They may be hyperactive, head bang or rock, or bite or pick their skin. Some develop obsessions with certain objects. Many have a fascination for hair and can't resist pulling it. Drooling is a common problem, some children grow out of it, but if they don't there is a very successful operation to control it. It is very difficult to predict how a particular child will develop, it doesn't seem to be related to the amount of genetic material which is lost.
All parents can do is wait and see.
Early and ongoing intervention is necessary from Speech Therapists, Physiotherapists and Occupational Therapists. It depends where you live what else you can get, but there are special nurseries, or home intervention programmes in most areas. Children with CDC will probably need a lot of equipment, depending on their age. For some children drugs have been used with success to control behavioural or sleep problems. The vast majority of children will attend a special school, though a few will cope in mainstream with support.