In order to meet the criteria for diagnosis with Stereotypic Movement Disorder children's odd motor behaviors must interfere with their ability to participate in normal developmentally appropriate activities such as school, or they must be dangerous enough that children will injure themselves if not restrained. The odd, repetitive movements must not be caused by another more appropriate diagnosis, such as Obsessive-Compulsive Disorder, or by a pervasive developmental disorder such as Autism.
Stereotypic Movement Disorder is not very common in the general population of children and adolescents. It is a fairly common occurrence within the population of Mentally Retarded population, however. To a lesser extent, the behavior is also more common in populations of sensory disabled children, such as blind children. According to the DSM, between 2 and 3% of retarded children (who are capable of living in the community) engage in stereotyped motor behavior. A far larger percentage of the severely retarded population (up to 25%!) are diagnosed with Stereotypic Movement Disorder. Head-banging is the most commonly acted out self-injurious behavior.
Diagnosis of Stereotyped Movement Disorder
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The compulsive, repetitive and nonfunctional movement behaviors characteristic of Stereotyped Movement Disorder are not at all subtle, and point quickly to a small group of diagnoses only. The assessment task set before diagnosing clinicians is to determine which diagnoses best fit the child's unique circumstances. In order to make the necessary differentiations, clinicians will generally gather as much historical information as they can as well as conduct interviews and behavioral observations of the child's behavior. Historical information helps clinicians to understand how the movement symptoms first developed and how they may have changed over time. Current observational and interview data helps the clinician determine frequency (whether the behaviors are constant or intermittent), triggers (do they occur during particular events or situations), and consequences (how the behaviors influence parents, family members and peers).
When practical, interviews and observations should be conducted in both home and school settings to determine whether the child behaves differently in one context versus another. Interviews may utilize a structured format such as the Child Behavior Checklist so that important questions are not missed. Interview data may be supplemented with information from tests such as the Personality Inventory for Children (PIC). The PIC measures the developmental, emotional, personality, interpersonal (social), and cognitive (mental) status of children and adolescents. The test yields measures of Hyperactivity, Conduct Problems, and Social Skills Deficits in children between the ages of 5 (kindergarten) and 19 (senior year of high school) years.
As is the case with most mental illnesses, it is a good idea that a complete medical exam be conducted on children who are suspected of having Stereotypic Movement Disorder so that underlying medical causes of such behavior can be either identified and treated, or ruled out.
Clinicians use the observational, interview, medical, and historical information they've gathered to figure out whether Stereotyped Movement Disorder best accounts for the child's presentation, or whether some other diagnosis applies. There are multiple diagnoses characterized by self-injurious behavior, and Stereotyped Movement Disorder needs to be differentiated from these conditions. For instance, individuals with Borderline Personality Disordered will sometimes cut or burn themselves. In this example, Borderline cutting and burning behavior is intentionally self-inflicted (as a punishment or as a means of feeling an intense sensation) making it different in quality from the self-injurious behavior characteristic of Stereotyped Movement Disorder. Additionally, Borderline Personality is a syndrome in its own right with a characteristic set of symptoms which also must be present before that diagnosis can apply.
Readers may also note that Stereotyped Motor Disorder are similar in quality to Tic Disorders such as Tourette's Syndrome (click here to return to our earlier discussion of these disorders.. Both conditions have as their primary symptom an irresistible compulsion to act out seemingly nonfunctional and meaningless behaviors. The conditions are differentiated on the basis of one being a motor disorder, involving body movements, while the other is often verbal in nature. There is such a thing as complex motor tics, of course, and it can be difficult to correctly know when stereotyped behaviors should be thought of as motor tics rather than a movement disorder.