Neuropathophysiology of paroxysmal, systemic, and other related movement disorders.

Movement disorders are neurological conditions affecting the ability to produce and control voluntary as well as involuntary movements, and may be categorized into akinetic/rigid and hyperkinetic disorders. The hyperkinetic disorders are generally perceived as being the most difficult to diagnose correctly. They are manifested by excessive, abnormal involuntary movements, and are referred to as dyskinesias. The conditions are further designated paroxysmal dyskinesias when the abnormal movements occur episodically, followed by a rapid return to normality without impaired consciousness between episodes. The events can be precipitated by sudden voluntary movements, or may occur spontaneously at rest, or precipitated by exertion or sleep. Most conditions are either inherited or sporadic, and some cases are associated with specific conditions. Although clinical scenarios can be confusing, considerable advances in the phenotype characterisation and genetic studies have provided important information that allowed simplifying the clinical definitions and diagnosis of the paroxysmal dyskinesias. These advances have helped understand the pathophysiology of these disorders and their variants.