Superior Oblique Myokymia

Uniquesymptomsof brief (one to four second) recurring episodes of torsional diplopia with tremorous sensations in one eye, shimmering oscillopsia, or both, anduniocular signsof a high frequency (12 to 15 per second), pendular, low amplitude (1 to 20) vertical and rotary microtremor began spontaneously and persisted as a stereotyped ocular stabilization defectin five healthy adults(ages 23 to 45). Periodic intorsion of the affected eye and rapid phasic electromyographic activity in a superior oblique, and the absence of reciprocal phasic inhibition in its antagonist, suggested a nuclear (brain stem) disorder. The report describes the phenomenology and natural history of this symptomatically obtrusive, but previously undefined,benign myokymia-like syndrome of the superior oblique muscle.