[Acquired and congenital monocular pendular nystagmus. A comparative electronystagmographic study of two cases...

Comparative analysis of two cases of monocular pendular nystagmus (MPN). The nystagmus was acquired in one case of multiple sclerosis, and congenital in the other patient who had achromatopsia. A postsaccadic inhibition of 0.6-1 sec duration was seen only in the case of acquired MPN. All the other characteristics of the acquired and congenital monocular nystagmus were identical. The waveform of the nystagmus was sinusoidal, triangular or mixed. There was no modification of the MPN by eye position or by smooth pursuit. The nustagmus was inhibited by lid closure. Oscillopsia was reported by both patients. A peculiar disturbance of the sensorimotor feedback loop of the visual system is discussed as the possible common pathogenesis of acquired and congenital pendular nystagmus.