Microcephaly on the rise.

Neurology Now
What Is Microcephaly?: Although uncommon in the United States, this neurologic condition is gaining attention, thanks to a new virus. We give you the facts about it.

If “Zika” is a new word in your vocabulary, then chances are so is “microcephaly.” Zika, a mosquito-borne virus, has been linked to microcephaly and other disorders, and concerns about it have led to travel alerts for areas where Zika is present.

But microcephaly, which literally means “small head,” is not new, says Hannah M. Tully, MD, MS, an acting assistant professor in the department of neurology at Seattle Children’s Hospital. “It is a descriptive term that covers a number of distinct conditions, and its consequences can range from minimal to severe neurologic impairment.” State tracking systems of birth defects have estimated that microcephaly ranges from two babies per 10,000 live births to about 12 babies per 10,000 live births in the United States, according to the US Centers for Disease Control and Prevention (CDC).

The defining characteristic is a head statistically smaller in circumference than standard measurements for babies of the same sex and age, which can indicate that the brain hasn’t developed normally or has stopped growing. Microcephaly can be genetic, occurring as a consequence of chromosomal disorders such as Down syndrome or because of small changes within single genes. It can also be caused by infections such as cytomegalovirus, a member of the herpesvirus family; rubella (German measles); or varicella (chicken pox) during pregnancy.

Children with microcephaly may have normal intelligence and their heads may grow bigger, but they will remain behind normal growth curves for head circumference. In other cases, particularly those associated with the Zika virus, children may have complications such as delayed speech, language disorders, poor coordination, seizures, visual impairment, and cognitive deficits. Some children are fully dependent on others for daily living needs.
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The prognosis for microcephaly is often determined by its cause. If the cause is a metabolic disorder, for example, microcephaly may be arrested by immediate treatment, such as medication. [The prevalence of metabolic disorders among children with microcephaly is estimated to be at 1 to 5 percent, according to the 2009 guidelines on assessing microcephaly from the American Academy of Neurology.] Once a baby is diagnosed, the family should be referred to a pediatric neurologist, says Yolanda F. Holler-Managan, MD, FAAN, an assistant professor of pediatrics neurology at the Feinberg School of Medicine at Northwestern University in Chicago.
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During her pregnancy, a sonogram indicated that Leah Wright had contracted cytomegalovirus, which is thought to have caused microcephaly in her daughter Isla Rose. When her baby’s small head was seen on an ultrasound at 24 weeks, Leah’s doctors mentioned microcephaly. A magnetic resonance imaging scan at 27 weeks showed even more damage to the brain.

Isla Rose, now 2, was born with profound hearing loss and cerebral palsy. She also has seizures and her developmental level is that of a 3- to 4-month-old. “But she is a happy little girl,” says Leah, adding that Isla Rose’s life continues to improve. She is about to get a cochlear implant and sees specialists for other interventions, says Leah. “Even though we were scared beyond belief and we didn’t know what to expect, and we still don’t, we truly believe in hope and you have to be positive.”
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The Zika virus was first identified in Uganda and has been found in the Americas only in the last year. Typically, it causes mild, flu-like symptoms, according to the CDC. But in Brazil, cases of congenital microcephaly in babies of mothers who were infected with the virus while pregnant have been reported, and Zika infections have been confirmed in several infants with microcephaly. A team of experts from the CDC is collaborating with Brazilian neurologists and other health officials to determine whether, in fact, Zika and microcephaly are linked.

“I have no doubt in my mind that Zika is capable of causing microcephaly,” says Dr. Tully. But she and Dr. Holler-Managan caution that bias could contribute to a link when there isn’t necessarily one. “Some cases of microcephaly linked to Zika could instead be caused by other viruses or genetic conditions. What hasn’t shaken out yet is how many of these cases Zika caused,” Dr. Tully explains.

Almost all cases in the US have been in people who traveled to countries where the virus is present, including several pregnant women who gave birth to children with microcephaly after traveling to Zika-infected areas.

Health officials expect the virus to appear at some point because several states have the Aedes aegypti mosquito that can spread Zika. In anticipation of the eventual appearance of the virus, the National Institutes of Health has announced available funding to develop new tests to diagnose the virus, vaccines to prevent it, and drugs to treat it.

© 2016 American Academy of Neurology

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