Superior oblique myokymia

Abstract

Superior oblique myokymia (SOM) is a rare condition of unclear etiology. We discuss the history, etiology, clinical features, differential diagnoses, management, and prognosis of SOM. We conducted a meta-analysis of all 116 cases published since SOM was first described in 1906. The age at examination was 17–72 years (mean: 42 years.) There was a right-sided preponderance in 61% of cases (P < 0.02) that was statistically significant in females (63%, P < 0.04) but not in males (59%, P = 0.18). The pathophysiology of SOM may be neurovascular compression and/or ephaptic transmission. Although various pharmacological and surgical approaches to SOM treatment have been proposed, the rarity of the condition has made it impossible to conduct clinical trials evaluating the safety and efficacy of these approaches. Recently, topical beta blockers have managed SOM symptoms in a number of cases, including the first case treated with levobunolol. Systemic medications, strabismus surgery, and neurosurgery have been used to control symptoms, with strabismus surgery carrying a moderate risk of postoperative diplopia in downgaze. Although there is no established treatment for SOM, we encourage clinicians to attempt topical levobunolol therapy before considering systemic therapy or surgery.