Introduction

Normally, most movements are intentional (voluntary). That is, people will a movement or decide to move, even though these decisions are usually made automatically. In movement disorders, people no longer have control because areas of the brain that control movement malfunction or become damaged. Movements may occur unintentionally (involuntarily) or voluntary movements may not be made as intended. As a result, daily activities can become frustratingly difficult or impossible. Many movement disorders are progressive, eventually resulting in disability. However, they progress at different speeds, and treatments can often relieve symptoms, sometimes for a long time.

See the figure Where Damage Occurs in Movement Disorders.

The types of movements affected and the severity of the involuntary movements depend on the disorder causing them. Some disorders cause quick jerking of muscles (myoclonus). Others cause muscles to contract and stay contracted for several minutes, forcing the person into an abnormal position (a condition called dystonia). Certain drugs have side effects that can cause repeated muscle contractions (dyskinesia) or a general restlessness (akinesia), making a person unable to be still. Some disorders, such as Parkinson's disease, cause shaking (tremor).