Test Your Knowledge - Monocular Oscillopsia

𝗢𝗿𝗶𝗴𝗶𝗻𝗮𝗹 𝗗𝗲𝘀𝗰𝗿𝗶𝗽𝘁𝗶𝗼𝗻: Which of the following associated signs is most likely to be seen in this patient presenting with oscillopsia? A. Optic nerve pallor B. Palatal tremor C. Severe unilateral cataract D. Head bobbing E. Neurovascular contact on MR CISS/FIESTA imaging A. Correct. This patient has MS and had experienced bilateral attacks of optic neuritis years ago. Vision is poorer in the left compared to the right eye, which is typical when asymmetric or purely unilateral pendular nystagmus is seen in MS. Her ocular motor exam was otherwise completely normal, arguing more for a visual origin of pendular nystagmus - e.g., prolonged response time for visual processing related to optic nerve disease. However, observational studies on patients with MS with pendular nystagmus who had larger oscillations in the eye with the more severe optic demyelination showed that the nystagmus remained unchanged in dark (1). Therefore in most cases an additional mechanism such as integrator instability probably plays a role, at least to some degree. B. Incorrect. While the nystagmus associated with oculopalatal tremor is commonly dissociated or asymmetric, there is usually a vertical and/or torsional component. Regardless, palatal tremor and synchronized movement of other branchial arch muscles should be sought in any patient with pendular nystagmus, and were absent in this patient. There was also no medullary hypertrophic olivary degeneration on MRI. C. Incorrect. The pendular nystagmus associated with the Heimann-Bielschowsky phenomenon is vertical in waveform, as opposed to this patient whose nystagmus has an elliptical waveform. This nystagmus is associated with subnormal vision, and has been associated with significant amblyopia, cataracts or severe refractive error among other ocular etiologies, in addition to neuro-ophthalmic etiologies including optic nerve disease. D. Incorrect. Spasmus nutans is characterized by intermittent, small amplitude, high frequency ("shimmering") movements that resemble pendular nystagmus. Typically the nystagmus is dissimilar in the two eyes, more marked in the abducting eye, and occasionally is monocular. This condition is characterized by the triad of nystagmus, head nodding and abnormal head posture (head tilt or head turn), but usually affects children in the first year of life and tends to resolve spontaneously over 2-8 years. E. Incorrect. Superior oblique myokymia (SOM) is occasionally related to neurovascular compression, where monocular torsional movements cause the patient to experience oscillopsia, torsional diplopia or tremulous sensations in one eye - e.g., in left SOM, the irritated left 4th nerve would cause frequent incycloduction movements of the left eye (i.e., the primary action of the SO muscle). These recurrent episodes usually last seconds, can be triggered by blinking, looking down or tilting the head toward the side of the irritated 4th nerve and can best detected by following the movement of a conjunctival vessel during ophthalmoscopy or slit lamp examination. Summary: This is a patient who experienced bilateral attacks of optic neuritis (OS>OD) decades prior, was subsequently diagnosed with MS, and more recently experienced monocular oscillopsia due to elliptical pendular nystagmus in the left eye only. Even with ophthalmoscopy OD, there was no trace of nystagmus. 1. Averbuch-Heller L, Zivotofsky AZ, Das VE, DiScenna AO, Leigh RJ. Investigations of the pathogenesis of acquired pendular nystagmus. Brain 1995;118 ( Pt 2):369-378. 𝗡𝗲𝘂𝗿𝗼-𝗼𝗽𝗵𝘁𝗵𝗮𝗹𝗺𝗼𝗹𝗼𝗴𝘆 𝗮𝗻𝗱 𝗡𝗲𝘂𝗿𝗼-𝗼𝘁𝗼𝗹𝗼𝗴𝘆 𝗧𝗲𝘅𝘁𝗯𝗼𝗼𝗸 𝗟𝗲𝗴𝗲𝗻𝗱: This is a patient who experienced bilateral attacks of optic neuritis (OS>OD) decades prior, was subsequently diagnosed with MS, and more recently experienced monocular oscillopsia due to elliptical pendular nystagmus in the left eye only. Even with ophthalmoscopy OD, there was no trace of nystagmus. https://collections.lib.utah.edu/ark:/87278/s6352s3s