The cause of dystonia is not known. Researchers believe that dystonia results from an abnormality in or damage to the basal ganglia or other brain regions that control movement. There may be abnormalities in the brain’s ability to process a group of chemicals called neurotransmitters that help cells in the brain communicate with each other.  There also may be abnormalities in the way the brain processes information and generates commands to move.  In most cases, no abnormalities are visible using magnetic resonance imaging or other diagnostic imaging.

One way to classify the dystonias is based upon the regions of the body which they affect:

• Generalized dystonia affects most or all of the body.
• Focal-dystonia is localized to a specific part of the body.
• Multifocal-dystonia involves two or more unrelated body parts.
• Segmental-dystonia affects two or more adjacent parts of the body.
• Hemidystonia involves the arm and leg on the same side of the body.

Primary dystonia is used to describe a case in which the dystonia is the predominant symptom, and the person is not affected by other neurological conditions. Secondary dystonia refers to dystonia that is associated with a known outside factor or condition (such as trauma, drug exposure, stroke, cerebral palsy, and others).