====== 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. [[http://archopht.ama-assn.org/cgi/reprint/102/8/1178|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|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|gabapentin]] 100mg QD or BID can titrate up to 300mg PO BID  
  * [[propranolol|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

{{tag>strabismus}}