Biomedical subjects
Publications and source records attributed to K Burian.
Under the observance of a few selection criteria electrostimulation of the cochlea nerve with cochlea implants is a suitable method to supply totally deafs with a hearing ability and in about the half of the patients even with speech understanding. The technology of the Vienna Cochlea Implant, selection criteria, surgical technique as well as the rehabilitation procedure and the results are discussed.
Selection criteria, basic principles of auditory training, development of an auditory test battery for children and results of 15 children between 4 and 14 years are presented and discussed. To summarize, results range from acoustic attention to tones and sounds and recognition of environmental sounds to the use of supra-segmental and segmental features of speech. Some children are able to recognize words and phrases from a closed list. One of the children has postlingual deafness and has had also a very short duration of deafness before implantation. This child shows better results than the pre and perilingually deaf children. Because of the fact that the patient group is small and there are also many intervening variables like age, duration of deafness and use of two different test instruments, it is difficult to find a relationship between the results and all other variables. The auditory test battery for children, which consists of seven subtests, measuring acoustic orientation and auditory speech perception on different linguistic levels, is much more suitable for the evaluation of auditory performance for this age group than the auditory test battery for adults (Eisenwort and Burian 1988).
A behind the ear-wearable speech processor for the Vienna cochlear prosthesis has been designed. In a comparative study 6 patients used the new device for 1 week and were then tested. The results from the auditory test battery and a speech tracking were about the same, only the perception of speech from an open list was better when the patients used the conventional processor. It is possible to reduce the size of a speech processor substantially by modifying the speech-processing strategy without major decrease of the performance. More patients have to be tested after using the device for a longer time.
The Auditory Test Battery for children, a test instrument for the German language, which measures acoustic orientation and speech perception on different linguistic levels, is described. Speech perception data for each subject, gathered from 8 implanted children, are presented.
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In a study on 36 cochlear implant patients questionnaires answered pre- and postsurgically were analyzed. One year after implantation patients demonstrated significant changes on some of the test items. Although results show that the patients accept their device, some of their wishes and hopes remain unsatisfied.
Open set speech comprehension can be achieved by intra- and extracochlear stimulation using an analog broadband signal. There is a tendency that intracochlear provided patients achieve better scores for open set speech comprehension than extracochlear implanted patients. Four prelingually deaf children acquired awareness of tones and sounds and some of them are able to use suprasegmental cues. After reimplantation, speech comprehension scores remain stable. For three patients scores even improve. Controls of the pure-tone audiograms demonstrate that extracochlear implants do not destroy residual hearing.
The common selection criteria for cochlear implant patients do not allow any prognostic indication on the final result. On the other hand, some postoperative data (threshold, TDL, dynamic range, duration of deafness) corresponds clearly with the results, some of them also correspond with the preoperative data. Preoperative TDL, dynamic range as well as duration of deafness can therefore be used as suitable prognostic indicators.
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Pre- and post-surgical treatment of cochlear implant patients is discussed. Before surgery training of lipreading ability, auditory training with conventional hearing aids and counselling should be offered. After surgery the main focus lies on auditory training with the cochlear implant; communication training in a group and counselling should be offered too.
UNLABELLED: Mechanical ventilation in the neonatal period is sometimes followed by difficulty in removal of the endotracheal tube although the patient does not need further respiratory support. This problem results from subglottic stenosis consequent on prolonged use of endotracheal tubes. We found this complication in 5 patients among 854 newborns who required artificial respiration. A further patient was admitted from another hospital because of extubation problems. Our clinical diagnosis was confirmed by endoscopy. Drug therapy with steroids and anti-inflammatory agents was tried in all six patients and was successful in two. In four patients conservative management failed and laser surgery was performed; three of these infants required tracheostomy. In two decannulation has already been performed at the age of 2 1/2 years. IN CONCLUSION: five of six patients were treated successfully, and one 3-year-old patient is still being treated. In the light of reports from other authors, this approach can be recommended for the management of acquired subglottic stenosis.
