Although they both involve involuntary contractions of muscle tissue, muscle twitches and muscle spasms are different conditions with different causes, according to the University of Maryland Medical Center. Muscle twitches, also called fasciculations, usually only affect a single muscle. They're characterized by tiny contractions inside the muscle, caused by a nerve impulse. Muscle spasms, also called muscle cramps, affect multiple muscle tissues and are brought on by a chemical imbalance in the body.
Common Causes of Muscle Twitches
Twitching of the eyelids, thumb or calf muscles in the legs are common and, according to the University of Maryland Medical Center, caused by anxiety or stress. This benign twitching comes and goes, usually not lasting for more than a few days. Muscle fatigue from overexercise, caffeine and side effects from medications can also cause twitching. According to FibromyalgiaSymptoms.org, muscle twitching is often associated with symptoms such as sleep disorders, tingling and a feeling as if your muscles are "electric."
Rare Causes of Muscle Twitches
Disorders of the nervous system can also cause muscles to twitch. These include nerve damage, fibromyalgia, muscular dystrophy and Lou Gehrig's disease. Along with muscle twitching, weakness in the muscles accompanies these disorders.
Common Causes of Muscle Spasms
Muscle spasms make the affected muscle group feel hard and bulging. The cramps are most often brought on by heavy exercise, dehydration, excess alcohol use, pregnancy, medications or reduced levels of calcium or magnesium in the body.
Rare Causes of Muscle Spasms
Conditions such as hypothyroidism and kidney failure can also cause muscle spasms. According to the American Medical Association, brain damage due to head injuries, cerebral palsy, stroke and Parkinson's disease can cause abnormal rigidity in muscles. Other causes include pressure on a nerve from disk problems in the spine.
Relief From Muscle Twitches and Spasms
Gently stretching and massaging the affected muscle can help reduce twitching. Walking or using the affected muscle is another way to find relief. Gentle, slow stretching also works for muscle spasms. The University of Maryland Medical Center recommends seeing a doctor if muscle spasms are a recurring problem.