Biomedical subjects

Uwe Baumann

Publications and source records attributed to Uwe Baumann.

6 recordsLinked to original sources

PubMed2006

The cochlear implant electrode-pitch function.

The cochlear frequency-place function in normal hearing ears has been found to be an exponential relationship in a wide variety of species [D.D. Greenwood, J. Acoust. Soc. Am. 87 (1990) 2592-2605]. Although it seems reasonable to assume a similar function for electrical stimulation by means of an intra-cochlear electrode array, the exact frequency-place function for this special type of stimulation needs to be investigated. Six users of the MED-EL COMBI 40+ cochlear implant device with moderate to profound hearing loss between 125 and 1000 Hz in the non-implanted ear took part in a binaural pitch adjustment experiment. The COMBI 40+ electrode array provides a deep insertion into the scala tympani and a wide spatial separation between the stimulating electrodes. Insertion depth was controlled by Stenver's view plain radiographs and the insertion angle was estimated. The task of the subjects was to adjust the frequency of a sinusoid presented in the non-implanted ear by means of an adjusting knob until they perceived the same pitch as was elicited by a reference stimulus in the implanted ear. The results show adjustments corresponding to electrode positions along the cochlea, with the exception of the two most apical electrodes for most of the subjects. Pitch increased in an orderly fashion with an average of 98 Hz per electrode separation (40 Hz/mm). In contrast to the exponential predictions according to [D.D. Greenwood, J. Acoust. Soc. Am. 87 (1990) 2592-2605] for normal hearing, the average electrode-pitch function shows a linear relationship.

Adult↗

PubMed2004

Pulse rate discrimination with deeply inserted electrode arrays.

Pulse rate difference limen (PRDL) and amplitude modulation difference limen (AMDL) were assessed as a function of base rate and cochlear electrode location in seven (three for AMDL) subjects implanted with the MED-EL COMBI 40+ implant. The MED-EL COMBI 40+ electrode array allows deep insertion of the electrode up to the apex of the cochlea to minimize the rate/place mismatch for pulse rates below 500 pps. A three interval, two alternative forced-choice procedure with feedback was used to measure the difference limen. The base rate was in the range between 200 and 800 pps. The carrier rate for the AMDL measurement was 5081 pps. The PRDL increased with increasing base pulse rate. At 200 pps the average PRDL measured at the apical electrode amounted to 48.7 pps, at 400 pps the average PRDL reached 206.6 pps. No significant difference between PRDL obtained from apical or basal electrodes could be observed. AMDL was higher than PRDL at all tested base rates. The ability to discriminate rate changes is limited to base rates up to about 283 pps. The results indicate that rate changes smaller than a major third do not elicit distinguishable auditory perceptions in electrical hearing. The absence of a difference between apical and basal electrode locations indicates that a reduction of the rate/place mismatch does not improve discrimination performance.

Adult↗

PubMed2004

Pitch ranking with deeply inserted electrode arrays.

OBJECTIVE: Electrode pitch ranking was assessed as a function of cochlear region, electrode spacing, and stimulation rate in eight subjects implanted with the MED-EL COMBI 40+ implant. The MED-EL COMBI 40+ electrode array allows deep insertion of the electrode up to the apex of the cochlea and provides a wide electrode spacing of 2.4 mm. DESIGN: The pitch of a reference electrode was compared with the pitch of two apical and two basal probe electrodes using a two-alternative forced-choice procedure. The reference electrodes were placed in the apical region, in the middle region, and in the basal region of the cochlea. Each condition was tested at pulse rates of 1515 pps, 500 pps, and 250 pps. RESULTS: Electrode pitch ranking did not depend on electrode spacing, the position of the reference electrode in the cochlea, or stimulation rate. CONCLUSIONS: These results indicate that a spacing of 2.4 mm seems sufficient to allow good electrode pitch ranking performance for the average user and that electrode pitch ranking is similar in the apical, middle, and basal region of the cochlea, irrespective of the stimulation rate. Most importantly, the results of this study indicate that residual neural structures in the apical region of the cochlea are sensitive to pitch changes provided by different places of electrical stimulation.

