Overview of common movement disorders.

Movement disorders are a diverse group of hypokinetic and hyperkinetic neurologic diseases characterized by abnormal function of the basal ganglia. In this chapter, we will discuss the four most common diagnoses encountered in subspecialty movement disorders clinics: Parkinson disease, essential tremor, dystonia, and spasticity. The presentation and natural history of each of these disorders varies widely in terms of age of onset, anatomic distribution, and severity. We will review the demographics, clinical characteristics, diagnostic criteria, natural history, and management of these diseases. The medical and surgical management of Parkinson disease will be covered in the chapters "Update on the Medical Management of Parkinson Disease" and "Deep Brain Stimulation in Movement Disorders," respectively.