RT Book, Section A1 Apetauerova, Diana A2 Rudolph, Colin D. A2 Rudolph, Abraham M. A2 Lister, George E. A2 First, Lewis R. A2 Gershon, Anne A. SR Print(0) ID 7058256 T1 Chapter 566. Movement Disorders, Tics, and Tourette Syndrome T2 Rudolph's Pediatrics, 22e YR 2011 FD 2011 PB The McGraw-Hill Companies PP New York, NY SN 978-0-07-149723-7 LK accesspediatrics.mhmedical.com/content.aspx?aid=7058256 RD 2024/03/28 AB Movement disorders are defined as either a loss or poverty (akinesia) or slowness (bradykinesia) of movement that is not associated with weakness or an excess of abnormal involuntary movements. Based on this, movement disorders are classified as either hypokinetic (Parkinsonism) or hyperkinetic (tremor, dystonia, chorea, tics, myoclonus). Movement disorders are generally caused by abnormalities in basal ganglia and their connections. The basal ganglia are that group of gray matter nuclei lying deep within the cerebral hemispheres (caudate, putamen, and pallidum), the diencephalon (subthalamic nucleus), and the mesencephalon (substantia nigra). The causes of many movement disorders remain unknown, in others various causes have been identified ranging from environmental toxins, genetic causes, medications, metabolic disorders, structural lesions, neurodegenerative causes, infectious, postinfectious causes, and autoimmune and psychogenic causes. More recent genetic, biochemical, and functional imagine advances have provided additional information about the pathophysiology and etiology of some movement disorders. Many diseases have now been localized to a specific gene (PD, dystonia, ataxia, paroxysmal dyskinesia, etc); several inherited movement disorders are due to expanded repeats of the trinucleotide cytosine-adenosine-quanosine (CAG) such as Huntington disease, some spinocerebellar ataxias (SCAs), and Dentatorubral and Pallidoluysian Atrophy (DRPLA).