Myokymia is characterized by spontaneous, fine fascicular contractions of muscle without muscular atrophy or weakness. Eyelid myokymia results from fascicular contractions of the orbicularis oculi muscle. Eyelid myokymia is typically unilateral, with the most common involvement being one of the lower eyelids. When multiple eyelids are involved, the fascicular contractions of each eyelid are independent of each other.
In most cases, eyelid myokymia is benign, self-limited, and not associated with any disease. Intervention is usually unnecessary. Rarely, eyelid myokymia may occur as a precursor of hemifacial spasm, blepharospasm, Meige syndrome, spastic-paretic facial contracture, and multiple sclerosis.
Consisting of involuntary fine undulating contractions across the striated muscle, the pathophysiology of eyelid myokymia is not well understood. The contractions are nonsynchronous semirhythmic discharges of motor units discharging at a rate of 3-8 Hz. The discharges have intervals of 100-200 ms between individual motor bursts. The contractions are transient and intermittent. 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 suggested. Possible precipitating factors include stress, fatigue, and excessive caffeine or alcohol intake.
The incidence and prevalence of eyelid myokymia are unknown, but symptoms of eyelid myokymia are frequently encountered in the ophthalmic clinic.
Eyelid myokymia is a benign and self-limited condition in most patients, but, in some cases, it may be a precursor of hemifacial spasm, blepharospasm, Meige syndrome, spastic-paretic facial contracture, facial myokymia, and multiple sclerosis.
Eyelid myokymia usually occurs in adults but may occur at any age.