Abstract
Purpose: :
It is well known that a physiologic nystagmus such as horizontal OKN or vestibular nystagmus can vectorially add with a different physiologic or pathologic nystagmus. Four patients are presented demonstrating two other ways that two different types of nystagmus can exist in the same patient.
Methods: :
Four patients seen in neuro-ophthalmologic consultation are described.
Results: :
The first two patients had a primary position horizontal nystagmus. After horizontal headshaking there was a brisk nystagmus in the opposite direction. After vertical headshaking there was an increased nystagmus in the original direction. It is assumed that the primary position nystagmus was central and that a latent peripheral nystagmus was brought out with headshaking. Two additional patients with MS had a primary position pendular nystagmus that converted to a jerk nystagmus on lateral gaze to either side. Recordings of both patients showed that there was a smaller amplitude, higher frequency nystagmus with a different wave form superimposed on the gaze-evoked nystagmus.
Conclusions: :
There are at least three mechanisms by which nystagmus of different types can exist in the same patient.1) Vector summation of two types of nystagmus sharing a single beat frequency.2) A manifest central vestibular nystagmus with cancellation of a peripheral vestibular nystagmus that can be brought out with head shaking.3) A superimposition of two different types of nystagmus with different wave forms and different frequencies.
Keywords: nystagmus • neuro-ophthalmology: diagnosis • eye movements