What is Stereotypic Movement Disorder?
Stereotypic movement disorder (SMD) is usually a childhood behavioral disorder, characterized by common repetitive movements, including hand waving, thumb sucking, hand biting, body rocking, head banging, among others. These abnormal movements are more common in boys than girls and usually occur within the first 3 years of life. Stress, boredom, excitement, frustration, or exhaustion can aggravate the condition. These types of abnormal behavior are unintentional and purposeless, which can actually cause physical injury to the child.
As per the 5 revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), SMD is classified under the category of neurodevelopmental disorders, as a motor (movement) disorder. Simple stereotypic movements such as rocking are quite common in normal infants, which should not be confused with SMD. However, complex stereotypic movements are far less common and typically occur in only about 3-4% of children. These types of motor stereotypies are often associated with intellectual disabilities or neurodevelopmental conditions, but can also occur in normal children.
The exact cause of this disorder is still unknown, although there is increasing evidence to support a neurobiological mechanism. Several factors have been identified that may trigger SMD, which include the following:
- Social Isolation: If the infant is deprived of social interaction and grows alone from an early age, this can result in stereotypic movements in the child.
- Sensory Deprivation: If a child is deprived of sensory inputs in such cases as blindness or deafness, then he/she can develop SMD.
- Environmental Stress: Stressful condition within the family or outside, such as at school can precipitate SMD.
- Heredity: It has been indicated that children who have a family history of SMD, are more susceptible to developing the condition. Therefore, it has been suggested that in certain patients, a genetic component may be present that could trigger stereotypic movements.
- Psychiatric Disorders: Conditions such as obsessive-compulsive disorder (OCD), autism spectrum disorder (ASD), or anxiety disorder can cause SMD.
- Medications: Certain types of stimulant drugs such as cocaine and amphetamines can overstimulate the nervous system, thereby precipitating SMD. Long-term stimulation can appreciably prolong the symptoms. However, the symptoms usually resolve upon withdrawal of the drug.
A person suffering from SMD can be distinguished from a normal person by the following symptoms and signs:
- Hand shaking / waving / wringing / flapping
- Head banging
- Skin picking
- Body rocking
- Head nodding
- Thumb sucking
- Face slapping
- Mouthing of objects
- Nail biting
- Hair pulling (trichotillomania)
- Teeth grinding (bruxism)
- Abnormal running / skipping
Diagnosis can usually be made by taking a detailed medical history, followed by a thorough physical examination. However, since there are several disorders that exhibit similar symptoms, these must be included within the differential diagnosis. Tests, including neuroimaging studies, are usually carried out to eliminate these disorders from the differential diagnosis. Some of these disorders include the following:
Treatment will depend on several factors like the cause(s) of the disorder, symptoms and signs, and the age of the patient. As a rule of thumb, early diagnosis and treatment can lead to better outcomes. Some of the treatment strategies include the following:
- Medications: Antidepressants such as fluoxetine, fluvoxamine, sertraline, haloperidol, chlorpromazine and clomipramine have been found to be beneficial in treating children with SMD. There are also some atypical antipsychotics such as risperidone and aripiprazole that have shown to benefit children with SMD.
- Environmental Modification: The immediate environment (living room / play area) of the child must be modified in such a way so as to ensure complete safety for the child so that the child does not get hurt, which can result in bodily injury. In severe cases, physical restraints may need to be used, such as wearing a helmet to prevent head banging.
- Psychotherapy & Behavioral Training: Proper psychotherapy and behavioral and/or habit reversal training can be very beneficial for the affected child. One such behavioral modification strategy is known as Differential Reinforcement of Other Behaviors (DRO), where the socially acceptable behaviors are reinforced by giving appropriate rewards to the child. Another type of reward technique for altering habits is called Functional Communication Training (FCT), where children are taught to replace undesired behaviors with verbal communication. For example a child can be trained to say “Excuse me” instead of flapping the hand.
Children having the following conditions are at a greater risk of developing SMD:
- Intellectual disability
- Head injury
- Neurological disorders
- Mental retardation
- Family history of SMD
The major complications of stereotypic movements exhibited by children with SMD is that they can severely impair day-to-day activities as well as hamper normal social functioning.
- Stereotypic Movement Disorder - Medline Plus, U.S. National Library of Medicine, National Institutes of Health, USA - (https://medlineplus.gov/ency/article/001548.htm)
- Primary (Non-Autistic) Motor Stereotypies - Johns Hopkins Medicine - (https://www.hopkinsmedicine.org/neurology_neurosurgery/centers_clinics/pediatric-neurology/conditions/motor-stereotypies/)