Superior Oblique Myokymia
Superior oblique myokymia is a rare entity whose cause is poorly understood. Some evidence indicates that it is caused by ephaptic transmission between fourth cranial nerve fibers perhaps due, in some cases, to damage by vascular compression.
In superior oblique myokymia, there are abnormal torsional movements of the eye that cause diplopia and monocular oscillopsia. Usually, patients are otherwise neurologically normal. Recurrences may persist indefinitely.
Treatment is not necessary if the patient is not disturbed by the visual symptoms. Various systemic medications (such as carbamazepine, phenytoin, propranolol, baclofen, gabapentin) and topical timolol have produced inconsistent results but have been advocated as first-line treatment because some patients will benefit, at least in the short term. Effective surgical treatment requires that the superior oblique muscle be disconnected from the globe by generous tenectomy. Because this typically results in a superior oblique palsy, some surgeons perform simultaneous inferior oblique muscle weakening.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.