Formant frequency discrimination with a fine structure sound coding strategy for cochlear implants.

Recent sound coding strategies for cochlear implants (CI) have focused on the transmission of temporal fine structure to the CI recipient. To date, knowledge about the effects of fine structure coding in electrical hearing is poorly charactarized. The aim of this study was to examine whether the presence of temporal fine structure coding affects how the CI recipient perceives sound. This was done by comparing two sound coding strategies with different temporal fine structure coverage in a longitudinal cross-over setting. The more recent FS4 coding strategy provides fine structure coding on typically four apical stimulation channels compared to FSP with usually one or two fine structure channels. 34 adult CI patients with a minimum CI experience of one year were included. All subjects were fitted according to clinical routine and used both coding strategies for three months in a randomized sequence. Formant frequency discrimination thresholds (FFDT) were measured to assess the ability to resolve timbre information. Further outcome measures included a monosyllables test in quiet and the speech reception threshold of an adaptive matrix sentence test in noise (Oldenburger sentence test). In addition, the subjective sound quality was assessed using visual analogue scales and a sound quality questionnaire after each three months period. The extended fine structure range of FS4 yields FFDT similar to FSP for formants occurring in the frequency range only covered by FS4. There is a significant interaction (p = 0.048) between the extent of fine structure coverage in FSP and the improvement in FFDT in favour of FS4 for these stimuli. FS4 Speech perception in noise and quiet was similar with both coding strategies. Sound quality was rated heterogeneously showing that both strategies represent valuable options for CI fitting to allow for best possible individual optimization.

Audiological performance in cochlear implanted patients deafened by meningitis depending on duration of deafness.

The objective of our study was to evaluate audiological outcome in cochlear implanted children deafened by meningitis and its correlation with duration of deafness from meningitis in a retrospective clinical study at an academic tertiary referral center. Sixty patients profoundly deafened by meningitis were evaluated. Two groups of children depending on duration of deafness--group 1 defined by duration of deafness less than 6 months and group 2 defined by duration of deafness over 6 months were evaluated. The control group A (duration of deafness <6 months) and group B (duration of deafness >6 months) with similar demographics data and a non-meningitis-related cause of deafness were evaluated. Patient history, cochlear implantation and audiological findings (MAIS, MUSS and open set tests questionnaire) were investigated. Standardized diagnostic and therapeutic procedure was performed in all patients. Our results showed better auditory performance and language control in children implanted within 6 months after meningitis. Over the period of 36 months group 2 was able to catch up with the group 1 in the MUSS and MAIS tests. However, the results of the common phrases test remain significantly better in group 1 over this time period (P=0.0188). In case of meningitis, audiological and radiological assessment should be performed within 4 weeks after the onset of disease. We see a clear indication for immediate implantation in patients with profound SNHL caused by meningitis. The aim should be bilateral implantation in this population to achieve the best possible performance by implantation before obliteration occurs. Premeningetic auditory experience is an important advantage which should be used. Frequent bilateral and sometimes late obliteration should be taken into consideration in the decision-making process as well.

[Exostosis of the internal auditory canal in a patient with myotonic dystrophy]. / Exostosenbildung des inneren Gehörganges bei einem Patienten mit myotoner Dystrophie Curschmann-Steinert.

A 53-year-old patient with myotonic dystrophy presented to our clinic with progressive bilateral hearing loss. The ENT status and particularly the otological examination were without pathological signs. Pure tone audiograms showed a bilateral moderate to severe sensorineural hearing loss. Routinely performed computed tomography of the temporal bones revealed the rare picture of exostosis of the internal auditory canals and the medial surface of the petrous bones. To our knowledge, this is the first report describing exostosis of the internal auditory canal in a patient with myotonic dystrophy, although at present it remains unclear in how far there is a causal connection between these two pathologies.