[Intensity of the vestibulo-ocular reflex as a response to thermal labyrinth stimulation with water and air. Comparative studies of the stimulus intensity in thermal vestibular assessment in healthy probands].

In 22 otoneurologically healthy subjects (44 ears) the response of the labyrinthine system to stimulation was studied for the method using water, standardized according to Mulch and Scherer (1980), and for our method of stimulation by air. The mean values of the speed of the slow phase and of the total amplitude of the vestibular nystagmus were significantly lower in case of air stimulation. If we consider each stimulus modality separately, the nystagmus parameters correlate significantly in the right-left comparison, and likewise the right predominant nystagmus with the left predominant nystagmus. However, on comparing the data measured for air stimulation and for water stimulation, no correlation could be established. The reason is thought to be an energetic one, since the method using air depends on heat capacity and heat transfer, whereas the method employing water depends on heat transfer only. Calculation shows that the energetic conditions of the method employing air are of the same order of magnitude as the roughly quantitative minimal rinse when filling the auditory meatus with water of moderate temperature. Hence, thermal stimulation of the labyrinthine system with air reacts very sensitively to changes in experimental conditions, so that all conditions must be strictly adhered to and standardised and the examination methods must be repeatable within narrow tolerance limits. On account of its low mean values and great susceptibility to variation, the method of air stimulation should be discouraged, especially in the assessment of patients who are suspected of suffering from a disease of the vestibulum auris.