Hesperian Health Guides
Causes of Cognitive Delay
 typical head size
smaller than usual head size
(microcephaly) |
| A child with microcephaly (small head) has cognitive delay and often also develops vision, hearing, or other physical problems. See measurements of head size. |
There are many causes.
- Often the cause is not known.
- Some children are born with a very small brain, or the brain does not grow or work in the usual way.
- Sometimes there is a change in the chromosomes or the tiny chemical messages that determine what a child will be like. This is what happens in Down syndrome.
- Sometimes a mother did not get enough of a certain food or mineral during pregnancy (see “Hypothyroidism”).
- Brain injury can happen either before, during, or after birth. In addition to having cognitive delay, these children may also have cerebral palsy, vision loss, hearing loss, or seizures. Common causes of cognitive delay from brain injury are discussed in Chapter 9, and include:
- a mother had German measles during early pregnancy.
- meningitis (brain infection) from bacteria, tuberculosis, or malaria, most often during early childhood.
- hydrocephalus, often with spina bifida.
- Other causes such as head injury, brain tumor, poisoning from lead, pesticides, infection from the mosquito-carried Zika virus, untreated HIV infection, certain medicines and food, and some forms of muscular dystrophy or atrophy.
In many parts of the world, the most common causes of cognitive delay are brain injury and Down syndrome. But in some mountainous areas, it is very often caused by lack of iodine in food and water.
Usually there is no treatment for cognitive delay. Therefore, we often do not need to know the exact cause. Instead, we need to help the child develop the best he can. However, in some cases, certain medicines, changes in diet, or prevention of further poisoning can make a big difference. If a child has any signs of hypothyroidism or seems to be gradually losing mental ability, try to get expert medical advice.
Prevention of cognitive delay is discussed with its different causes. See especially cerebral palsy, Down syndrome, and hypothyroidism.