Symptoms in Ménière’s disease are explained by hydrops of the endolymphatic system with recurrent ruptures of the membranous labyrinth. The primary cause of the increased endolymphatic volume appears to be an imbalance between secretion and resorption of endolymph which may be due to an obstruction of the endolymphatic duct and sac, located in the vestibular aqueduct (VA). Non-visualization or narrowing of the latter have been demonstrated by conventional tomography. Also, sclerosis and hypoplasia of the retrolabyrinthine portions of the temporal bone have been documented. By high resolution computed tomography (CT) we prospectively tried to demonstrate morphological alterations in 10 patients with Ménière’s disease. These were compared with a group of 14 non-Ménière patients. Visualization of the VA as well as perilabyrinthine pneumatization were assessed and the width of the retrolabyrinthine part of the temporal bone was measured. Whereas there was a slight difference in the average retrolabyrinthine width (3.8 mm in Ménière versus 5.8 in non-Ménière cases) and degree of pneumatization, there was a distinctly decreased visualization of the VA in the Ménière group. As findings were always bilateral and only 3 of 20 temporal bones showed peripheral hypopneumatization, possibly due to chronic otitis mediathe theory of a predisposing constitutional abnormality must be taken into consideration. However, we were not able to confirm a statistically proven usefulness of the CT technique in identifying an anatomical abnormality which is directly in correlation with the side of the lesion in cases of unilateral Ménière’s disease.

In Switzerland, the program for the prevention of occupational hearing loss is carried out by the Swiss National Accident Insurance Organization (SUVA). About 50,000 people are examined each year by means of six mobile examination units (‘‘audiomobiles’’). Most of these people are exposed to potentially hazardous noise at their working places. In recent years, several groups of nonindustrial noise-exposed people (NINEP) have been included also with the aim to create a control group data base. In order to get representative NINEP data, different criterion have to be considered and will be discussed. Social, national, and economic differences are probably as important as differences in noise exposure at work. The hearing of workers in different occupations is compared—distinct by age and sex—to the NINEP group. NINEP subgroups screened in different ways are compared and the results are discussed. All the hearing loss data are compared to the reference values in Appendix B of ISO 1999-1990. Some general considerations concerning the problem of arriving at comparable NINEP data for the evaluation of the effectiveness of hearing conservation programs will also be presented.