What is microcephaly?

Microcephaly is a neurological disorder in which the circumference of the head (the measured distance around the top) is smaller than average for an infant’s size and age. The disorder can be present at birth or acquired during the first few years of a child’s life. Microcephaly is often associated with some degree of mental retardation. However, in 15% of the cases, the child has normal intelligence. Microcephaly is rare, occurring from 1 per 6200 to 8500 births.

What causes microcephaly?

The growth of the skull is determined by the expansion of the brain. Microcephaly occurs most often because the brain fails to grow at a normal rate. This can be caused by a variety of conditions or exposure to harmful substances during fetal development. Some of these causes include:

  • Chromosomal disorders such as Down syndrome, Cri du chat syndrome, Trisomy 13, and Trisomy 18.
  • Maternal viral infections such as rubella (German measles), toxoplasmosis, and cytomegalovirus.
  • Maternal alcoholism or drug abuse.
  • Maternal diabetes.
  • Mercury poisoning.
  • Uncontrolled maternal PKU.
  • Maternal malnutrition.

Acquired microcephaly might occur after birth due to various brain injuries such as lack of oxygen or infection.

What are the symptoms of microcephaly?

Aside from a noticeably smaller head, the following are the most common symptoms of microcephaly:

  • High-pitched cry.
  • Poor feeding.
  • Convulsions.
  • Increased movement of the arms and legs (spasticity).
  • Hyperactivity.
  • Developmental delays.
  • Mental retardation.

As the child grows older, his or her face continues to grow while the skull does not. This causes the child to develop a disproportionately large face, a receding forehead and a loose, often wrinkled scalp. The rest of the body is often underweight and proportionately smaller than normal.

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