Muscle spasm

A muscle spasm is a sudden, involuntary contraction of a muscle or group of muscles that can be brief or sustained.

Spasms range from a fleeting twitch to a painful cramp that locks a muscle for minutes, most often in the calf, foot, hamstring or back. Common triggers include overuse, dehydration, electrolyte imbalance, prolonged sitting and nerve irritation from a disc problem. Spasms that occur repeatedly or are accompanied by weakness may reflect an underlying neurological condition, in which case sustained stiffness is more often described as spasticity.

Evaluation begins with the pattern, location and triggers, followed by a physical examination; blood tests or nerve studies are added when a systemic or neurological cause is suspected. Most occasional spasms are benign. Cannabinoids have been studied for spasticity in multiple sclerosis, and research on ordinary muscle spasms is limited.