STEREOTYPIES: GENERAL BASIS, DEFINITION, AND CLASSIFICATION

Stereotypies are poor defined clinical phenomena. Their boundaries are vague, pathophysiology is mysterious, consequences are unknown and, often treatment is ineffective.

The major difficulty in defining stereotypies is the absence of specificity of the motor activity, as occurs also with tics. Any operative definition would need take in consideration non-motor aspects, such as the absence of any provocative motor or sensorial activity, the influences of the will and the capacity of control. These characteristics may be more useful clinical indices than the movements themselves.

Motor (act/ activity/ behaviour...), non-functional (non-goal directed/purposeless) and, repetitive (similar) are the terms more usually used in the various definitions. Interestingly, such words as non reflex (induced by inner sensory stimulus), coordinated (patterned), rhythmic, unvoluntary (involuntary) are frequently but not always used in their definition. Because the usual definitions of stereotypies are disparate and can be applied to other abnormal movements, such as tics, a consensus for an unambiguous definition would be necessary.

Concerning classification different axis must be considered such as transient or chronic; axial, extremities or generalized; but the most important classification is based on their aetiology: primary (or essential) that includes the so called physiologic and secondary (or symptomatic) that includes stereotypies encountered in children in the setting of mental retardation, pervasive developmental disorders (autism), and a variety of psychiatric, metabolic or neurodegenerative disorders.