Dyskinesia is characterized by complex, irregular involuntary movements involving lips, tongue, extremities, and/or trunk. The term “dyskinesia” is often used to encompass complex involuntary movements that do not fit into another category of involuntary movements. Focal dyskinesia is commonly seen in the lips and tongue (orolingual dyskinesia or oral dyskinesia). Drug side effects are the most common cause of generalized dyskinesia, usually those that influence dopamine such as L-dopa and neuroleptics (drug-induced dyskinesia, tardive dyskinesia). Motor stereotypies are repetitive occurrences of the same movements; movements commonly encountered in this condition range from simple movements like shaking arms and nodding to complex movements. Motor stereotypies are commonly observed in children with Asperger syndrome, Rett syndrome and other automatisms, and mental retardation. In adults, stereotyped movements are seen in cases of severe infectious encephalitis, autoimmune encephalitis (e.g., limbic encephalitis), cerebrovascular diseases involving the frontal lobe, and neurodegenerative diseases like frontotemporal lobar degeneration. Tics are irregular, typically brisk movements ranging from shock-like simple movements resembling myoclonus (simple tic) to complex movements (complex tic). Patients with tics tend to repeat certain movements like blinking or grimacing, but in the patients with Gilles de la Tourette syndrome, tics appear as a variety of movements including vocalization (vocal tic). These patients can stop the movements for several seconds, but it is often followed by rebound; they often feel an urge to move before a bout of tics and feel release after the bout.
