Preemies' Brains Stay Small in Grade School

Study finds differences up to age 8, especially in boys

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HealthDay Reporter

MONDAY, Aug. 9, 2004 (HealthDayNews) -- Certain brain areas of children who are born prematurely appear to be smaller than normal and remain that way even by the time they're in the third grade.

The differences concerned the areas of the cerebral cortex responsible for reading, language, emotion and behavior. They were more pronounced in boys than in girls, says a study appearing in the August issue of the Journal of Pediatrics.

"There are some long-term anatomical structural ramifications of very preterm birth, meaning that the complications are not just limited to the period immediately after birth," said study author Dr. Allan Reiss, a professor of psychiatry and behavioral sciences at Stanford School of Medicine and director of the Stanford Psychiatry Neuroimaging Laboratory. "Issues related to how the brain develops and how the brain functions are probably still active, or at least potentially relevant, even up to age 8."

But Dr. Pradeep Mally, attending neonatologist at New York University School of Medicine, cautions against applying the findings to all preemies. "I'd be very skeptical to generalize those statements because each baby is different," he said.

According to the article, 30 percent to 50 percent of very low birth weight preterm babies have neurodevelopmental problems during their preschool years, 50 percent need special help in grade school, and 10 percent will be diagnosed with cerebral palsy. Preterm boys seem to be especially vulnerable to these complications.

Some magnetic resonance imaging (MRI) studies have suggested that preterm infants may have different white matter volume and structure in the brain. White matter consists mainly of the tracks and pathways that enable communication between different parts of the brain, while gray matter consists of cell bodies and synapses, where signal processing happens.

To try to further elucidate the brain mechanisms behind these difficulties, Reiss and his colleagues did MRIs on 65 children, all 8 years old, who had been born preterm and compared them to the MRIs of 31 kids the same age who had been born full term. The preterm babies were born at about 28 weeks and weighed only two pounds at birth.

Overall, both gray matter and white matter volumes were smaller in the preterm group. Only preterm males, however, had significantly reduced white matter.

"The differences in the white matter were pretty prominent," Reiss said. "We see a pretty big shift in the volumes of certain brain structures in individuals who are preterm, but particularly in males when it comes to white matter."

Hormones or genetics -- or both -- may be responsible for the gender differences. "In general, men are more at risk for a lot of different learning and behavior problems," Reiss pointed out. "It probably has to do with the fact that females have two X chromosomes that give them some backup. There is some redundancy that males don't have."

Reiss hopes that one day this work may contribute to the development of treatments to protect the brains of preemies, but no immediate result is expected.

"There are things we can do for learning disabled children regardless of the cause," Reiss said. "Treatments don't change."

Parents of preemies may also want to pay closer attention to possible language and learning difficulties, particularly in boys. "The earlier you address the issue, the more chance you have for not having significant problems later on," Reiss said.

More information

For more on premature babies, visit the Nemours Foundation.

SOURCES: Allan Reiss, M.D., professor, psychiatry and behavioral sciences, Stanford School of Medicine, director, Stanford Psychiatry Neuroimaging Laboratory, and co-director, Center for Brain and Behavior, Lucile Packard Children's Hospital, Palo Alto, Calif.; Pradeep Mally, M.D., attending neonatologist, New York University School of Medicine, New York City; August 2004 Journal of Pediatrics

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