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I J Hochmair-Desoyer

Publications and source records attributed to I J Hochmair-Desoyer.

At least 19 recordsLinked to original sources
PubMed1999

Magnetic resonance imaging and cochlear implants: compatibility and safety aspects.

With cochlear implants, magnetic resonance imaging (MRI) has until recently been contraindicated due to excessive magnetic and electromagnetic interference. The aim of this study was to determine the MRI compatibility of the Med-E1 Combi 40/40+ cochlear implant, within a wide range of clinical MRI applications. In vitro experiments on a 1.5 T MR scanner were performed. Torque, force, demagnetization, artifacts, induced voltages, and temperature increase were measured in worst case scenarios for the implant. In addition, stabilization experiments were performed. It was shown that most of the electromagnetic interferences between the cochlear implant and the 1.5 T scanner remained within acceptable limits. One exception is the torque on the internal magnet, which represents a hazard for patients with these cochlear implants. Therefore, MRI examination should only be performed if there is a strong medical indication, and certainly some assessment of the relative risks involved versus the risk of not providing the diagnostic capabilities of MRI, will have to be made. Appropriate safety measures should be taken.

Artifacts↗
PubMed1998

Cochlear implants: in vitro investigation of electromagnetic interference at MR imaging--compatibility and safety aspects.

In vitro experiments were performed to determine the compatibility of a cochlear implant at 0.2- and 1.5-T magnetic resonance (MR) imaging. Except for the torque at 1.5 T, all electromagnetic interferences remained within acceptable limits. MR imaging should be performed only if there is a strong medical indication, by following appropriate safety procedures. MR imaging at 0.2 T should be safe; at 1.5 T, however, the relative risks will have to be assessed.

Cochlear Implants↗
PubMed1997

A bone-anchored percutaneous connector system for neural prosthetic applications.

A percutaneous connector system has been developed for use in neural prosthetic applications. It is based on a skin-penetrating, bone-anchored titanium pedestal, housing an II-channel electrode array. Initial applications for the system are in audiology and as such, the proposed fixture site is in the temporal bone. The titanium pedestal is based on existing design features of the EPI Bioglass implant, developed by University College London (UCL), and the Brånemark System, employed by Nobel Biocare AB. The electrode array, consisting of platinum wires in a silicone carrier, can be custom designed to suit the application. The design features of the connector system are reviewed. Animal studies have been used to assess soft tissue reactions and the osseointegration of the pedestal. The histological data are presented. The pedestal, electrode array and the mating external connector are currently undergoing mechanical and electrical testing. The percutaneous connector system will undergo clinical trials, initially in the study of tinnitus (employing stimulation via an extracochlear electrode), and as part of a cochlear implant system (using a multichannel intracochlear electrode array and digital signal processing techniques.

Animals↗
PubMed1993

New hardware for analog and combined analog and pulsatile sound-encoding strategies.

Development for cochlear implants of primarily analog design focuses in two directions. The first direction is miniaturization. A behind-the-ear (BTE) speech processor has been developed which can replace the body-worn processor for approximately 90% of the users of a MED-EL cochlear implant and works with two 1.4 V hearing aid batteries for between seven and twelve days. Consonant, vowel and sentence testing and patient questioning revealed that the BTE speech processor demonstrates a significant improvement in speech understanding compared to the body-worn processor, and that the patients' device acceptance is superior for the BTE processor. The result of the second direction for our cochlear implant development is the multichannel cochlear implant, CAP, with combined analog and pulsatile stimulation. It aims at complementing the information from the broad-band analog signal by adding spectral information, that is, tonotopic information. This device is capable of simultaneously stimulating one electrode channel with a broad-band analog signal and one of eight electrode channels with a pulsatile signal. The system can also be used for purely analog or for purely pulsatile stimulation. Preliminary results with the first recipient of a CAP cochlear implant system demonstrate that the device works as expected.

