Experts aren't exactly sure what causes dystonia. But they think it's related to a problem in the part of the brain called the basal ganglia. This is where your brain processes the information that helps your muscles contract. The theory is that your neurotransmitters, the chemicals that do the talking in the brain, are abnormal in people with dystonia. Dystonia, though, doesn't affect your intelligence or your ability to think. It isn’t generally related to mental health issues. Sometimes, dystonia can occur after taking certain kinds of medicines. This is called tardive dystonia.
Research has pinpointed a number of different genetic defects that have been linked to dystonia. Dystonia can also be caused by a stroke, head injury, or other injury to the brain. These are called forms of secondary dystonia. In this case, the symptoms may be limited to one side of the body.
The first signs of dystonia can appear at any age, from children (usually between ages 5 and 16) to adults.