May 12 (HealthDay News) -- Only about 5 percent of people with multiple sclerosis are diagnosed when they're children, but like adults with MS, the disease can affect cognitive function, causing memory and attention problems, and possibly low IQ scores.

And, the younger a child is at the time of diagnosis, the more likely he or she is to have a low IQ, according to new research published in the May 13 issue of the journal Neurology.

"In childhood cases, the impact of the disease on cognitive functioning may be more dramatic than that observed in adults," said study author Dr. Maria Pia Amato, an associate professor of neurology at the University of Florence, in Italy.

Multiple sclerosis is a disease of the central nervous system. The disease leads to the destruction of myelin -- a protective coating found on nerve cells. Without their myelin coating, the nerve cells can't efficiently send signals between the brain and other parts of the body. Within the brain, this can slow or stop nerve impulses, according to Nicholas LaRocca, vice president of health care delivery and policy research at the National Multiple Sclerosis Society (NMSS). Additionally, he said, MS can cause a gap in nerve fibers, and, in some cases, can actually cause brain tissue to shrink.

"The overall organization of the brain is being impaired," he said.

LaRocca's colleague, Rosalind Kalb, vice president of the professional resource center at NMSS, said most people describe the effects of the disorder as feeling as if their brain "has slowed way down."

"What that means for a child in a school situation is that if the incoming information is coming in faster than that person can process it, they won't remember it later, because they didn't get to process it effectively to begin with. So, they don't learn what they need to learn," said Kalb, who along with LaRocca wrote the book, Multiple Sclerosis: Understanding the Cognitive Challenge.

An estimated 250,000 to 350,000 Americans are believed to have multiple sclerosis, according to the U.S. National Institute of Neurological Disorders and Stroke. The course of the disease is highly unpredictable, with some people experiencing only mild symptoms, while others are disabled by it. Many people also have periods of remission, when they have no symptoms.

And, that same variability holds true for cognitive symptoms. "These kids aren't developmentally disabled. Some will experience problems, and some won't. They have to learn to use their strengths to compensate for the pockets of problems that can affect their learning," Kalb said.

Amato's study included 63 children with MS and 57 healthy "controls." They ranged in age from 8 to nearly 18, with an average age of 15. Each child completed numerous tests to assess different areas of cognitive function.

Thirty-one percent of the children with MS were deemed to have a cognitive impairment, which meant they failed at least three of the tests.

"Five patients (8 percent) exhibited a particularly low IQ, less than 70, and we found that a lower IQ was significantly associated with a younger age at onset. Only one case had an MS onset after 13 years of age, whereas in the remaining four children, MS started before 13 years of age," Amato said.

Additionally, she said, "MS negatively affected school and everyday activities in 56 percent of the subjects."

LaRocca said the findings are similar to what has been seen in adults, and what this study really does is "call attention to the fact that these youngsters need special attention and support. You'll find some functions affected, some severely, some mildly and some not at all, and you'll find certain strengths you can work with." For example, "if verbal memory is affected, but visual memory isn't, use more visual cues in teaching," he advised.

Amato added: "In general, treatment and support may help the [child] and the family to cope with psychosocial difficulties. Moreover, it is possible that brain plasticity, as well as reparative and compensatory abilities, may be more efficient in this age range. Therefore, early treatment strategies, both rehabilitative and pharmacological, may lead to a better outcome."

The study was funded, in part, by a grant from drug maker Biogen-Dompe, which produces medications for MS.

SOURCES: Maria Pia Amato, M.D., associate professor, neurology, University of Florence, Italy; Rosalind Kalb, Ph.D., vice president, professional resource center, National Multiple Sclerosis Society, New York City, and co-author, Multiple Sclerosis: Understanding the Cognitive Challenge; Nicholas LaRocca, Ph.D., vice president, health care delivery and policy research, National Multiple Sclerosis Society, New York City, and co-author, Multiple Sclerosis: Understanding the Cognitive Challenge; May 13, 2008, Neurology