Acoustic Stimulation↗
PubMed1990

Initial results with simultaneous analog and pulsatile stimulation of the cochlea.

An improved method has been developed for the coding of speech information into adequate signals for the stimulation of the auditory nerve. It combines the periodicity principle, which has been applied in single-channel analog stimulation in the Austrian cochlear prosthesis, with the place principle by simultaneous analog stimulation on one channel and pulsatile stimulation on other channels. The second formant frequency determines the place of stimulation for the pulsatile signals. Simultaneous stimulation of several channels can cause the currents emerging from different electrodes to interact because the fluid impedance in the cochlea is small. Therefore, an important aspect of the multichannel strategy is to maintain the temporal pattern transmitted via the analog channel by adequate repetition rates and phase relationships of the pulsatile signals. The signals were processed with finite impulse response digital filters. Vowel identification tests were performed with 6 patients implanted with a 4-channel intracochlear electrode. The test material was spoken by male and female speakers. With proper timing of the pulses the improvement over the single-channel stimulation was significant at the 1% level and this difference was due to a significant increase in second formant recognition.

Cochlear Implants↗
PubMed1986

Fitting of an analogue cochlear prosthesis--introduction of a new method and preliminary findings.

A new method is suggested for the fitting of a broad-band analogue cochlear prosthesis in terms of frequency response adjustment. This 'frequency-stepped sweep' (FSS) method employs a feedback loop including the patient's loudness judgement to determine a frequency response for the patient's sound processor with which a continuous sinusoidal stimulus with constant amplitude and small increments in frequency can be heard equally loud at the most comfortable loudness level. The FSS-method has been successfully used for the fitting of the sound processors of 40 cochlear implant users. An evaluation of the FSS-method through speech tests employing five different frequency response adjustments with two implant patients confirms its appropriateness. The importance of proper fitting in terms of the frequency response adjustment for a cochlear prosthesis based on broad-band analogue stimulation is demonstrated. The necessary accuracy for the frequency response adjustment is approximately +/- 2 to +/- 5 dB (depending on the dynamic range of the patient) over the frequency range between 100 and 3000 Hz. For the proper adjustments no significant difference has been found between the results for a male and a female speaker.

Acoustic Stimulation↗
PubMed1986

The Vienna cochlear implant program.

The cochlear implant program in Vienna has now gathered 160 patient years of experience with 25 patients who have received an extracochlear implant prosthesis and 31 patients who have received an intracochlear implant prosthesis. The sound processor avoids the transformation of speech into pulses and provides a processed analog broad-band stimulation signal. Approximately one half of the patients are prelingually deaf. The selection criteria include electrical promontory stimulation and acoustic and electrical brain-stem audiometry. The rehabilitation program consisting of counseling, communication training, and auditory training is considered an important part of the program. The results are assessed using the Vienna Auditory Test battery. Sixty per cent of the postlingually deafened patients achieve some open-set speech understanding without lip-reading. Sixty-five per cent of the users show a substantial improvement in aided speech understanding versus lip-reading alone.

Audiometry, Evoked Response↗
PubMed1984

A model for the electrostimulation of the nervus acusticus.

Electrostimulation of the nervus acusticus has been successfully used to achieve speech understanding. A model of nerve excitation due to Fitzhugh [(1961) Biophys. J. 1, 445-446] has been explored to show that the stochastic response of single acoustic mammalian fibers observed by Rose, Brugge, Anderson and Hind [(1967) J. Neurophysiol. 30, 769-793] may be due to the non-linear interaction of sub-threshold electrical nerve activity with the signal. Computations by means of an analogue computer also shows that a phase-locked response with a frequency dependence resembling behaviour observed with electrostimulation is obtained with the model. A dynamic range for single fiber excitation is produced by the non-linear interaction.

Cochlear Implants↗
PubMed1983

Percepts from the Vienna cochlear prosthesis.

