Understanding Myokymia in Simple Terms
Myokymia is caused by abnormal, spontaneous electrical activity in the nerves that control your muscles, making small groups of muscle fibers contract repeatedly on their own—like a "short circuit" in the nerve's wiring that causes the muscle to twitch continuously. 1
What's Actually Happening
Think of your nerves as electrical wires that send signals to your muscles. In myokymia, something disrupts the normal function of these nerve "wires," causing them to fire off signals repeatedly without you wanting them to 1. This creates:
- Visible rippling or worm-like movements under the skin, as if something is crawling beneath the surface 2, 3
- Continuous muscle twitching that you can't control, lasting several seconds at a time 3
- The affected muscle keeps contracting in bursts, several times per second, creating that characteristic undulating appearance 1
Why Does This Happen?
The nerve membrane becomes overly excitable due to changes in its chemical environment 1. Specifically:
- The biochemical balance around the nerve gets disrupted, particularly involving calcium levels in the fluid surrounding the nerve 1
- This makes the nerve membrane "jumpy" and prone to firing signals spontaneously 1
- The nerve essentially becomes hypersensitive and starts sending muscle contraction signals on its own 1
Common Triggers and Causes
Myokymia can be triggered by various conditions that affect nerve function 2, 1:
- Autoimmune conditions like multiple sclerosis or Guillain-Barré syndrome, where the body's immune system affects the nerves 2, 1
- Medications, particularly gold salts used for rheumatoid arthritis 3
- Radiation damage to nerve bundles 1
- Genetic mutations in potassium channels (the "gates" that control electrical flow in nerves), causing hereditary forms 4
- Thyroid problems affecting metabolism 2
- Brain or spinal cord lesions affecting nerve pathways 1
Where It Occurs
- Facial myokymia is most common, affecting muscles around the eyes and face 1
- Limb myokymia affects arms and legs 2, 1
- Can sometimes involve widespread muscle groups throughout the body 5
Key Distinction
Unlike a simple muscle twitch (fasciculation) that happens once and stops, myokymia involves repeated, rhythmic bursts of contractions that create that characteristic rippling appearance—the difference is like comparing a single hiccup to continuous hiccupping 3, 1.