Dystonia is a neurological movement disorder. Faulty signals from the brain cause muscles to spasm and pull on the body incorrectly. This forces the body into twisting, repetitive movements or abnormal postures. Sometimes the symptoms are accompanied by dystonic tremor.

Symptoms in all dystonic conditions can vary. In many cases, if dystonia develops in childhood, it may spread to other parts of the body, and can become generalised. However, when it develops in adults, it usually confines itself to one part of the body (focal dystonia). If it spreads - which does occur in a minority of cases - it will usually affect only one other area.