Myokymia

 Myokymia is the spontaneous, fine fascicular contractions of muscle without muscular atrophy or weakness. Eyelid myokymia typically involves the orbicularis oculi muscle of one of the lower eyelids; occasionally, one of the upper eyelids can be affected. In most cases, eyelid myokymia is benign, self-limited, and not associated with any disease. Intervention is usually necessary. Rarely, eyelid myokymia may occur as a precursor of hemifacial spasm, blepharospasm, Meige syndrome, and spastic-paretic facial contracture. 

Pathophysiology 

The pathophysiology of typical eyelid myokymia is not well understood. The focus of irritation is most likely the nerve fibers within the muscle. Pontine dysfunction in the region of the facial nerve nucleus also has been implicated. Possible precipitating factors include stress, fatigue, and excessive caffeine or alcohol intake. 

Frequency 

United StatesThe incidence and prevalence of eyelid myokymia are unknown, but symptoms of eyelid myokymia are not infrequently encountered in the ophthalmic clinic. 

Mortality/Morbidity 

Eyelid myokymia is a benign and self-limited condition in most patients. 

Age

Eyelid myokymia may occur at any age.

• Patients with eyelid myokymia usually note sporadic "jumping" or "twitching" of one of the lower eyelids. Eyelid myokymia may also involve one of the upper eyelids. The irregular contractions are usually unilateral and may occur intermittently for days to months.
• In rare cases, the contractions may be severe enough to move the eye to produce oscillopsia.
• A history of stress, fatigue, and excessive caffeine or alcohol intake may be present.

• Fine contractions of the orbicularis oculi may be visible, if the patient has the contractions during examination. 
  • If present, the contractions are usually intermittent and are more apparent to the patient than to the observer.
  • The symptoms often improve when the eyelid is pulled manually.
  • Rarely, the contractions may be vigorous enough to cause movement of the globe, producing fine nystagmus like eye movements. 
• If the eyelid myokymia is associated with contraction of other parts of the face, hemifacial spasm, blepharospasm, Meige syndrome, and spastic-paretic facial contracture should be excluded.

Causes

The cause is unknown but may be associated with stress, fatigue, and excessive caffeine or alcohol intake. 

     taken fron: emedicine.medscape.com