People perform many repetitive movements throughout the day. People might bite their nails if stressed or nervous.
Someone might pace back and forth if he is anxious or deep in thought, and a bored student in class might tap a pencil against the desk repetitively.
There is an important distinction between repetitive movements that might be associated with a disease and those that are just minor habits.
Many developmental disorders, such as autism and mental retardation, are associated with stereotypical movements. This means that a person has involuntary and repetitive movements that follow a certain pattern.
Excessive head-nodding and arm-waving are considered motor stereotypes, which are usually quite prevalent in these disorders.
However, three neurologists from Hopkins Hospital, led by Harvey Singer, are studying these stereotypical motor behaviors in children without severe developmental disorders.
Prior research has focused more on stereotyped behaviors in children with autistic disorders rather than on non-autistic children. In fact, the largest study previously performed on motor behaviors of non-autistic children only included 40 children.
This new study extended the research conducted on the 40 original patients but also added another 60 patients.
Children could be included in this study if they did not exhibit other psychological or behavioral deficits. Also, these children needed to display repetitive, stereotypical movements.
Rather than minor behaviors like nail-biting, motor behaviors needed to be involuntary and persistent in order to be included in the study. Specifically, excessive hand- or arm-waving and head-nodding were the two main stereotypical behaviors studied.
It is interesting that many of the patients had relatives with similar motor behaviors. The researchers hypothesized that a family history of a stereotypical movement could be one of the causes of this behavior in children.
Other potential causes include the coincidence of stereotypical movements with other disorders, which were not considered major developmental ones.
For example, about half of the children in this study had attention-deficit hyperactivity disorder (ADHD), obsessive-compulsive disorder or other motor tics.
Also, there is the possibility that the brain areas involved in producing Tourette syndrome, which involves involuntary motor and verbal behaviors, could also produce stereotypical motor behaviors in non-autistic children.
These stereotypical movements can occur when a child is experiencing many different emotions simultaneously. Stress, excitement and high attention level can all stimulate these movements.
There is evidence that if the child is distracted or if a parent calls his or her name, the movements can cease temporarily.
Parents were originally told in the past that such movement behaviors would decrease with age. However, this study found that most of these behaviors persisted over the course of the study.
Only six of the 100 children actually stopped exhibiting these repetitive movements. Also, there seems to be better recovery in children who had repetitive head nodding as compared to those with excessive hand waving.
If the symptoms last for more than one year, it seems complete recovery is unlikely.
Further research into the brain circuitry as well as the genetic components to stereotypical motor behaviors could provide a better understanding of how these movements are associated with specific developmental or neurological disorders as well as why they persist in children with typical development.
