A spasm is a sudden tightening of your muscles, which you cannot control. A muscular spasm in the coronary artery can cause a heart attack A lack of magnesium causes muscles to go into spasm. = convulsion
A sudden, involuntary contraction of a muscle or group of muscles In the esophagus, this results in a strong, uncoordinated, non-propulsive contraction which leads to dysphagia and chest pain