This rare condition is characterized by bursts of small amplitude, high frequency torsional oscillations of one eye due to superior oblique contraction. This results in symptoms of intermittent vertical or torsional diplopia, monocular blurring of vision, and tremulous sensations in the eye that usually last less than 10 seconds and occur many times per day1.
The abnormal movements may occur either spontaneously or immediately after a downward eye movement or blinking.
Eye movement recordings have demonstrated initial intorsion and depression followed by irregular small oscillations2.
On examination, the oscillation can be very subtle and observation with an ophthalmoscope when the patient is looking ‘‘down and in’’ may be required; alternatively, fixing on a conjunctival vessel may be of value.
Pathogenesis
Neurovascular compression of the trochlear nerve, typically by the posterior cerebral or superior cerebellar arteries at the root entry zone3.
Superior oblique myokymia may be associated with MS, posterior fossa tumor, stroke, or trauma.
Treatment
Superior oblique myokymia is usually benign and sensitive to small doses of gabapentin or carbamazepine.
(If drug treatment fails, surgical procedures such as superior oblique tenectomy with myectomy of the ipsilateral inferior oblique muscle are available.)
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From: Lenci MT, Thurtell MJ. Vertical Oscillopsia: A Case of Superior Oblique Myokymia. EyeRounds.org Derived from: https://webeye.ophth.uiowa.edu/eyeforum/atlas-video/SOM.htm