Superior Oblique Myokymia Presumed Due to Large Posterior Fossa Arteriovenous Malformation

A 26-year-old female presented with a complaint of intermittent oscillopsia and binocular vertical diplopia for the past 5 years. Over the past several months, she had noticed intermittent pulsatile tinnitus. She was otherwise healthy with no previous history of trauma and had no other visual or neurologic complaints. In Neuro-ophthalmology clinic, she was found to have 20/15 vision in both eyes with full ocular motility. There was a small exophoria in primary position and small esophoria in downgaze. Her slit lamp and fundus examinations were normal. During the assessment, the left eye was noted to undergo high-frequency, small amplitude incyclotorsional oscillations for a few seconds at a time (Video 1 in the supplementary material), which she was able to provoke by looking down. The diagnosis of superior oblique myokymia was made, and an MRI/MRA of the brain was requested.