Determining fitting ranges of various bone conduction hearing aids.

OBJECTIVES: To define fitting ranges for nine bone conduction devices (BCDs) over different frequencies based on the device's maximum power output (MPO) and to validate the assessment of MPO of BCDs in the ear canal. BACKGROUND: Maximum power output (MPO) is an important characteristic when fitting BCDs. It is the highest output level a device can deliver and is one of the major determinants of a device's fitting range. A skull simulator can be used to verify MPO of percutaneous BCDs. No such simulator is available for active and passive transcutaneous devices. DESIGN: The MPO of nine different BCDs was assessed either by real-ear measurements and/or with skull simulator measurements. MAIN OUTCOME MEASURES: MPO and cross-validation of the methods using the Bland-Altman method. RESULTS: Percutaneous BCDs have higher MPO levels compared to active and passive transcutaneous devices. This results in a wide dynamic range of hearing for percutaneous devices. Moreover, the assessment of MPO by real-ear measurements was validated. CONCLUSION: Based on MPO data, fitting ranges were defined for nine BCDs over seven frequencies.

Eighth cranial nerve dysfunction in hyperostosis cranialis interna.

Hyperostosis cranialis interna is a recently described autosomal dominant bone disorder characterised by hyperostosis and osteosclerosis confined to the skull, especially the calvarium and the skull base. In the affected family members, we found variable simultaneous involvement of cranial nerves I, II, VII and VIII from late childhood onwards, most likely due to nerve entrapment. Auditory and vestibular functions were followed in 3 young family members for 8 years. At the first examination, pure tone audiograms were normal in all 3 cases and case 1 showed no caloric response in the right ear. During follow-up, this ear developed severe hearing loss progressing to deafness. The left ear showed transient sensorineural hearing loss and a temporarily diminished caloric response. Similar observations were made in case 2. Both cases showed abnormal brain stem auditory-evoked responses during and after the sudden hearing loss, in which initially only wave I was preserved and later on wave V returned with significantly prolonged I-V interval. The latter phenomenon was also observed in case 3 on both sides in the presence of normal audiograms during and after transient unilateral facial nerve paralysis, which was accompanied by bilateral diminished caloric responses.

Auditory abnormalities, including 'precocious presbyacusis', in myotonic dystrophy.

Auditory function tests were performed on 13 patients with myotonic dystrophy (MD). Seven patients had a sensorineural high-frequency hearing loss (HFL) of 30-85 dB at 8 kHz in their pure-tone audiogram, which was in excess of that expected for their age and could be attributed to MD. Their hearing loss resembled 'precocious presbyacusis', i.e. if the patients had been considerably older (or 'functionally' older) than they really were, their HFL could (to some extent) have been attributed to presbyacusis alone. The HFL showed the phenomenon of (genetic) anticipation. Tympanograms and acoustic reflexes were normal. Brainstem auditory evoked potentials (BAEPs) showed a significant increase in the I-V interpeak interval (by 0.35-0.7 ms) and in the III-V interpeak interval (by 0.21-0.67 ms). There was no correlation between the BAEP and the audiometric findings. It should be noted that precocious presbyacusis may be linked to specific gene defects.

Differential premature termination of transcription as a proposed mechanism for the regulation of coronavirus gene expression.

We propose that the different subgenomic mRNA levels of coronaviruses are controlled through differential premature termination of transcription, and are modulated by the relative strength of transcriptional initiation/blockage events. We present the complete set of sequences covering the leader encoding and intergenic regions of the MHV-A59 strain. A computer-assisted analysis of the two now complete sets of these sequences of strain IBV-M42 and MHV-A59 shows that, in contrast to the previous theory, differences amongst stabilities of intermolecular base-pairings between the leader and the intergenic regions are not sufficient to determine the mRNA gradients in both MHV and IBV infected cells. Neither can the accessibility of the interacting regions on the leader and the negative stranded genome, as revealed by secondary structure analysis, explain the mRNA levels. The nested gene organisation itself, on the other hand, could be responsible for observed mRNA levels gradually increasing with gene order. Relatively slow new initiation events at intergenic regions are proposed to block elongation of passing transcripts which, via temporary pausing, can cause premature termination of transcription. This effects longer transcripts more than shorter ones.