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

There is usually no treatment necessary for benign muscle twitching.

Call your health care provider if you have long-term or persistent muscle twitches.

Your health care provider will take a medical history and perform a physical examination.

Medical history questions may include:

• When did you first notice the twitching?
• How long does it last?
• How often do you experience twitching?
• What muscles are affected?
• Is it always in the same location?
• Are you pregnant?
• What other symptoms do you have?

Diagnostic tests vary depending on the suspected cause. Tests may include:

• Blood tests to look for problems with electrolytes, thyroid gland function, and blood chemistry
• Electromyogram
• Nerve conduction studies
• MRI of the spine, and sometimes of the brain

Barohn RJ. Muscle diseases. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 447.