Stereotypic movement disorder is a motor disorder with onset in childhood involving repetitive, nonfunctional motor behavior, that markedly interferes with normal activities or results in bodily injury. To be classified as SMD, the behavior in question must not be due to the direct effects of a substance or another medical condition. The cause of this disorder is not known.
Signs and symptoms
Common repetitive movements of SMD include head banging, arm waving, hand shaking, rocking and rhythmic movements, self-biting, self-hitting, and skin-picking; other stereotypies are thumb-sucking, nail biting, trichotillomania, bruxism and abnormal running or skipping.
Diagnosis
Stereotyped movements are common in infants and young children; if the child is not distressed by movements and daily activities are not impaired, diagnosis is not warranted. When stereotyped behaviors cause significant impairment in functioning, an evaluation for stereotypic movement disorder is warranted. There are no specific tests for diagnosing this disorder, although some tests may be ordered to rule out other conditions. SMD may occur with Lesch–Nyhan syndrome, intellectual disability, and fetal alcohol exposure or as a result of amphetamine intoxication. When diagnosing stereotypic movement disorder, DSM-5calls for specification of:
Other conditions which feature repetitive behaviors in the differential diagnosis include autism spectrum disorders, obsessive–compulsive disorder, tic disorders, and other conditions including dyskinesias. Stereotypic movement disorder is often misdiagnosed as tics or Tourette syndrome. Unlike the tics of TS, which tend to appear around age six or seven, repetitive movements typically start before age three, are more bilateral than tics, and consist of intense patterns of movement for longer runs than tics. Tics are less likely to be stimulated by excitement. Children with stereotypic movement disorder do not always report being bothered by the movements as a child with tics might.
Treatment
There is no consistently effective medication for SMD, and there is little evidence for any effective treatment. In non-autistic habit reversal training may be useful. No treatment is an option when movements are not interfering with daily life.
Prognosis
Prognosis depends on the severity of the disorder. Recognizing symptoms early can help reduce the risk of self-injury, which can be lessened with medications. Stereotypic movement disorder due to head trauma may be permanent.
Epidemiology
Although not necessary for the diagnosis, individuals with intellectual disability are at higher risk for SMD. It is more common in boys, and can occur at any age.