Adult↗

PubMed2004

Labyrinth dysfunction 8 months after cochlear implantation: a case report.

OBJECTIVE: Investigate whether the cochleostomy is a possible port of entry for pneumolabyrinth and a resulting vertigo in patients provided with a cochlear implant. STUDY DESIGN: Retrospective case review. SETTING: Ludwig-Maximilians University of Munich, Hospital Grosshadern. PATIENT: 62-year-old patient who underwent implantation of a HiFocus II cochlear implant with positioner from Advanced Bionics (CLARION). Eight months postoperatively, the patient reported rotatory vertigo and right-side tinnitus after he had blown his nose harder than usual during an episode of rhinitis. INTERVENTIONS: Preoperative and postoperative testing of both the petrosal bone with a CT scan and of balance function. MAIN OUTCOME MEASURE: Air inclusion in the labyrinth. RESULTS: In contrast to the preoperative high resolution computed tomography (CT) scan, air inclusion was seen in the labyrinth during the episode of vertigo. At the same time, balance function tests with Frenzel glasses revealed both spontaneous and provoked horizontal nystagmus to the right side. At follow-up 8 weeks later, the level of vertigo had significantly decreased. Twelve months later, the control CT showed the cochlear implant positioned correctly and no visible air in the labyrinth. CONCLUSION: It is known that placement of the HiFocus II with Positioner from CLARION requires a relatively large cochleostomy of 1.5 mm. Moreover, in the connective tissue seal between the electrode and the positioner, the latter reaches into the tympanic cavity, and this is possibly the weak point. Further investigation will be needed to determine whether the large cochleostomy with the HiFocus II with positioner increases the predisposition to labyrinth dysfunction.

Cochlear Implantation↗

PubMed2004

Localization ability with bimodal hearing aids and bilateral cochlear implants.

After successful cochlear implantation in one ear, some patients continue to use a hearing aid at the contralateral ear. They report an improved reception of speech, especially in noise, as well as a better perception of music when the hearing aid and cochlear implant are used in this bimodal combination. Some individuals in this bimodal patient group also report the impression of an improved localization ability. Similar experiences are reported by the group of bilateral cochlear implantees. In this study, a survey of 11 bimodally and 4 bilaterally equipped cochlear implant users was carried out to assess localization ability. Individuals in the bimodal implant group were all provided with the same type of hearing aid in the opposite ear, and subjects in the bilateral implant group used cochlear implants of the same manufacturer on each ear. Subjects adjusted the spot of a computer-controlled laser-pointer to the perceived direction of sound incidence in the frontal horizontal plane by rotating a trackball. Two subjects of the bimodal group who had substantial residual hearing showed localization ability in the bimodal configuration, whereas using each single device only the subject with better residual hearing was able to discriminate the side of sound origin. Five other subjects with more pronounced hearing loss displayed an ability for side discrimination through the use of bimodal aids, while four of them were already able to discriminate the side with a single device. Of the bilateral cochlear implant group one subject showed localization accuracy close to that of normal hearing subjects. This subject was also able to discriminate the side of sound origin using the first implanted device alone. The other three bilaterally equipped subjects showed limited localization ability using both devices. Among them one subject demonstrated a side-discrimination ability using only the first implanted device.

Adult↗

PubMed2004

Analysis of ceiling effects occurring with speech recognition tests in adult cochlear-implanted patients.

This article presents a simple method of analysing speech test scores which are biased through ceiling effects. Eighty postlingually deafened adults implanted with a MED-EL COMBI 40/40+ cochlear implant (CI) were administered a numbers test and a sentence test at initial device activation and at 1, 3, 6, 12 and 24 months thereafter. As a measure for speech recognition performance, the number of patients who scored at the 'ceiling level' (i.e. at least 95% correct answers) was counted at each test interval. Results showed a quick increase in this number soon after device activation as well as a continuous improvement over time (numbers test: 1 month: 51%; 6 months: 73%; 24 months: 88%; sentence test: 1 month: 33%; 6 months: 49%; 24 months: 64%). The new method allows for the detection of speech recognition progress in CI patient samples even at late test intervals, where improvement curves based on averaged scores are usually assuming a flat shape.

Adult↗