[Superior oblique myokymia: a report of three cases]

Abstract

Introduction: Superior oblique myokymia (SOM/MOS) is an under-recognised and probably under-diagnosed disorder. We describe the clinical signs of this condition among three patients. Next, from review of the literature, we suggest an algorithm for diagnosis and treatment.

Observation: Retrospective study of three patients aged 40 to 55 presenting with brief, intermittent monocular episodes of oscillopsia.

Discussion: The acute symptomatology of superior oblique myokymia follows a recognizable pattern: it always presents with brief, intermittent monocular vertical oscillopsia and/or vertical diplopia with torsion. The clinical signs are related to a neurogenic hyperexcitability of the superior oblique muscle. Treatment may be medical (carbamazepine, gabapentin, beta-blocker) or surgical. Recent publications report that superior oblique myokymia may result from vascular compression of the trochlear nerve (fourth cranial nerve), which controls the action of the superior oblique muscle, placing this condition in the category of vasculonervous conflicts.

Conclusion: Superior oblique myokymia is a relatively poorly known disorder, despite classic pathognomonic symptoms. It is a benign condition, which can nonetheless become incapacitating. It occasionally portends an intracranial pathologic process, which must then be addressed with specific treatment.