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Ivan Donaldson

, C. David Marsden

, Susanne A. Schneider

, and Kailash P. Bhatia

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date: 20 May 2022

The concept of tics defies precise or concise definition. In its simplest form it may be defined as a rapid brief repetitive purposeless movement, occurring at irregular intervals. Sometimes the movement may be slow and sustained (‘dystonic’ or ‘tonic tic’) as opposed to more common fast action (‘clonic tic’) (Jankovic and Fahn 1986 , Jankovic 1992). As applied to simple tics involving a muscle or group of muscles, such definition may be adequate. These movements usually involve contraction of agonists and antagonists and even an apparently simple movement, such as a shoulder shrug, may involve many muscles, each activated in an orderly sequence. The concept of tics, however, extends to embrace more complicated stereotyped patterns of activity such as turning in circles, retracing steps, and squatting. Such actions involve even greater complexity of motor integration and last much longer. In addition, noises produced in the nasal cavity, mouth, throat, or larynx are included as tics. The simplest consist of unintelligible sounds, but the more complex involve intelligible speech, requiring a degree of organization similar to the more complicated motor tics. Unfortunately there is no general agreement about the precise classification of these more complex motor and vocal acts. While they are regarded here as tics others have considered them as associated obsessive-compulsive activity (Frankel et al. 1986).

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