI on cochlear implant patients, using the Med El Combi 40 and Nucleus mini 22 series at 1 Tesla, can be a safe procedure. Removal of any magnet is not necessary.

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.

Speech discrimination scores of postlingually deaf adults implanted with the Combi 40 cochlear implant.

The aim of the study was to assess the speech discrimination ability of postlingually deaf adults implanted with the Combi 40 cochlear implant and to compare the results with the postoperative data published for other devices. The postoperative open and closed set speech perception performance of 21 consecutive patients was tested using a standardized test battery comprising a number, monosyllable, sentence, consonant and vowel discrimination test as well as a rhyme test in the sound only condition. Mean values achieved for each test 1, 6 and 12 months after "switch on" were evaluated. The results demonstrate that all patients have a substantial benefit from their implant and show a continuous improvement in their speech perception abilities with increased device experience. The mean percentages of correct answers after 12 months were 93.4 for numbers, 44.6 for monosyllables, 78.5 for sentences, 67.6 for the rhyme test, 59.8 for vowel, and 67.3 for consonant discrimination. Preoperatively, the mean discrimination score for monosyllables was 0%. The speech discrimination scores of our patients were similar or higher than described for similar patient groups implanted with other devices. The high stimulation rate of the implant system using the continuous interleaved speech processing strategy as well as a deep atraumatic electrode insertion into the apicalmost regions of the scala tympani may be the reason for good performance.

Radical cavities and cochlear implantation.

Profoundly deaf patients with chronic suppurative otitis media have been contraindicated for cochlear implantation in the past. Complications such as infection of the radical cavity, fat necrosis, skin flap problems, change in electrode position and cholesteatoma have occurred in subjects with radical cavities. The aim is to create a dry, self-cleansing, infection-free cavity. This is essential in patients about to receive a cochlear implant, as infection may be introduced into the cochlea at the implantation site and destroy any remaining neural elements. The aim of this paper was to show that it is possible to obliterate the radical cavity and perform cochlear implantation using a one-step surgical technique. Eight patients suffering from long-term bilateral chronic middle ear diseases with chronic sepsis leading to severe hearing impairment underwent cochlear implant surgery. No major complications were observed in these subjects.

Speech perception performance in prelingually deaf children with cochlear implants.

The goals of this study were to report on mean values of speech perception performance in prelingually deaf children implanted with a Combi 40/40 + cochlear implant. A total of 31 patients were included in the study. The time span ranged over 3 years, during which time the Evaluation of Auditory Responses to Speech (EARS) test battery was used with the children. The EARS battery contains four measures of closed-set speech perception and three open-set tests. The mean test results exhibited steady improvement on all parts of the EARS test battery, even up to 3 years post-implantation. The preoperative scores for the Listening Progress Profile (LiP) were 4%, rising to 93% at 36 months post-implantation. Results for the open-set testing measures were most encouraging, with some children reaching fairly high levels of speech perception, receiving scores as high as 100%, by the 36-month evaluation. The congenitally and prelingually deaf children in our study showed continuous improvement in both closed and open set speech perception following cochlear implantation, although variability in individual performance among the children was noted.

Fixation of the electrode array with bone paté in cochlear implant surgery.

The aims of this study are to report on our experiences using a bone paté (a mixture of bone dust and fibrin glue) fixation technique of the Combi 40/Combi 40+ electrode array during cochlear implant surgery. A retrospective study involving 57 patients implanted with Combi 40/Combi 40+ cochlear implants over 31 months fixated with bone paté was performed, utilizing our electrical fitting data as well as re-operation and X-ray findings. We found no signs of electrode retraction in any of the 57 patients. Electrical fitting data showed no reduction in the number of active channels between the first and last times patients were evaluated (a period of 4-31 months). Furthermore, a comparison of X-rays performed within the first week following cochlear implant surgery and again 7-27 months later showed no signs of electrode retraction in 10 patients. Three patients who required re-operations after implantation allowed us the opportunity to examine the effectiveness of the bone paté fixation and revealed new bone growth with the electrode fixed in place. Histological examinations of the newly built bone showed laminar and compact bone structures. The use of bone paté was thus found to be a suitable method of electrode fixation in cochlear implant surgery. Compared with other fixation methods, it is inexpensive and uses no foreign materials.

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.

Intracochlear position of cochlear implant electrodes.

There are many different types of cochlear implants available on the market today and they are constantly being re-evaluated and changed. Knowledge of the exact position of the electrode within the cochlea is important in order to improve the electrical stimulation of the hearing nerve by the implants. The stimulating electrodes are usually located peripherally within the scala tympani, although several attempts have been made to develop peri-modiolar located electrode arrays. In this study, our goal was to evaluate the intracochlear positions of Nucleus, Combi 40/Combi 40 +, and newly developed peri-modiolar positioned electrodes by inserting them into fresh human temporal bones. After insertion, the bones were then histologically processed with the electrodes in situ, following perilymphatic formalin perfusion and methylmethacrylate embedding. Sections of the bones 80-100 microm thick were prepared using a sawing, grinding and polishing technique. This technique resulted in excellent preservation of the inner ear structures and clear identification of each electrode. The different types of electrodes were then evaluated as to their insertion depth, trauma to cochlear structures and location in relation to the scala tympani walls.

