[Audiovestibular exploration of the brain stem (author's transl)].

In the context of a postgraduate lecture for specialist physicians, the author describes techniques of objective audiology used on a daily basis in the exploration of the brain stem in the ENT department of Lariboisiere Hospital. The following are reviewed for each of them: --the corresponding anatomical pathways, --the principles and techniques used. The results are illustrated by examples. Increase in the threshold of stapes acoustic reflex above 95 dB on a frequency of 1,000 Hz is highly suggestive of acoustic nerve involvement or the lower part of the brain stem (bar sign). By contrast, the threshold is normal in endocochlear and supratentorial disorders. Comparison of abnormalities in stapes acoustic reflex in ipsi and contralateral stimulation, and in particular analysis of changes in their dynamics, often makes it possible to localise the problem to the acoustic nerve, the facial nerve or the brain stem itself. Recording of brain stem evoked auditory potentials (BERA), combined if necessary with that of the electro-cochleogram, is a delicate technique. This is the most useful and most precise audiological tool available to make a precise diagnosis of acoustic neuroma and to localise brain stem disease.