[The status of galvanic assessment of equilibrium]

The galvanic test is the only method of localising the site of the disease in the differential diagnosis between a vestibular endorgan or neuronal lesion. The galvanic nystagmus persists even after complete destruction of the inner ear but is impaired as soon as the peripheral vestibular neurone is damaged. We investigated 30 normal subjects, 10 patients with Menière's disease and 20 patients with an acoustic neuroma. The patients had a reduced caloric response on one side. All subjects were stimulated monaural-unipolar. The photoelectronystagmograms were analysed by determining slow phase velocity. For interpretation we used the "relationship of excitability" as described recently by Mulch and Scherer for the thermal test. This procedure seems to be more accurate than the calculation of side difference of excitability as a proportion of total reaction. Furthermore we suggest basing the evaluation of galvanic test by calculating expectation regions for the logarithmic values obtained by right-left stimulation. This method assumes a two dimensional symmetric normal distribution. The parameters lay within the normal range in all patients with Menière's disease whereas they were abnormal in every subject with an acoustic neuroma.