Spasm

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A spasm is a sudden involuntary contraction of a muscle;^[1] a group of muscles; or a hollow organ, such as the bladder.

A spasmodic muscle contraction may be caused by many medical conditions, including dystonia. Most commonly, it is a muscle cramp which is accompanied by a sudden burst of pain. A muscle cramp is usually harmless and ceases after a few minutes. It is typically caused by ion imbalance or muscle overload.

There are other causes of involuntary muscle contractions, and some of these may cause a health problem.