What causes a muscle spasm?
There are a variety of causes of muscle spasms, and each depends upon predisposing factors, the part of the body involved, and the environment the body is working in.
Spasms may occur when a muscle is overused and tired, particularly if it is overstretched or if it has been held in the same position for a prolonged period of time. In effect, the muscle cell runs out of energy and fluid and becomes hyperexcitable and then develops a forceful contraction. This spasm may involve part of a muscle, the whole muscle, or even adjacent muscles.
Overuse as a cause of skeletal muscle spasm is often seen in athletes who are doing strenuous exercise in a hot environment. This is also an occupational issue with construction workers or others working in a hot environment. Usually, the spasms will occur in the large muscles that are being asked to do the work.
Overuse can also occur with routine daily activities like shoveling snow, or mowing or raking grass causing muscle spasms of the neck, shoulder, and back.
Unfamiliar exercise activities can also cause muscle spasms to occur. Abdominal spasms can occur when a person decides to begin working their abdominal muscles by doing situps and does too many too quickly.
Writer's cramps are similarly caused by prolonged use of the small muscles in the hand.
It is commonly thought that dehydration and depletion of electrolytes will lead to muscle spasm and cramping. Muscle cells require enough water, glucose, sodium, potassium, calcium, and magnesium to allow the proteins within them to interact and develop an organized contraction. Abnormal supply of these elements can cause the muscle to become irritable and go into spasm.
Atherosclerosis or narrowing of the arteries (peripheral artery disease) may also lead to muscle spasm and cramps, again because adequate blood supply and nutrients are not able to be delivered to the appropriate muscle. Peripheral artery disease can decrease the flow of blood to the legs causing pain with activity. There may also be associated muscle cramps.
Leg spasms are often seen related to exercise, but cramps may also be seen at night involving calf and toe muscles. Nocturnal leg cramps and restless legs syndrome are considered a type of sleep disturbance.
Systemic illnesses like diabetes, anemia (low red blood cell count), kidney disease and thyroid and other hormone issues are also potential causes of muscle spasms.
Diseases of the nervous system, such as multiple sclerosis or spinal cord injury, can be associated with muscle spasm.
Smooth muscle can also develop spasm. When a hollow structure filled with air or fluid is squeezed by the muscle spasm, significant pain can occur since the fluid or air cannot be compressed. For example, smooth muscle in the intestinal wall can go into spasm, causing waves of pain called colic. Colicky pain which tends to be rhythmic (coming and going) may also occur within the bile duct that empties the gallbladder and may develop after eating.
- When kidney stones try to pass, the smooth muscles that are in the walls of the ureter that connect the kidney to the bladder, may spasm and cause significant pain. Often this type of pain is associated with nausea and vomiting.
- Muscles that surround the esophagus can go into spasm when irritation occurs with reflux esophagitis or GERD.
- Diarrhea can be associated with colicky pain, whereby the muscles within the colon wall spasm just before a watery bowel movement.
Dystonias are movement disorders where groups of muscles forcefully contract causing twisting and repetitive movements or the inability to have a normal posture as a result of muscle spasm and cramping. The symptoms may be very mild initially but gradually progress to become more frequent and aggressive. Occasionally, there is no progression. Examples of this type of muscle spasm include torticollis (where the neck muscles spasm and cause the head to turn to one side), blepharospasm (where there is uncontrolled blinking of the eyes), and laryngeal dystonia that affects the muscles that control speech. Dystonias may be caused by abnormally functioning neurotransmitter chemicals in the part of the brain called the basal ganglia. These chemicals (serotonin, dopamine, acetylcholine, and GABA) are required to properly send messages that begin muscle contraction. Dystonia symptoms may occur as a complication of stroke.