Twitching and spasm of the muscles, most frequently in the feet and hands , although the muscles of the face, larynx (voicebox), or spine can also be affected. The spasms are caused by a biochemical disturbance and are painless at first; if the condition continues, the spasms tend to becoming increasingly painful.
Muscle damage can result if the cause is not dealt with. The most widespread underlying is hypocalcaemia (a low level of calcium in the blood). Other causes include hypokalaemia (a low level of potassium) , hyperventilation during a panic attack, or, more unusually hyperparathyroidism (underactivity of the parathyroid glands).