Microcephaly | Symptoms and Causes

What are the signs and symptoms of microcephaly?

The main feature of microcephaly is a head size that is much smaller than normal for the child’s age and gender.

Other signs and symptoms can vary widely from child to child. They can include:

  • poor weight gain and growth
  • poor appetite/feeding
  • difficulty with movement and balance
  • abnormal muscle tone (too loose, too tight)
  • speech delays
  • mild to severe learning disabilities

Some children with microcephaly also have other medical problems such as:

  • very short stature or dwarfism
  • facial deformities
  • seizures
  • vision and hearing problems 
  • joint deformities (for example, in children with Zika infection)

What are the causes of microcephaly?

Microcephaly has a variety of causes. Knowing the cause is important in predicting what symptoms a child with microcephaly will have. For example, some forms of microcephaly are linked with severe developmental delay or a high risk for seizures, while others are not. Some forms can impair motor function or affect other organs in the body. Microcephaly linked to prenatal infections such as Zika sometimes causes with vision and hearing problems.

Microcephaly is often congenital, meaning a baby is born with the condition. In other cases, a baby can develop microcephaly after birth.

Causes of congenital microcephaly include:

  • Prenatal infections: Exposure to the Zika virus, especially in the first trimester of pregnancy, can damage nerve cells in the brain. Other infectious agents can also cause microcephaly, including rubella (German measles), chickenpox, toxoplasma and cytomegalovirus.
  • Genetic mutations: Several hundred genes have been linked with microcephaly, and more are still being discovered. Defects in these genes can interfere with the brain’s growth. In some cases, microcephaly may be related to Down syndrome or certain neurometabolic disorders.
  • Other causes during pregnancy: There is evidence that alcohol and substance abuse, inadequate nutrition, untreated phenylketonuria (PKU) or exposure to toxic chemicals and certain prescription drugs during pregnancy can cause microcephaly in a baby.

Causes of microcephaly during infancy include:

  • genetic mutations
  • traumatic brain injury
  • lack of oxygen to the brain
  • an infection in the brain

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