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January 30, 2013
The term myokymia was introduced in 1894 and is derived from the Greek word kyma, meaning wave. The clinical phenomenon refers to the undulation of muscles that appear “worm–like” beneath the skin. Myokymic discharges are the accompanying electrophysiological abnormality. Myokymic discharges are brief, regular bursts of single motor unit potentials that may appear as doublets or triplets, with intervening periods of electrical silence. Myokymia is a disorder of the motor unit and a result of hyperexcitability of axons. Alterations of voltage gated potassium channels have been implicated in the underlying pathophysiology. Focal myokymia of the facial nerve can occur due to pontine glioma, multiple sclerosis, or Guillain–Barre syndrome. Additional disorders that can produce myokymia are radiation, autoimmune and paraneoplastic processes, chronic inflammatory demyelinating polyneuropathy, and toxic effects.
Submitted by: Jennifer E. Fugate, D.O.
Disclosure: Dr. Fugate served on the editorial team for the Neurology® Resident and Fellow Section.
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