Auditory fractal random signals: experimental data and clinical application.

In the mammalian primary cochlear afferents, fractals in the postsynaptic bursting behaviour triggered by a constant perisynaptic release of glutamatergic transmitter agonists have been demonstrated. In order to test the validity of fractally coded auditory signal transmission in man, frequency, intensity and temporal resolution tests were performed in cochlear implanted patients. All patients clearly recognized the fractally coded signals transmitted to the cochlear implants. These first results demonstrate evidence for fractally coded auditory signal transmission in man.

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.

[Rehabilitation of hearing-impaired patients with cochlear implants: a review]. / Rehabilitation Hörgeschädigter mit Cochlear-Implantaten--eine Ubersicht.

The aim of this paper is to provide an overview of the cochlear implant. The history of this entity is traced from the early development of implants, involving the stimulation of the hearing nerve, up to the currently available standard multichannel implants. The physiological background is also elucidated. A cochlear implant consists of an implantable portion which lies within the ear, and of parts that are worn externally on the body. Differences between the first implants and those now in use are as follows: transcutaneous information and energy transmission, the position of the electrode in the ear, and the configuration of the electrode. Differences between the currently available implants mainly concern the number of electrodes, speech coding strategies and the mode of electrode stimulation. Almost all of the most recent implants are equipped with electrodes that are implanted in the tympanic scale of the cochlea.

[Cochlear implantation--the Viennese surgical technique]. / Cochlear-Implantation--die Wiener Operationstechnik.

The aim of the study was to report the current surgical procedure that has been established on the basis of about 200 implantations with the Combi 40/40+ implant system. The outstanding features of this procedure are the skin incision and the fact that the electrode can be inserted up to a depth of 34 mm into the cochlea. In order to provide better magnetic positioning of the external parts, a flap-reducing technique may be required. For insertion we used a soft surgery method to preserve structures within the cochlea. In some cases we were able to inspect the cochlea with microendoscopes, which helped to prevent electrode kinking, since fibrous obliterations were found before the insertion. For electrode fixation in the mastoid cavity we used bone paté.

[Preoperative imaging of the inner ear prior to the implantation of a multichannel cochlear implant using computed and MR technology]. / Präoperative Bildgebung vor dem Einsetzen eines multikanalikulären Cochlear-Implantates mittels Computer- und Magnetresonanztomographie der Innenohrregion.

CT and MRT are now standard examinations prior to insertion of a cochlear implant. Both methods have advantages and disadvantages in terms of discovering potentially pathological structures in the inner ear. The aim of this study was to evaluate the pros and cons of using CT and MRT before cochlear implantation. CT is usually performed using axial planigraphic planes. Like MRT, bone-specific CT is helpful in the diagnosis of congenital and acquired changes within the inner ear. Congenital defects in the meatus acusticus internus, the endolymphatic duct and sac, the cochlea and the vestibulum can be diagnosed and also quantified. Infectious morphologic changes can be seen on CT images in their terminal residual state (sclerotic tissue). However, acute inflammation and fibrotic tissue is not visible on CT. T2-specific MRT images are very fluid sensitive and play a major role in preoperative cochlear implant diagnosis. This examination demonstrates fluid within the peri- and enolymphatic cave and permits the diagnostician to determine whether congenital or acquired diseases have destroyed such fluid-filled cavities. In order to demonstrate pathological changes in the temporal bone and neural structures in the inner ear, MRT is the preferred method. Displaying the modiolus and the cochlear nerve is extremely important because, in their absence, a cochlear implantation may be contra-indicated. MRT also demonstrates other neural structures such as the facial nerve. This information may be important for the surgeon, e.g. the state of the pneumatic system in the mastoid cavity (which is best visualised by bone-specific CT).

[Speech discrimination in post-lingually deaf patients with cochlear implants]. / Sprachdiskrimination bei postlingual ertaubten, Cochlear-implantierten Patienten.

The aim of this study was to measure the speech discrimination performance of postlingually deaf patients using the Combi 40/40+ cochlear implant (Med-El, Innsbruck). The speech perception performance of 37 adults was tested over a time span of three years. We used a standardised test battery comprising number, monosyllable, sentence, consonant and vowel discrimination tests. Testing was performed immediately after initial fitting and 1, 3, 5, 12, 24, and 36 months thereafter. The average correct answers for all tests were as follows: right after the implantation 29.1%, after 1 month 46.7%, after 3 months 53.9% after 1 year 63.5% and after 3 years 68.5%. Some patients reached a number discrimination rate of 100%. The discrimination for monosyllables averaged 41.1% two years after implantation. The results demonstrated continuous improvement of speech perception, even after three years following implantation.