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Basing on the results obtained with 63 patients stimulated via the extracochlear or intracochlear version of the Vienna Cochlea Implant the following topics are discussed: Extracochlear versus intracochlear stimulation. Cochlea Implants in small children. Preoperative signs regarding the final result. Ideas for evaluation of results. Extracochlear or intracochlear stimulation enables speech understanding in about one-half of the postlingual deaf patients but the extent of speech recognition is greater when intracochlearly stimulated. Long-term follow-up as well as our experience with patients who had to be reimplanted demonstrate that the implantation manoevre does not create clinically relevant signs of damage. After the experiences with cochlear implants in adults their use in small children was encouraged, the more so since electric stimulation of prelingual deaf adults does not mediate speech recognition. There seems to be a chance to achieve speech comprehension if electric stimulation starts very early. The age limit in our group is the end of the third year. Final results cannot be presented but it is very clear that acoustic orientation and verbalisation are created and enhanced by electric stimulation. With regard to the preoperative prognosis, three parameters (threshold, dynamic range and TDL) are valid, of which TDL seems to be of major importance. The evaluation of the results should follow the hierarchical organisation of the language and must consider the three main levels of speech organisation.
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.
Insertion of intracochlear electrodes may damage the basilar membrane, the stria vascularis and adjacent structures. When electrodes were placed in human temporal bone specimens, perforations were shown to be independent of the type of implant used, the depth of insertion or the use of a lubricating agent. Helical electrode reinforcements and failure to enlarge the round window frame increase the risk of damage. Perforations are invariably localized at a distance of about 7-14 mm from the round window and occur at the site where the curvature of the basal turn is greatest.
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For 20 years direct electrical stimulation has been used in cases of severe bilateral hearing loss or complete deafness to mediate acoustic percepts. The relevant literature is reviewed. While these attempts were initially thought to be unphysiological and unsuited for transferring speech, acoustic sensations were successfully conveyed even with the very simple unichannel electrodes through percutaneous signal transfer. Patients fitted with such simple systems were able to hear and distinguish environmental noise and speech, their lip reading as well as their speech improved. Speech discrimination was, however, impossible with such simple implants both on theoretical grounds and in practical terms, because frequency analysis is exclusively based on periodicity (up to 400 Hz). Designing bipolar multichannel electrodes which, when introduced into the scala tympani or the modiolus, produce discrete stimulation of several circumscribed groups of nerve fibers, was the logical consequence of earlier attempts along these lines, Implantation of these systems can be done along the transmeatal, meato-mastoidal or mastoidal approach. The electrodes can be implanted in bundles through the round window or into the modiolus; they can, however, also be introduced individually through several drill holes in the promontory for placement in the scala tympani and vestibuli. This produces a far more differentiated stimulation simulating a tonotopic pattern of stimuli. In addition to periodicity, the place principle can thus be utilized for frequency coding. While their dynamic range is rather poor (15 to 30 dB at best), multichannel systems, in theory, offer substantially more favorable conditions for speech intelligibility. Since current knowledge of speech coding is, however, inadequate, the degree of intelligibility obtainable is still insufficient for everyday life. Inspite of this flaw, such implants as are available today substantially benefit the patients, who are able to establish acoustic communications with their environment by distinguishing environmental noise from speech, to discriminate between male and female voices, to recognize musical rhythms and even to understand a few words. Indications for the implantation of prostheses, the requisite conditions and postoperative training programs are discussed. While cochlear implants are still experimental, they appear to be reasonably justified in selected cases, since they have been well tolerated by all patients treated sofar without causing any complications and since many of the data obtainable can only be collected in humans. It is, however, essential that experimental implantation be exclusively dealt with by specialized teams, which should evaluate such data as are available and translate them into practice as soon as possible. A routine impantation of hearing prostheses is currently unwarranted.
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