Monocular Horizontal Pendular Nystagmus in MS

𝗢𝗿𝗶𝗴𝗶𝗻𝗮𝗹 𝗗𝗲𝘀𝗰𝗿𝗶𝗽𝘁𝗶𝗼𝗻: 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. 𝗡𝗲𝘂𝗿𝗼-𝗼𝗽𝗵𝘁𝗵𝗮𝗹𝗺𝗼𝗹𝗼𝗴𝘆 𝗮𝗻𝗱 𝗡𝗲𝘂𝗿𝗼-𝗼𝘁𝗼𝗹𝗼𝗴𝘆 𝗧𝗲𝘅𝘁𝗯𝗼𝗼𝗸 𝗟𝗲𝗴𝗲𝗻𝗱: Seen here are two patients, both with MS and monocular (OS) horizontal pendular nystagmus causing monocular oscillopsia. 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 multiple episodes of optic neuritis (there was also a slight torsional pendular nystagmus component). Although rare, when APN occurs it is typically due to MS (or oculopalatal tremor), 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, APN 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. https://collections.lib.utah.edu/ark:/87278/s6q852cf