Normal development. Simple stereotypic movements are common in infancy and early childhood. Rocking may occur in the transition from sleep to awake, a behavior that usu- ally resolves with age. Complex stereotypies are less common in typically developing children and can usually be suppressed by distraction or sensory stimulation. The indi- vidual’s daily routine is rarely affected, and the movements generally do not cause the child distress. The diagnosis would not be appropriate in these circumstances.
Autism spectrum disorder. Stereotypic movements may be a presenting symptom of haviors are being evaluated. Deficits of social communication and reciprocity manifesting in autism spectrum disorder are generally absent in stereotypic movement disorder, and thus social interaction, social communication, and rigid repetitive behaviors and interests are distinguishing features. When autism spectrum disorder is present, stereotypic move- ment disorder is diagnosed only when there is self-injury or when the stereotypic behav- iors are sufficiently severe to become a focus of treatment.
Tic disorders. Typically, stereotypies have an earlier age at onset (before 3 years) than do tics, which have a mean age at onset of 5—7 years. They are consistent and fixed in their pattern or topography compared with tics, which are variable in their presentation. Ste— reotypies may involve arms, hands, or the entire body, while tics commonly involve eyes, face, head, and shoulders. Stereotypies are more fixed, rhythmic, and prolonged in dura- tion than tics, which, generally, are brief, rapid, random, and ﬂuctuating. Tics and stereo— typic movements are both reduced by distraction.
Obsessive-compulsive and related disorders. Stereotypic movement disorder is dis- tinguished from obsessive-compulsive disorder (OCD) by the absence of obsessions, as well as by the nature of the repetitive behaviors. In 0CD the individual feels driven to per- form repetitive behaviors in response to an obsession or according to rules that must be ap- plied rigidly, whereas in stereotypic movement disorder the behaviors are seemingly driven but apparently purposeless. Trichotillomania (hair-pulling disorder) and excoria- tion (skin-picking) disorder are characterized by body-focused repetitive behaviors (i.e., hair pulling and skin picking) that may be seemingly driven but that are not apparently purposeless, and that may not be patterned or rhythmical. Furthermore, onset in tricho- tillomania and excoriation disorder is not typically in the early developmental period, but rather around puberty or later.
Other neurological and medical conditions. The diagnosis of stereotypic movements requires the exclusion of habits, mannerisms, paroxysmal dyskinesias, and benign he- reditary chorea. A neurological history and examination are required to assess features suggestive of other disorders, such as myoclonus, dystonia, tics, and chorea. Involuntary movements associated with a neurological condition may be distinguished by their signs and symptoms. For example, repetitive, stereotypic movements in tardive dyskinesia can be distinguished by a history of chronic neuroleptic use and characteristic oral or facial dyskinesia or irregular trunk or limb movements. These types of movements do not result in self-injury. A diagnosis of stereotypic movement disorder is not appropriate for repet- itive skin picking or scratching associated with amphetamine intoxication or abuse (e.g., patients are diagnosed with substance/medication-induced obsessive-compulsive and re- lated disorder) and repetitive choreoathetoid movements associated with other neurolog- ical disorders.
Stereotypic movement disorder may occur as a primary diagnosis or secondary to another disorder. For example, stereotypies are a common manifestation of a variety of neuro- genetic disorders, Such as Lesch-Nyhan syndrome, Rett syndrome, fragile X syndrome,