Klinische und audiologische Befunde von Kindern mit auditorischer Neuropathie und ihre Versorgung mit einem Cochlea-Implantat

BACKGROUND

Auditory neuropathy is a disorder characterised by preservation of outer hair cells function with normal otoacoustic emissions (OAEs), but with absent auditory brainstem responses (ABR). Perisynaptic synchronisation disorder is one of the possible pathogenesis underlying auditory neuropathy. In this paper we describe the clinical presentation and audiological findings in pediatric auditory neuropathy and its management.

PATIENTS AND METHODS

9 children with auditory neuropathy could be included in the study. An audiological evaluation was performed in all children including behavioural audiometry, measurement of the OAEs as well as electrocochleography (ECoG) and ABR recordings. Children who failed to get any benefit from conventional amplification received a cochlear implant. Prior to implantation the responses to electrical stimuli were examined with the promontory test and with the electrically evoked ABR.

RESULTS

One child showed auditory neuropathy only on one side with normal hearing thresholds on the contralateral ear. Another child had normal hearing thresholds after the follow up period. Four children received a hearing aid. But variable hearing reactions were observed. Thus in three cases a CI is planned. In three children cochlea implantation was done. Following implantation a remarkable improvement in hearing/speech capabilities with the CI compared to conventional hearing aids were observed in all three cases. Beside, these three children developed open set speech discrimination and are using now oral language for communication.

CONCLUSIONS

Auditory neuropathy is a disorder which presents with different clinical and audiological findings. Thus the management of this disorder must be an individual one. In light of our findings we support the use of cochlear implants as an option for children with auditory neuropathy in cases where conventional amplification does not work sufficiently.

Analyzing the cellular contribution of bone marrow to fracture healing using bone marrow transplantation in mice

The bone marrow is believed to play important roles during fracture healing such as providing progenitor cells for inflammation, matrix remodeling, and cartilage and bone formation. Given the complex nature of bone repair, it remains difficult to distinguish the contributions of various cell types. Here we describe a mouse model based on bone marrow transplantation and genetic labeling to track cells originating from bone marrow during fracture healing. Following lethal irradiation and engraftment of bone marrow expressing the LacZ transgene constitutively, wild type mice underwent tibial fracture. Donor bone marrow-derived cells, which originated from the hematopoietic compartment, did not participate in the chondrogenic and osteogenic lineages during fracture healing. Instead, the donor bone marrow contributed to inflammatory and bone resorbing cells. This model can be exploited in the future to investigate the role of inflammation and matrix remodeling during bone repair, independent from osteogenesis and chondrogenesis.

[Development of a new test for speech audiometry in children and results in CI children]

BACKGROUND

Speech audiometry plays an important role for hearing evaluation in children. Hearing impaired children, such as those with cochlear implant (CI) who frequently undergo testing, learn the test words by heart. Furthermore, the standard tests use words of former time.

PATIENTS AND METHODS

Using the most frequently words of modern children's literature a speech assessment test was developed for children between 1 to 8 years. The material was first evaluated on normal hearing children. In a second step the phoneme and word perception scores of 35 CI children were measured using 60 - 100 dB SPL according to the most comfortable level (MCL) in free sound field.

RESULTS

The performance-intensity function for the single words were highly comparable with those of the Freiburger or Göttinger speech perception test. The average speech reception threshold in CI children was 44 % (test I), 36 % (test II), 63 % (test III) and 69 % (test IV), respectively. Compared to the Mainzer and Göttinger speech perception test the new words were more difficult to understand than those of the known tests. However, a statistically significant difference could be noted only for test II.

CONCLUSIONS

The new developed "Würzburger speech perception test" appears to be a useful additional tool for the evaluation of hearing impaired children in addition to the standard test procedures.

Sound localization and sensitivity to interaural cues in bilateral users of the Med-El Combi 40/40+cochlear implant system

OBJECTIVE

The purpose of this study was to investigate sound localization in subjects bilaterally implanted with MED-EL COMBI 40/40+ cochlear implants. In addition, the sensitivity to interaural cues was assessed.

METHODS

In the localization test (11 subjects), CCITT noise (500 ms, original and HRTF-filtered, 70/75/80 dB sound pressure level) was presented from one of seven loudspeakers between -90 degrees and 90 degrees azimuth. The subject had to indicate which loudspeaker the noise was presented from. Sensitivity to interaural level differences (ILD) was assessed by performing localization tests (4 subjects) with the loudness of the two speech processors unbalanced to various degrees. To investigate the subjects' sensitivity to interaural time differences (ITD), lateralization was measured (7 subjects) as a function of the time difference between two Gaussian-like pulses, each directed to one of the subject's speech processor microphones by way of headphones.

RESULTS

The judgments of all subjects significantly correlated with the positions of the loudspeakers. The scatter in the judged azimuth measured by the standard deviation of the responses was on average 27.5 degrees . Unbalanced loudness of the speech processors produced a bias in azimuth toward the speech processor with the louder volume setting. The mean rate of shift was 1.4 degrees per unit on the Wuerzburg loudness scale. Six of seven subjects showed a significant sensitivity to ITDs with the approximate time difference required for complete lateralization being 1,200 micros on an average. The one subject not showing a sensitivity to ITDs performed worst in the localization test.

CONCLUSIONS

Bilateral cochlear implantation can restore spatial hearing in cochlear implant users. Both ILDs and ITDs are used by bilateral cochlear implant users in sound localization with ILDs appearing to be the dominant cue.

Bilateral cochlear implants: a way to optimize auditory perception abilities in deaf children?

OBJECTIVES

The Würzburg bilateral cochlear implant (CI) program was started with the aim to improve the patients' communicative abilities in complex listening situations. In this study, the auditory skills of children using bilateral cochlear implants were evaluated.

STUDY DESIGN AND SETTINGS

Qualitative data based on free observations in the rehabilitation setup were collected in 39 bilaterally implanted children. A speech discrimination in noise test was performed in 18 of these children; lists of bisyllabic words were presented in noise at a signal to noise ratio (SNR) of +15 dB.

RESULTS

Qualitative and quantitative data show clearly that bilateral CI improves the children's communicative behaviour, especially in complex listening situations. Children examined with the speech in noise test scored significantly better under the bilateral condition compared to the unilateral condition. Integration of the second implanted side and use of binaural information was observed to be easier and faster in children with a short time lag between both implants.

CONCLUSIONS

To be able to obtain optimal benefit from bilateral cochlear implants, an intensive rehabilitation program is necessary. The important aspects of such a program are creating realistic expectations in older children before implantation; performing the first processor fitting of the second side with the first side switched on; and separate intensive training with the new system in order to balance out the hearing competence of the second CI with that of the first.

Cochlea-Implantation: Ergebnisse und Kosten, eine Übersicht

The cochlear implantation, especially after bilateral operation provides a reliable and outstanding compensation in bilateral complete deafness or severe hearing impairment. Directional hearing can be restored with bilateral implantation so that warning signals are localized correctly and speech in noise is easier understood. Thus, rehabilitation is restored to a high degree. The involved expenses are severe, but are lower for the society when compared to the amount of money necessary to substitute a completely deaf patient lifelong.