Biomedical subjects

M Vischer

Publications and source records attributed to M Vischer.

6 recordsLinked to original sources

PubMed2004

[The cochlear implant--evolution of hearing and language with an artificial inner ear].

One of the most spectacular progresses in modern medicine is the possibility to replace a deaf ear, a sensory organ in total by an implantable electronic prosthesis, a so-called cochlear implant (CI). The CI stimulates the auditory nerve by electrical pulses and thus generates the sensation of hearing along the auditory pathway. One of the most impressive aspects of cochlear implantation is the fact that small children with profound deafness who were able a few years ago to learn spoken language only to very limited extent may achieve nowadays an almost normal language development. Duration and intensity of the training of listening and spoken language vary considerably as a function of etiology and time of deafness. Most important for the development of language is sufficient stimulation of the auditory pathway during early childhood. Early diagnosis of a severe to profound deafness is most important in order to fit hearing aids or a cochlear implant without a time delay. Affected children need intensive training by professionals specialized in education and speech therapy. Adults and adolescents who lost their hearing when language acquisition was established may understand spoken language only a few weeks after receiving a cochlear implant. Several individuals are able to use the telephone. Preliminary results after bilateral cochlear implantation of children and adults show advantages. Not only do these subjects report "better hearing with two CI as compared to hearing with one CI," but some of them developed directional hearing in a rather short time lag after fitting the second implant. And in addition they achieve better speech discrimination in environmental noise.

Adolescent↗

PubMed2001

Vestibular function in patients with cochlear implantation.

The aim of this work was to determine the influence of cochlear implantation (CI) on vestibular canal and otolithic function. Between 1995 and 1999, 15 patients (6 females, 9 males; 9-77 years old) underwent a vestibular examination before and after CI. Electronystagmography was performed between 5 and 8 days after CI in 9 patients, and with a time delay of 2-24 months in 10 patients. Pre- and postoperative evaluation included electronystagmography with caloric (44 degrees C, 30 degrees C, ice-water) and pendular rotatory testing. Otolithic function was measured postoperatively using off-vertical axis rotation (OVAR) in six patients. Preoperative data (n = 14) showed areflexia on caloric and rotatory pendular testing in deafness cases due to meningitis (n = 2) and in 2/5 patients with sudden idiopathic bilateral deafness. Two patients suffering from an idiopathic deafness had a unilateral hyporeflexia. Vestibular function was normal in the other eight patients. Immediately following CI, among patients with normal preoperative canal function, three developed vertiginous symptoms with spontaneous nystagmus, which disappeared within days to weeks. Later, postoperative canal evaluation was normal in 5/8 patients (62%) with initially preserved vestibular function: areflexia was measured ipsilaterally to the implanted ear in 1 patient and contralaterally in 2 patients. Hyporeflexia was measured ipsilateral to the implanted ear in two patients. OVAR examination, performed 2-19 months after surgery, showed a preserved otolithic function in all 6 tested patients. Transient vertigo on electrical CI stimulation was described in only one patient during the first postoperative weeks. The following conclusions can be drawn. Patients with deafness due to meningitis had an eradicated vestibular function. In other etiologies, vestibular function was most often preserved. CI did not usually abolish vestibular function, but the canal function was disturbed temporarily in 20% of cases. Otolithic function was preserved in all six CI patients tested in this series.

Adolescent↗

PubMed2000

[First results of a national hearing screening program in Switzerlans].

A Swiss study group was formed in summer 1998 with the aim of establishing a universal hearing screening programme in newborns following the recommendations of the "European Consensus Statement on Neonatal Hearing Screening" (Milan 1998). The aim of the group was to standardise and to introduce universal hearing screening in all infants born in Switzerland. Starting in June 1999, several hospitals in Switzerland began the screening programme using commercially available equipment for easy and highly automated measurement of transient evoked otoacoustic emissions. Up to March 2000, 6262 children were born in these hospitals and 5656 (90%) underwent neonatal hearing screening. 88 children of the 5656 did not pass the screening test. The measurement of otoacoustic emissions was repeated in a follow-up examination within 6 weeks. If otoacoustic emissions were again absent, evoked auditory brainstem potentials were measured. 48 children were found to have hearing within normal limits at the follow-up examination, 24 children have not been examined yet, 11 children were examined in other clinics or the follow-up examination was refused by the parents. 5 children were found to have bilateral hearing dysfunction and were referred to rehabilitation within the first 6 months of life.

