Superior Oblique Myokymia
Definition
Uniocular paroxysms of small-amplitude, high-frequency rotary nystagmus.
Etiology
- Unknown.
- May be regeneration of damage to trochlear nerve as it has been described in two patients who had superior oblique palsy. Arch Ophth Link
- If there are other neurological symptoms there could be a tumor compressing the midbrain.
Clinical Features
Patient History
- Intermittent bursts of torsional and/or vertical diplopia or “shimmering” vision.
- Episodes last several seconds to several minutes
- Fatigue and stress may exacerbate
Exam
- Rapid small-amplitude torsional eye movement, may only be seen at the slit lamp
- Normal eye movements in absence of symptoms
Work Up
None unless other neurologic signs then consider neuroimaging
Treatment
None if the patient is not bothered
Medical Treatment
- topical betaxolol (Betoptic 0.5%, Betoptic S 0.25%) BID- one report of success
- carbamazepine (tegretol) 100 mg BID or TID to start and move to up to 200 mg TID as needed
- potential side effects including leucopenia, acute renal failure, thromboembolism, and arrhythmias
- blood counts (CBC, including platelets and reticulocytes), serum iron, liver function and renal function (urinalysis an BUN) needed to be monitored regularly
- gabapentin 100mg QD or BID can titrate up to 300mg PO BID
- propranolol 80 mg long acting
- phenytoin (dilantin) 100mg PO TID
- propranolol plus valproic acid
- Medical treatment is often disappointing and fraught with side effects
Surgical Treatment
- Tenectomy of Superior Oblique- a large portion needs to be removed
- Combine above with prophylactic inferior oblique weakening
- Some require a second surgery to treat residual diplopia with recession of contralateral inferior rectus with a nasal shift and possibly a nasal shift of both inferior rectus muscles if there is excyclotorsion