Daniel R. Gold, DO, Departments of Neurology, Ophthalmology, Neurosurgery, Otolaryngology - Head & Neck Surgery, Emergency Medicine, and Medicine, The Johns Hopkins School of Medicine
Both of these patients have MS and monocular (OS) horizontal pendular nystagmus. The first patient seen in the video has normal afferent function and no evidence of optic nerve disease in either eye, while the second patient has severe OS>>OD optic nerve disease related to bouts of optic neuritis (there was also a slight torsional pendular nystagmus component). Because pendular nystagmus is commonly seen in MS patients, it has been suggested that the nystagmus might result from a prolonged response time for visual processing, supported by the fact that nystagmus is commonly more intense in the eye with poorer vision. However, pendular nystagmus doesn't change with visual feedback removed, and inducing visual delays by itself is not capable of causing the oscillations seen in MS. Therefore, it's likely that instability in the neural integrator (gaze holding machinery) also plays a significant role in many cases. Explanations for monocular pendular nystagmus in these patients includes 1) ipsilateral afferent dysfunction or 2) perhaps within the unstable neural integrator, certain monocular-projecting cell populations are preferentially damaged.
Spencer S. Eccles Health Sciences Library, University of Utah