This report includes psychophysical data on some of the 13 patients who have been equipped with intracochlear electrodes and the 6 patients who have received an extracochlear electrode. Thresholds and uncomfortable listening levels versus frequency, amplitude difference limens, and gap detection in noise and frequency difference limens have been determined and represent some essential characteristics of prosthetic hearing.

Adolescent↗
PubMed1981

Four years of experience with cochlear prostheses.

Within the last four years, clinical as well as engineering experience has been gathered with 12 deaf persons who received several versions of an auditory prosthesis. Two years ago we settled on a system consisting of a versatile, passive 4-channel implant driving a scala tympani electrode, and a small external speech-processor. The main characteristics of the prosthetic hearing which can thus be established are: dynamic ranges vary between 12 and 20 dB, the number of discriminable amplitude steps within the dynamic range is comparable to that of a normal-hearing person; subjective pitch increases with stimulation frequency up to at least 1,000 Hz. Thresholds and dynamic ranges as well as a number of other characteristics remain stable over long periods of time. After an initial big step to good open speech understanding by one of our patients it could now be shown, that this patient is not an exemption. Several deaf patients participating in a series of speech tests have demonstrated that it is possible to reestablish some understanding of open speech through the use of the cochlear prosthesis without additional lipreading. A program has been established which aims at achieving experience with this prosthesis in a larger number of deaf people. The program includes: implant candidate selection, implantation, adjustment of speech-processor, hearing and speech rehabilitation, and the collection of comparative "psychoelectric" characteristics.

Adolescent↗
PubMed1980

Cochlear prostheses in use: recent speech comprehension results.

Speech-comprehension tests were performed with several deaf volunteers who were equipped with different cochlear prostheses. These prostheses work with inductive transcutaneous signal transmission and contain a multi-channel scala tympani electrode or, in two cases, a disc electrode situated external to the cochlea in the round window niche. The external portable single-channel speech-processor/transmitter used is the same in all cases. The comprehension (stimulation only, no lip reading) of numbers between 1 and 99 on first contact with the stimulator and therefore without any training was around 38% showing that through well designed single-channel stimulation of the auditory nerve it is possible to generate hearing sensations sounding very much like nature hearing impressions. Some open speech comprehension was reached: Through the help of the stimulator, without lip reading, between 60 and 100% of sentences unknown to the completely deaf volunteer, spoken only a little more slowly than normal, are correctly understood. The percentage for isolated unknown words is 60%. Also an important improvement of word comprehension can be achieved through additional stimulation as compared to unaided lip reading. It appears that the most recent design of our cochlear prosthesis can already be regarded as a useful aid for the deaf.

Adult↗
PubMed1979

Investigations towards an artificial cochlea.

Two versions of multichannel cochlear stimulators have been implanted, one allowing stimulation against a common distributed ground within the cochlea and the other allowing bipolar stimulation. The results obtained indicate that with both versions sufficiently discrete stimulation of the auditory nerve is possible in order to be able to make use of tonotopy for the processing of speech. The bipolar stimulation, however, besides of being characterized by higher thresholds than unipolar stimulation, also leads to a very narrow range of stimulus frequency within which perceived pitch is influenced by stimulus frequency. Surprisingly different psychophysical behaviours are exhibited by the two subjects considered, one being a case of prelingual, the other of acquired deafness. This indicates the marked influence which etiology of deafness might have on design considerations for auditory prostheses.

Acoustic Stimulation↗
PubMedDate not supplied

[Status of the development of cochlear prostheses relying on electric stimulation].

Inner ear prostheses, or cochlear implants, are neuroprostheses providing profoundly deaf people with sound sensations through electrical stimulation of the auditory nerve. Approximately 2,000 of these devices are currently in use worldwide. Five models are each being used by more than 50 patients. Among other features they differ from one another mainly in the design and placement of electrodes and in the particular speech coding strategy used, periodicity and tonotopy priciple being made use of to a highly varying degree. Nevertheless, 4 of the 5 devices lead to quite comparable degrees of speech understanding without additional lipreading.

Cochlear Implants↗