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Biomedical subjects

T Lenarz

Publications and source records attributed to T Lenarz.

At least 109 records · Page 6Linked to original sources
PubMed1997

[Intraoperative evaluation of signal transduction of prototypes of implantable hearing aid transducers in the human].

During routine middle ear surgery prototypes of implantable piezoelectric hearing aid transducers were coupled to the ossicular chain of 28 patients. Pure tone thresholds in a broad frequency range (250 Hz-8 kHz) and perception of music were the basis of psychoacoustic evaluation of the transfer properties of the prototypes in this human study. The piezoelectric transducer reached an equivalent transducer sound-pressure level of up to 145 dB SPL and frequencies of 10 kHz. The dynamics for music reached 32 dB, which was identical with the results of the preoperative investigations using hi-fi headsets (33 dB). The low nonlinear distortions of around 0.1% and the frequency range up to 10 kHz are reflected in the positive evaluation of sound quality by 84% of the patients involved. The study is the basis for realizing a piezoelectric transducer designed for routine clinical implantations. The transducer is thought to be part of a totally implantable future hearing aid for rehabilitation of moderate and severe sensory neural hearing loss predominantly in the middle and high frequency range.

Adult↗
PubMed1997

[Primary intra-meatal invasion of meningioma into the left meatus acusticus internal in a 49-year-old woman].

BACKGROUND: Meningiomas originating in the internal auditory meatus are rare and have been reported in only 12 cases. PATIENT: We report about another case, which showed primarily the symptoms of sudden hearing loss and diagnostic signs of an intrameatal acoustic neuroma. The ABR interpeak latency IV was prolonged. The tumor was detected by MRI scan with gadolinium contrast enhancement and resembled the features of an intrameatal acoustic neuroma. RESULTS: The tumor was removed via a middle fossa approach with preservation of hearing and facial nerve function. Histological examination however revealed a meningioma originating from the internal auditory meatus. CONCLUSIONS: Contrast enhancing intrameatal tumors are most often acoustic neuromas. However even despite subtile audiological and neurotological examination and sophisticated imaging techniques they cannot be differentiated clinically from meningiomas at this location. Removal of the intrameatal tumor via a middle fossa approach seems to be the best surgical approach to preserve hearing and facial nerve function.

Audiometry, Pure-Tone↗
PubMed1997

[Cochlear implant in patients with residual hearing].

INTRODUCTIONS: Cochlear implants are used for the rehabilitation of bilaterally deaf patients. Due to the improvements in speech processing they might be also useful for patients with residual hearing and some speech understanding. METHODS: Pre- and postoperative speech understanding scores in 26 patients receiving implants were evaluated in a retrospective study. RESULTS: The preoperative pure-tone threshold in the implanted ear was between 80 and 115 dB in the frequency range of 500 to 2000 Hz. On the contralateral side the mean threshold was 10 dB better. The mean score for the number test was 11.3%, for the monosyllables below 5%. Postoperatively speech understanding improved significantly up to 97% for numbers and 48% for monosyllables (tested with the Freiburger Speech Test). Cochlear implantation also benefits patients with residual hearing and some speech understanding with hearing aids under optimum conditions. The speech understanding scores must be below certain limits. General selection criteria cannot yet be specified. The individual decision must be based upon several criteria, especially the speech understanding scores in quiet and noise under optimum conditions. A prospective study is needed to develop generally applicable criteria.

Audiometry, Pure-Tone↗
PubMed1997

Optical imaging of cat auditory cortex cochleotopic selectivity evoked by acute electrical stimulation of a multi-channel cochlear implant.

We measured reflectance changes by means of optical imaging of intrinsic signals to study the effects of acute electrical cochlear stimulation on the topography of the cat auditory cortex. After single-pulse electrical stimulation at selected sites of a multichannel implant device, we found topographically restricted response areas representing mainly the high-frequency range in AI. Systematic variation of the stimulation pairs and thus of the cochlear frequency sites revealed a systematic and corresponding shift of the response areas that matched the underlying frequency organization. Intensity functions were usually very steep. Increasingly higher stimulation currents evoked increasingly larger response areas, resulting in decreasing spatial, i.e. cochleotopic, selectivity; however, we observed only slight positional shifts of the focal zones of activity. Electrophysiological recordings of local field potential maps in the same individual animals revealed close correspondence of the locations of the cortical response areas. The results suggest that the method of optical imaging can be used to map response areas evoked by electrical cochlear stimulation, thereby maintaining a profound cochleotopic selectivity. Further experiments in chronically stimulated animals will shed more light on the degree of functional and reorganizational capacities of the primary cortex and could be beneficial for our understanding of the treatment of profound deafness.

Animals↗
PubMed1997

Performance in quiet and in noise with the Nucleus Spectra 22 and the Clarion CIS/CA cochlear implant devices.

The demographic characteristics and functional results from two cochlear implant adult patient groups are reported. The first group of subjects, implanted with the Nucleus Mini 22 Cochlear Implant System utilized the SPEAK coding strategy available in the SPECTRA 22 speech processor. The second group of subjects, implanted with the Clarion Cochlear Implant System used the CIS coding strategy with the exception of one patient utilizing the CA speech coding strategy. Data are available for 130 Nucleus subjects who were evaluated following 1 month of use of the SPEAK coding strategy. Data for the second group of subjects became available following administration of the Nucleus test battery to 38 Clarion subjects with varying implant experience. The test results presented include one common open set speech perception measure for all patients, the Freiburger monosyllabic word (FMW) tests. Additional subsequent test measures were taken from an adaptive test protocol assessing performance in quiet and quiet and two noise conditions. The results of this study conclude that both subject groups displayed similar distribution of performance scores on Freiburger Monosyllabic Words despite the large difference in group numbers. Both device groups also demonstrated a similar degree of deterioration in performance with increased background noise. This paper describes the results observed for each group.

Adolescent↗
PubMed1997

[Patients with trauma-induced deafness--rehabilitation using a cochlear implant].

Deafness due to bilateral temporal bone fractures is a dramatic consequence for the injured patients. Out of more than 1000 patients in Hannover which received a cochlear implant we analyzed the medical history of 44 patients (36 male, 8 female, average age of adults: 41 years) which were implanted after posttraumatic deafness (Nucleus device n = 33, Clarion device n = 11). Postoperatively the patients underwent an auditory rehabilitation program. Most of them (84%) reached open set speech understanding. Results are different caused by additional damage of auditory nerve fibers and posttraumatic central lesions. Due to the risk of posttraumatic fibrosis of the cochlea, implantation should be performed early and can be recommended to the patient if bilateral deafness is diagnosed. In the case of auditory nerve damage brain stem implants offer new possibilities.

Adolescent↗