Obsessive-compulsive and related disorders. Stereotypic movement disorder is dis-
tinguished from obsessive-co mpulsive disorder (OCD) by the absence of obsessions, as
well as by the nature of the repetitive behaviors. In OCD the individual feels driven to per-
form repetitive behaviors in response to an ob session or according to rules that must be ap-
plied rigidly, whereas in stereotypic movement disorder the behaviors are seemingly
driven but apparently purposeless. Trichot illomania (hair-pulling disorder) and excoria-
tion (skin-picking) disorder are characterize d by body-focused repetitive behaviors (i.e.,
hair pulling and skin picking) that may be seemingly driven but th at are not apparently
purposeless, and that may not be patterned or rhythmical. Furthermore, onset in tricho-
tillomania and excoriation disord er 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, pa roxysmal dyskinesias, and benign he-
reditary chorea. A neurological history and examination are required to assess features
suggestive of other disorders, such as myoclo nus, dystonia, tics, and chorea. Involuntary
movements associated with a neurological co ndition 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 type s of movements do not result
in self-injury. A diagnosis of stereotypic mo vement disorder is not appropriate for repet-