May 12, 2008 -- Multiple sclerosis (MS) that strikes during childhood may disrupt a key phase of brain development and appears to have a profound negative impact on a child's ability to think and pay attention.
Scientists reporting in the May 12 issue of Neurology say that the earlier MS develops, the more likely a child will have a lower IQ score.
MS is a central nervous system disease that attacks myelin, the material that covers and protects nerve fibers. The damage gets worse over time and leads to symptoms such as numbness, tingling, fatigue, loss of vision, and in severe cases, paralysis.
It most commonly develops in adults after age 20. However, pediatric MS affects about 8,000-10,000 people under age 18 in the U.S., according to the National Multiple Sclerosis Society.
Researchers theorize that pediatric MS strikes at a time when the part of the brain involved in cognition is maturing. Previous uncontrolled studies have shown a link between cognitive impairment and MS. However, information about the neuropsychological effects of MS in children and teenagers has been limited.
"It's possible that MS can show an even more dramatic effect on the thinking skills and intelligence in children than in adults, since the disease might affect the brain at a time when it is still developing," researcher Maria Pia Amato, MD, of the University of Florence in Italy, states in a news release.
Amato gave an array of intelligence tests to 63 children with MS and compared their scores to 57 healthy children of similar ages. The tests were designed to measure overall intelligence, memory, language ability, and other thinking skills.
The tests showed that the children with MS were more likely to have low intelligence scores and problems with memory, attention, and other thinking skills. Thirty-one percent of the children with MS met the criteria for significant cognitive impairment, meaning they failed at least three of the tests. Fifty-three percent of the children with MS failed at least two of the tests.
Amato's team noted language difficulties in about 30% of the children with MS. Language problems are uncommon in adults with the disease.
"Since the disease occurs during a critical phase for language development, children may be particularly vulnerable to language problems," Amato states. "Even subtle language difficulties are likely to have important functional consequences. Therefore ... assessment of language function in pediatric MS deserves particular attention in future studies," she writes in the journal article.