The co-occurrence of jerk and pendular nystagmus

This patient presented with significant oscillopsia from both spontaneous horizontal pendular nystagmus in addition to upbeat nystagmus. At first glance, the combination of jerk and pendular nystagmus gives a complex appearance, but ophthalmoscopy can be a powerful tool to help dissect the waveforms and better characterize the movements. Eye tracking and video-oculography can also be helpful in such cases when available. Jerk and pendular nystagmus can occasionally co-exist, often due to infantile nystagmus (spontaneous jerk or pendular and gaze-evoked nystagmus), multiple sclerosis (spontaneous pendular and gaze-evoked or abducting nystagmus in internuclear ophthalmoplegia), oculopalatal tremor (OPT, spontaneous pendular and gaze-evoked nystagmus from a posterior fossa insult). Despite the fact that the combination of this patient's high frequency horizontal pendular nystagmus paired with upbeat nystagmus was suggestive of a posterior fossa lesion (especially involving the midline brainstem), multiple MRIs were unrevealing without evidence of demyelination. There was no palatal tremor and the onset was 2-3 years prior, making OPT and infantile nystagmus unlikely, respectively. There was no clear evidence of optic nerve or retinal disease, and while additional investigations were ordered, the patient was lost to follow-up.