Superior Oblique Myokymia

Superior oblique myokymia (SOM) is a rare condition characterized by intermittent, involuntary contractions of the superior oblique muscle in one eye. These brief episodes cause the affected eye to make small, rapid rotational movements, resulting in a shimmering, jiggling, or bouncing sensation in vision.

Understanding Superior Oblique Myokymia

The superior oblique muscle rotates the eye and helps with looking down and inward. In SOM, this muscle contracts spontaneously and rapidly in brief bursts. The cause is thought to be abnormal nerve signals or compression of the fourth cranial nerve, similar to how some people develop facial twitching from nerve compression.

Symptoms

Visual Symptoms

Oscillopsia

• Visual world appears to shimmer, jiggle, or bounce
• Brief episodes lasting seconds
• Can occur many times per day
• Usually only one eye affected

Monocular diplopia/torsion

• May perceive tilting or rotation of images
• Vertical component possible

When Symptoms Occur

• Often triggered by looking down
• May occur spontaneously
• Can be triggered by fatigue or stress
• Episodes typically brief (few seconds)

What Patients Describe

• "My vision shimmers"
• "Things jiggle briefly"
• "I see double momentarily"
• "My eye feels like it's vibrating"

Diagnosis

Clinical Examination

Observation of eye during episode:

• Small, rapid rotational/vertical movements
• Intorsion (top of eye rotates toward nose)
• Usually subtle—may need careful observation
• May need to look at conjunctival vessels to see movement

Triggers

• Ask patient to look down
• Stress, fatigue may provoke
• Patient can often tell when episode is happening

Imaging

• MRI brain may be considered
• Rarely shows vascular compression
• Often normal
• Done mainly to rule out other pathology

Differential Diagnosis

• Nystagmus
• Ocular flutter
• Myokymia of other muscles

Treatment

Medications (First-Line)

Carbamazepine or oxcarbazepine

• Often very effective
• Low doses usually sufficient
• Similar to treatment for trigeminal neuralgia
• Side effects: dizziness, drowsiness, blood count changes

Other options:

• Gabapentin
• Baclofen
• Beta-blockers (less common)

Observation

• Some cases are mild enough to tolerate
• May have periods of remission
• Not dangerous if untreated

Surgical Options (Rarely Needed)

Superior oblique tenectomy/tenotomy

• Weakens the muscle
• Reserved for medication failures
• Effective in most surgical cases

Microvascular decompression

• If vascular compression identified
• Rarely performed
• Potentially curative

Living with SOM

Practical Tips

• Identify and avoid triggers if possible
• Adequate sleep
• Stress management
• May need to take breaks during visually demanding tasks

Impact on Daily Life

• Usually manageable with medication
• Episodes are brief
• Does not damage vision
• Most people function well

Prognosis

Generally Good

• Responds well to medication in most cases
• Benign condition—no threat to vision or health
• May wax and wane
• Some cases resolve spontaneously

Long-Term

• Chronic condition for most
• May need long-term medication
• Surgery effective if medication fails

Frequently Asked Questions

Is this dangerous to my eye?

No. SOM is annoying but not dangerous. It doesn't damage the eye or cause permanent vision problems. The episodes are brief, and the condition is manageable with treatment.

Why does this happen?

The exact cause isn't always clear. It may be due to abnormal signals in the fourth cranial nerve or, rarely, compression of the nerve by a blood vessel. Sometimes no cause is found.

Will medication help?

Yes, in most cases. Carbamazepine or similar medications are effective for many patients, often at low doses. If one medication doesn't work, others can be tried.

Is this related to the twitching I feel in my eyelid?

No. Eyelid myokymia (the common benign lid twitch most people experience) is different from superior oblique myokymia. SOM affects an eye movement muscle, not the eyelid, and causes oscillopsia rather than just a twitching sensation.

Do I need surgery?

Usually not. Most patients do well with medication. Surgery is reserved for cases that don't respond to medication or where medication isn't tolerated.

References