Otoacoustic emissions (OAE) are influenced in their amplitude and frequency spectra by the middle ear. The effects of changes in the middle ear transmission mechanisms on transiently evoked OAE (TEOAE) and distortion product emissions (DPOAE) were investigated as a function of static ear canal pressure in 25 normal-hearing test persons aged 18-35 years. The ear canal pressure was varied stepwise between positive and negative values of 200 daPa. TEOAE and DPOAE amplitudes were attenuated significantly with changes of the static ear canal pressure, with greatest changes at low frequencies (< 2 kHz). The alterations of OAE amplitude were slightly dependent on the polarity of the pressure, with positive pressure producing a greater attenuation (0.6 dB). The results demonstrate that changes in middle ear impedance can cause a misinterpretation of OAE. To avoid this problem, tympanometry should always precede OAE measurements. Alternatively, both methods can be combined using one acoustic probe, so that the emissions can be evoked at the peak of middle ear compliance.

The capacity of different audiological methods to detect a high noise susceptibility was examined in 20 normally hearing and 26 especially noise-susceptible subjects. The latter were selected from 422 soldiers in field studies: they had shown a temporary threshold shift (TTS) in pure tone audiometry (PTA) after regular training with firearms. In laboratory experiments, the TTS-positive soldiers were re-examined using greatly reduced sound intensities, which caused no TTS in a control subject group. Before and after acoustic stimulation, different subjective (PTA, high frequency audiometry (HFA), upper limit of hearing (ULH)) and objective (transiently evoked otoacoustic emissions (TEOAE), distortion products (DPOAE)) audiological tests were performed. After exposure to low impact noise in the laboratory, in both PTA and HFA, a TTS was observed in 11.5% (N = 3) of the noise-susceptible group (compared to 0% in the control group). In the TTS-positive group, deterioration of the ULH occurred in 28% (N = 7) (compared to 15% (N = 3) in the control group). An ULH improvement occurred in only one subject (3.8%) (compared to 25% (N = 5) in the control group). Significant alterations of click-evoked OAE-amplitudes were found in 26.9% (N = 7) of the selected groups, whereas stable emissions were observed in all but one subject (5%) of the control group. However, DPOAE alterations were seen in 19.2% (N = 5) of the TTS-positive soldiers but also in 25% (N = 5) of the control group. These results suggest that TEOAE provides a more sensitive and more objective method of detecting a subtle noise-induced disturbance of cochlear function than do PTA or DPOAE.

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Head and neck squamous cell carcinomas (HNSCC) are common cancers with a relatively poor prognosis. Locoregionale recurrences are regularly encountered and associated with a detrimental outcome. Studies of the last few years report that not only tumor staging and grading influence locoregional control but also histologic and biological markers. One such histological marker is coined "worst pattern of invasion". It describes a histologic growth pattern consisting of invading tumor cell islands and strands that are dispatched from the invasion front (POI typ 4 and 5). Additional features of invasion are perineural invasion and extracapsular nodal extension. Besides histological markers there are molecular characteristics that include the expression of gene families involved in extracellular matrix degradation. The data suggest that head and neck cancers differ with respect to their invasive growth capacity and thus their ability to generate locoregionale recurrences. It appears that locoregionale control is a consequence of this growth pattern. This may explain, why in recent clincial studies the prognostic marker "pattern-of-invasion" outweights even such well established prognosticators such as "surgical margins".

Cochlear outer hair cells (OHC) are capable of auditory perception. In addition, they influence actively the micromechanics of the cochlea. This concept is based on the observation of motile responses induced by electrical and chemical stimuli. OHC motility is probably controlled by the efferent olivo-cochlear system. By means of two monoclonal antibodies against intra- and extracellular epitopes of ACh-receptors a transmembraneous receptor molecule was visualized in the OHC membrane. Besides morphological studies functional investigations using acetylcholine and its analogues were carried out. We observed contractile responses of OHCs that were reversible and dependent on the applied transmitter concentration. We suggest that the high frequency selectivity and sensitivity of the cochlea is modulated by the efferent innervation and the observed ACh-induced OHC motility.