What is microcephaly?

Microcephaly is a condition that is present at birth in which the baby's head is much smaller than normal for an infant of that age and gender. Micro means small and cephaly refers to the head. Most children with microcephaly also have a small brain and intellectual disability. However, some children with small heads have normal intelligence.

What causes microcephaly?

Microcephaly is either caused by exposure to harmful substances during the fetal development, or it may be associated with genetic problems or syndromes that may have a tendency to run in families.

Theories suggest that the following may predispose a fetus to problems that affect the normal development of the head during pregnancy:

  • Genetic disorders

  • Exposure to hazardous chemicals or substances

  • Methylmercury poisoning

  • Lack of proper vitamins and nutrients in the diet

  • Intrauterine infection with cytomegalovirus, rubella, or varicella virus

  • Prescription or illegal drug and alcohol consumption

  • Untreated phenylketonuria

Microcephaly can occur alone or in association with other health problems. Acquired microcephaly may occur after birth because of various brain injuries, such as lack of oxygen or infection. A number of genetic disorders also can cause microcephaly. Genes determine out traits, such as eye color and blood type, and can also cause disease. Inheriting an abnormal gene sometimes causes microcephaly.

Autosomal recessive and autosomal dominant are two patterns in which genes can be inherited in a family.  Autosomal means that both males and females are equally affected. Recessive means that two copies of the gene, one inherited from each parent, are necessary to have the condition (in this case, microcephaly). After parents have had one child with autosomal recessive microcephaly, there is a 25% chance, or one in four chance, with each pregnancy, to have another child with microcephaly. Some genetic disorders that cause microcephaly are inherited in an X-linked fashion. While mothers are unaffected, there is a 50% chance that a male child will have the disorder. Female children have a 50% chance of inheriting the gene and the same risk of passing the disorder along to their children.

What are the symptoms of microcephaly?

Microcephaly strictly means a small head, and there are cases where microencephalic individuals have no other symptoms. But the following are the most common features that are seen along with microcephaly. Each child may experience a wide spectrum of symptoms.

  • Appearance of the baby's head is very small

  • High-pitched cry

  • Poor feeding

  • Seizures

  • Increased movement of the arms and legs (spasticity)

  • Developmental delays

  • Intellectual disability

The symptoms of microcephaly may resemble other conditions or medical problems. Always consult your child's doctor for a diagnosis.

How is microcephaly diagnosed?

Microcephaly may be diagnosed before birth by prenatal ultrasound, a diagnostic imaging technique that uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs. Ultrasounds are used to view internal organs as they function, and to assess blood flow through various vessels.

In many cases, microcephaly may not be evident by ultrasound until the third trimester and, therefore, may not be seen on ultrasounds performed earlier in pregnancy. The diagnosis of microcephaly may be made at birth or later in infancy. The baby's head circumference is much smaller than normal. During the physical exam, the doctor obtains a complete prenatal and birth history of the child. In older babies and children, the doctor may also ask if there is a family history of microcephaly or other medical problems. Sometimes the child is born with a normal head circumference but then acquires microcephaly because of a serious condition, such as certain genetic disorders, stroke, traumatic injury, or poisoning. The doctor will also ask about developmental milestones since microcephaly can be associated with other problems, such as intellectual disability. Developmental delays may require further medical follow-up for underlying problems.

A measurement of the circumference of the child's head is taken and compared to a scale that can identify normal and abnormal ranges.

Diagnostic tests that may be performed to confirm the diagnosis of microcephaly and identify abnormalities in the brain include:

  • Head circumference. This measurement is compared with a scale for normal growth and size.

  • Computed tomography scan (also called a CT or a CAT scan). A CT scan uses ionizing radiation (also known as X-rays) to generate 3-dimensional images of the body. Simple skull X-rays are rarely used in the evaluation of childhood brain disorders. CT is a diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce horizontal, or axial, images (often called slices) of the body. A CT scan shows detailed images of any part of the body, including bones, muscles, fat, and organs. CT scans are more detailed than general X-rays.

  • Magnetic resonance imaging (MRI). A diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.

  • Blood tests

  • Urine tests

  • Genetic tests

Lifelong considerations for a child with microcephaly

There is no treatment for microcephaly that will return the baby's head to a normal size or shape. Since microcephaly is a lifelong condition that is not correctable, management includes focusing on preventing or minimizing deformities and maximizing the child's capabilities at home and in the community. For those children that have associated symptoms, positive reinforcement will encourage the child to strengthen his or her self-esteem and promote as much independence as possible.

The full extent of the problem is usually not completely understood immediately after birth, but may be revealed as the child grows and develops.

Children born with microcephaly require frequent examinations and diagnostic testing by their doctor to monitor the development of the head, as well as motor, social, intellectual, and language function, as the child grows. The medical team works hard with the child's family to provide education and guidance to improve the health and well-being of the child. Children with associated disabilities should be referred to the appropriate therapists for evaluation and intervention.

Genetic counseling may be recommended by the doctor to provide information on the recurrence risks for the disorder and any available testing.