Nystagmographic Analysis of the Fistula Symptom.

An electronystagmographic examination of the fistula symptom was carried out to ascertain the relation to pressure, the temporal pattern and the reversability of the nystagmus. The relation of nystagmus-intensity to pressure is not constant, often this relation is expressed by an s-curve. The nystagmus does not increase significantly above intensities of 70 degrees/s. The nystagmus-intensity has a typical temporal pattern: it starts immediately after application of pressure and for several seconds to minutes it practically remains on this level. Subsequently it slowly decreases. When, with a constant pressure, the nystagmus had faded out entirely, then, under relief of pressure, a nystagmus with reverse direction but equal intensity appears. After obtaining a fistula symptom there is a relative refractory time, which sometimes lasts for minutes. Only the change of pressure (which may have an effect of up to several minutes) and not the pressure by itself is decisive for the release of fistula symptom.