Evoked Potentials, Auditory, Brain Stem↗

PubMed1997

Effect of high-frequency electrical stimulation of the auditory nerve in an animal model of cochlear implants.

HYPOTHESIS: Electrical stimulation of the cochlea at high rates induces significant adaptation of the auditory nerve. BACKGROUND: A new development of cochlear implants is the use of speech processors delivering electrical pulses on the implanted electrodes at high rates, such as 1,000 pulses per second (pps) and above. Such a stimulation mode allows subjects with cochlear implants to reach excellent understanding of speech. METHODS: Long Evans-rats received implantation of stimulating electrodes in the left cochlea. Two hundred-millisecond trains of short (20 microns) monophasic pulses were delivered in 50% duty cycle at 500 microA above threshold. The pulse rate in the train was increased from 100 pps to 1,500 pps. Electrically evoked auditory brainstem responses (EABR) were recorded. The amplitude of the compound action potential of the auditory nerve to each single pulse in the train was measured as the first vertex positive wave (WAVE I) of the EABR. RESULTS: At 100 and 200 pps, WAVE I amplitudes to each pulse were large and remained stable throughout the pulse train. For increasing pulse rates, WAVE I amplitudes progressively decreased during the first 40 to 50 ms of the train and reached 80% at 300 pps to 15% at 1,500 pps of the maximal amplitude observed for the first pulse in the train. CONCLUSIONS: The decrease of the WAVE I amplitude in response to high-rate pulsatile stimulation reflects an adaptation of the auditory nerve due, at least in part, to the refractory period of auditory nerve fibers.

Acoustic Stimulation↗

PubMed1996

[Tracheobronchial foreign body in children. Is anamnesis alone enough to indicate tracheobronchoscopy?].

From 1989-1993 we performed rigid bronchoscopies in 86 children in whom foreign body aspirations were suspected. In 72 cases, foreign bodies were identified in the tracheobronchial tree. In the remaining 14, no foreign body was found. Boys outnumbered girls. The most common type of foreign body was a peanut. The predilection of the foreign body was to fall into the right main bronchus. If the history indicated foreign body aspiration, a chest x-ray was not found to be necessary except for forensic interest.

Bronchi↗

PubMedDate not supplied

Comparison of the TEMPO+ ear-level speech processor and the cis pro+ body-worn processor in adult MED-EL cochlear implant users.

A study was conducted to compare the new MED-EL TEMPO+ ear-level speech processor with the CIS PRO+ body-worn processor in the COMBI 40/COMBI 40+ implant system. Speech tests were performed in 46 experienced subjects in two test sessions approximately 4 weeks apart. Subjects were switched over from the CIS PRO+ to the TEMPO+ in the first session and used only the TEMPO+ in the time between the two sessions. Speech tests included monosyllabic word tests and sentence tests via the telephone. An adaptive noise method was used to adjust each subject's scores to approximately 50%. Additionally, subjects had to complete a questionnaire based on their 4 weeks of experience with the TEMPO+. The speech test results showed a statistically significant improvement in the monosyllabic word scores with the TEMPO+. In addition, in the second session, subjects showed a significant improvement when using the telephone with the TEMPO+, indicating some learning in this task. In the questionnaire, the vast majority of subjects found that the TEMPO+ allows equal or better speech understanding and rated the sound quality of the TEMPO+ higher. All these objective and subjective results indicate the superiority of the TEMPO+ and are mainly attributed to a new coding strategy called CIS+ and its implementation in the TEMPO+. In other words, based on the results of this study, it appears that after switching over from the CIS PRO+ to the TEMPO+, subjects are able to maintain or even improve their own speech understanding capability.

Adult↗