Peripheral-vastibular spontaneous nystagmus. Analysis of reproducibility and methoidolgies.

UNLABELLED: With peripheral spontaneous nystagmus the intensity and its reproducibility was electronystagmorgraphically analyzed with eyes open under Frenzel's glasses and with eyes closed.
RESULTS: 1. The maximum intensity of a spontaneous nystagmus with eyes closed is several times higher than under Frenzel's glasses. 2. A weak nystagmus can, under Frenzel's glasses, only be recognized under favorable conditions. A rather long and careful search in a totally dark room is necessary. 3. With purely peripheral lesions, the spontaneous nystagmus with closed eyes shows large intensity fluctuations, and it may disappear temporarily despite mental arithmetics. Contrary to this, with eyes open under Frenzel's glasses, the intensity fluctuation of the nystagmus is remarkably lower. Therefore, even experimental examinations with patients should be carried out electronystagmorgraphically under Frenzel's glasses. The absolute reaction is lower, but the content of information is higher because of the significantly better reproducibility.