Overview
Dystonia is a movement disorder in which your muscles contract involuntarily, causing repetitive or twisting movements.
The condition can affect one part of your body (focal dystonia), two or more adjacent parts (segmental dystonia) or all parts of your body (general dystonia). The muscle spasms can be mild or severe, and might interfere with your performance of day-to-day tasks.
There's no cure for dystonia. But medications can improve symptoms. Surgery is sometimes used to disable or regulate nerves or certain brain regions in people with severe dystonia.
Source: http://www.mayoclinic.com