Walsh & Hoyt: Superior Oblique Myokymia (Superior Oblique Microtremor)

Superior oblique myokymia (SOM) was first described by Duane in 1906, but clinicians became generally aware of the disorder following the description by Hoyt and Keane in 1970. Typical symptoms include monocular blurring of vision, tremulous sensations in the eye, brief episodes of vertical or torsional diplopia, and vertical or torsional oscillopsia. Attacks last less than 10 seconds and may occur many times per day; they may be elicited on by looking downward, by tilting the head toward the side of the affected eye, and by blinking. The majority of patients with SOM have no underlying disease, although cases have been reported following trochlear nerve palsy, after mild head trauma, in the setting of MS, after brainstem stroke, and in patients with cerebellar tumor.