Multicentre investigation on electrically evoked compound action potential and stapedius reflex: how do these objective measures relate to implant programming parameters?

Objectives: The aims of this study were to collect data on electrically evoked compound action potential (eCAP) and electrically evoked stapedius reflex thresholds (eSRT) in HiResolutionTM cochlear implant (CI) users, and to explore the relationships between these objective measures and behavioural measures of comfort levels (M-levels). Methods: A prospective study on newly implanted subjects was designed. The eCAP was measured intra-operatively and at first fitting through neural response imaging (NRI), using the SoundWaveTM fitting software. The eSRT was measured intra-operatively by visual monitoring of the stapes, using both single-electrode stimulation and speech bursts (four electrodes stimulated at the same time). Measures of M-levels were performed according to standard clinical practice and collected at first fitting, 3 and 6 months of CI use. Results: One hundred seventeen subjects from 14 centres, all implanted unilaterally with a HiResolution CII Bionic Ear® or HiRes 90K®, were included in the study. Speech burst stimulation elicited a significantly higher eSRT success rate than single-electrode stimulation, 84 vs. 64% respectively. The NRI success rate was 81% intra-operatively, significantly increasing to 96% after 6 months. Fitting guidelines were defined on the basis of a single NRI measurement. Correlations, analysis of variance, and multiple regression analysis were applied to generate a predictive model for the M-levels. Discussion: Useful insights were produced into the behaviour of objective measures according to time, electrode location, and fitting parameters. They may usefully assist in programming the CI when no reliable feedback is obtained through standard behavioural procedures

Novel and recurrent non-truncating mutations of the MITF basic domain: genotypic and phenotypic variations in Waardenburg and Tietz syndromes.: Non-truncating mutations of the MITF basic domain

International audienceThe microphthalmia-associated transcription factor (MITF) is a basic helix-loop-helix leucine zipper transcription factor, which regulates melanocyte development and the biosynthetic melanin pathway. A notable relationship has been described between non-truncating mutations of its basic domain and Tietz syndrome, which is characterized by albinoid-like hypopigmentation of the skin and hair, rather than the patchy depigmentation seen in Waardenburg syndrome, and severe hearing loss. Twelve patients with new or recurrent non-truncating mutations of the MITF basic domain from six families were enrolled in this study. We observed a wide range of phenotypes and some unexpected features. All the patients had blue irides and pigmentation abnormalities that ranged from diffuse hypopigmentation to Waardenburg-like patches. In addition, they showed congenital complete hearing loss, diffuse hypopigmentation of the skin, freckling and ocular abnormalities, more frequently than patients with MITF mutations outside the basic domain. In conclusion, the non-truncating mutations of the basic domain do not always lead to Tietz syndrome but rather to a large range of phenotypes. Sun-exposed freckles are interestingly observed more frequently in Asian populations. This variability argues for the possible interaction with modifier loci