Muscle twitches are fine movements of a small area of muscle.

Muscle twitching is caused by minor muscle contractions in the area, or the uncontrollable twitching of a muscle group that is served by a single motor nerve fiber or filament.

Muscle twitches are minor and often go unnoticed. Some are common and normal. Others are signs of a nervous system disorder.

• Diet deficiency
• Drug overdose (caffeine)
• Drug side effect (such as from diuretics, corticosteroids, or estrogens)
• Exercise
• Twitches not caused by disease or disorders (benign twitches)
  • Often affecting the eyelids, calf, or thumb
  • Normal and quite common, often triggered by stress or anxiety
  • Come and go, and do not last for more than a few days

Nervous system conditions that can cause muscle twitching:

• Amyotrophic lateral sclerosis (ALS - Lou Gehrig's disease)
• Damage to the nerve that leads to a muscle
• Muscular dystrophy
• Spinal muscular atrophy
• Weak muscles (myopathy)

Symptoms that suggest a nervous system disorder include:

• Loss of, or change in sensation
• Loss of muscle size (wasting)
• Weakness