gms | German Medical Science

Voluntary nystagmus is important as a differential diagnosis of many forms of acquired spontaneous nystagmus in patients from 4 years of age. The mode of inheritance is autosomal dominant with incomplete penetrance, but in some sources heredity is doubted.

We examined 2 families from the Lübeck area orthoptically, with video and with search-coil technique or electronystagmography. 3 members of 3 generations of the first family could generate a horizontal voluntary nystagmus. A 9-years-old boy from a second family not related to the first one, showed beside congenital esotropia and hyperopia mainly an intermittent horizontal nystagmus with oscillopsia that he could induce voluntarily or that came unwanted during longer reading.

The examination of the first family showed similar characteristics in grandfather's, mother's and 8-years-old boy's nystagmus. The nystagmus could be generated on demand over a period of 2 to 5 sec. and had small amplitudes (1° to 4°) and high frequencies of 15 Hz. In the second family no further member could produce this nystagmus. Our patient generated voluntarily a nystagmus of about 5° and 10 Hz for max. 20 sec. During longer reading attempts the same nystagmus with disturbing oscillopsia evolved and was not suppressible. We added +0,75 D to both spectacle glasses reaching the cycloplegic refraction and so stopped the unwanted nystagmus on near fixation without changing the voluntary induced nystagmus.

A phenomenon appearing in 3 consecutive generations as well as isolated (new mutation) is typical for an autosomal dominant mode of inheritance. The published ranges of frequencies for voluntary nystagmus are between 10 and 20 Hz and the amplitudes between 3° and 8°. The measured data from our first family can be found in one range of this spectrum, that of the boy from the second family in a quite different range still being in the limits described above. Therefore, family specific forms of voluntary nystagmus could be considered.