Myokymia is an involuntary, spontaneous, wave-like, undulating, flickering movement within a muscle (cf. fasciculation); it may be likened to a "bag of worms."
Electrophysiologically this corresponds to regular groups of motor unit discharges, of peripheral nerve origin. Myokymia is thus related to neuromyotonia and stiffness, since there may be concurrent impairment of muscle relaxation and a complaint of muscle cramps.
A syndrome of superior oblique myokymia is described, often following superior oblique palsy, which produces a microtremor of the eye and causes oscillopsia or transient diplopia. Facial myokymia is a rare facial dyskinesia, possibly related to disinhibition of the facial
(VII) nerve nucleus by focal pontine lesions (tumor, demyelination).
Thompson PD. Stiff people. In: Marsden CD, Fahn S (eds.).
Movement disorders 3. Boston: Butterworth, 1994: 373-405