[Hearing and speech discrimination scores of prelingually deaf children with cochlear implants]. / Hör- und Sprachdiskriminationsleistungen prälingual ertaubter Cochlear-implantierter Kinder.

The goal of this study is to report mean values of speech perception performance in prelingually deaf children who received a Combi 40/40+ cochlear implant. Thirty-one patients were included in the study. The time span ranged over 3 years, during which time the Evaluation of Auditory Responses to Speech (EARS) test battery was used in the children. The EARS battery contains 4 measures of closed-set speech perception and 3 open-set tests. The mean test results exhibited steady improvement in all parts of the EARS test battery, even up to 3 years post-implantation. The mean preoperative scores were 0.3%, increasing to 92.3% at 36 months post-implantation for the best children. Results for the closed-set testing measures were most encouraging, with some children reaching fairly high levels of speech perception and achieving scores as high as 98.7% at the 36-month evaluation. The congenitally and prelingually deaf children in our study showed continuous improvement in both closed and open set speech perception following cochlear implantation, although individual variations in performance were noted.

[Speech discrimination in noise for patients with cochlear implants]. / Sprachdiskrimination im Störschall bei Cochlear-implantierten Patienten.

The aim of the study was to evaluate the speech discrimination ability of postlingually deaf adults implanted with the Combi 40 cochlear implant in noise and to compare the results with the speech discrimination ability of patients provided with hearing aids. The 12-month postoperative hearing performance of 12 consecutive patients was tested using a sentence discrimination test in quiet and noise. The results of the present study demonstrate that all patients obtained substantial benefit from their implants even in situations coupled with noise. The speech understanding of cochlea-implanted patients appears to be better than that of patients provided with hearing aids. Very high scores (mean, 40.2%) were achieved at a signal-noise ratio of 15 dB.

[Preoperative diagnostic procedures before cochlear implantation]. / Präoperative Diagnostik vor einer Cochlear-Implantation.

About 200 patients are considered each year for cochlear implant recipiency. Only 1/4 of these candidates actually receive an implant. The aim of the study is to discuss the preoperative procedure we use, which is aimed to exclude patients who would not benefit from an implant. A cochlear implant is an example of very expensive high-profile medical therapy, a single implant costing about 280,000 Austrian schillings. The aim of the preoperative diagnostic procedure is to select the right patients, with a view to providing the best audiologic outcome. During the past 20 years, important parameters have been identified to determine suitable patients. Candidates for a cochlear implant are infants and children (independent of the etiology of deafness or high-grade hearing loss), as well as postlingual deaf adults. Congenitally deaf adults or teenagers are considered unsuitable to receive an implant.

[Postoperative imaging and evaluation of the electrode position and depth of insertion of multichannel cochlear implants by means of high-resolution computed tomography and conventional X-rays]. / Postoperative Darstellung und Erfassung der Lage und Insertionstiefe von multikanalikulären Cochlear-Implantaten durch die hochauflösende Computertomographie und durch das Nativröntgen.

Following cochlear implantation, postoperative imaging of the electrode is very important in order to measure the depth of insertion and the position of the electrode, so that kinking and incorrect electrode placement can be clearly identified. The aim of this study was to outline the diagnostic value of CT and conventional X-ray for these parameters. For this purpose we obtained radiographs of patients who had received a cochlear implant. Computed tomography was performed by obtaining axial sections. For conventional X-ray we used digital imaging, utilising a modified Chausse III projection. The images were then rated according to electrode position, insertion depth and possible complications. We also measured the radiation dose using a dummy and evaluated the cost of each examination. Both examinations permit excellent identification of electrode position and insertion depth. However, the depth of insertion can be measured much more accurately by means of digital X-ray. The radiation dose of CT was 230 times higher than that of conventional X-ray and the cost of CT 5 times that of digital X-ray.

[Clinical utilization of magnetic resonance imaging for patients with cochlear implants]. / Klinische Anwendung von Magnetresonanztomographie bei Cochlear-implantierten Patienten.

To date, MR imaging is absolutely contraindicated in cochlear-implanted patients. The aim of this study is to document the potential value of MR imaging in such patients, without injurious or side effects and without technical device failure. After in vitro experimental testing, 25 cochlear implanted patients underwent MRI. Radiological evaluation was also possible. The use of 1-Tesla fast spin echo sequences minimised artifacts. All cochlear implants are still in working order; no changes in fitting data or a reduction in speech understanding were observed. MR helped to avoid other invasive medical procedures.