Reports of increasing numbers of children born with microcephaly in some regions of the world most affected by the mosquito-borne Zika virus are mounting. What is this condition?
What is microcephaly?
Microcephaly is a rare neurological disorder in which a child’s brain does not fully develop, resulting in an abnormally small head size. Its severity varies. The disorder can be present at birth or acquired in the first years of life. The disorder is generally associated with varying degrees of intellectual disability (mental retardation), although a small percentage of children will experience no developmental delays. Additional problems among affected children could include delayed speech and motor functions, vision and hearing deficiencies, dwarfism or short stature and/or other problems associated with brain abnormalities.
What causes microcephaly?
Microcephaly occurs most often when the brain fails to grow at a normal rate; the skull’s growth is determined by the brain’s size. A variety of conditions or exposures can cause the disorder, including exposure to harmful substances and possibly viruses during fetal development. Some cases may be genetic. Causes include:
• Maternal prenatal infections, including rubella (German measles)
• Chromosomal disorders (such as Down syndrome)
• Craniosynostosis, a birth defect characterized by the premature closure of one or more of the fibrous joints between the bones of the skull (called the cranial sutures) before brain growth is complete.
• Bacterial meningitis
• A mother’s use of drugs or alcohol during pregnancy
• Exposure to chemicals or radiation
• Metabolic of biochemical disorders such as phenylketonuria (PKU)
How is it diagnosed?
Microcephaly can sometimes be diagnosed by prenatal ultrasound, although the condition might not be evident until the third trimester of pregnancy. The diagnosis is usually made after birth by measuring the child’s head circumference. Additional information about the cause of the microcephaly will likely entail a brain MRI scan and perhaps metabolic and genetic tests
Treatment for microcephaly
Except for surgery for craniosynostosis, there is no treatment that can reverse the disorder. Intervention programs with occupational, physical and speech therapists can help affected children have an enhanced quality of life. Physicians might recommend medication for some complications of microcephaly, such as hyperactivity and seizures.
Prevention
Because some cases of the disorder are genetic, genetic counselors can help you determine the risk of microcephaly in future pregnancies.
In general, always follow your physician's advice to avoid behaviors or exposures that could put you at greater risk before and during pregnancy.
Care at Johns Hopkins
At Johns Hopkins Children’s Center, children with microcephaly are often cared for by providers in the Division of Pediatric Neurology, or occasionally (if the situation warrants) by pediatric neurosurgery or genetics. Many of these children are followed in the neighboring Kennedy Krieger Institute.
Reviewed by Carl Stafstrom, M.D., Ph.D., director, pediatric neurology at Johns Hopkins, Johns Hopkins Children's Center.