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  Home> Publications > QUEST >Vol 4 No 1 January 1997
THE BRAIN IN DUCHENNE DYSTROPHY [DMD]
Are Learning Disabilities Part of the Picture?
by Margaret Wahl

Kindergarten was a rough year for Wyatt Moore of Rochester, N.Y. Wyatt has Duchenne muscular dystrophy, but the muscle problems hadn't had much impact yet. Instead, there were other things troubling Wyatt and his mother, Vicki.

"It seemed like it was a processing problem," Vicki Moore says of her son's difficulties. "He didn't talk until he was 3H, and he didn't seem to understand words that were said to him. He had a real hard time in school."

Things were rough for Wyatt even in preschool, but kindergarten, says Moore, "was a disaster." There were 15 children in the class, and Wyatt "just could not deal with it." He made strange clucking noises, developed a habit of hiding underneath tables and couldn't seem to talk about anything.

"You would talk to him about something, and he would just talk about something else," his mother says.

His social skills were nonexistent. "Instead of playing a game or talking with someone, he'd go and grab him and they'd both fall down. He didn't realize people could get hurt that way. Just not being able to figure out what's going on would be the best way to describe it," Moore says.

Often by mid-morning, the school would call and ask Moore to pick up her son. "They couldn't deal with him anymore, and he couldn't deal with being there," she says.

In nearby Webster, N.Y., 16-year-old Wesley Rehse and his parents, Diane and Dirk, can recall having had some of the same frustrations. Wesley also has Duchenne dystrophy, and has had cognitive (related to thinking) difficulties since preschool, long before his muscle weakness became severe.

"In preschool, he couldn't learn his phone number and address," Diane Rehse says.

In elementary school, he could manipulate mechanical things, do puzzles and cut with a scissors, but, when it came to writing, his hands didn't seem to work. And, while he could do math, he couldn't seem to learn to read.

Joseph Cohan also has Duchenne. He's 9 now and lives in Stratham, N.H., a small town near Portsmouth. His mother, Margaret Cohan, didn't think much about academic difficulties when Joe started kindergarten. She and her husband, Dennis, were thinking more about mobility problems in the future and were building an accessible home. Joseph hadn't encountered any major problems in preschool.

Kindergarten was a different story. He didn't seem to be learning as fast as the other children. By first grade, Margaret Cohan says, it became obvious that he had some learning disabilities. There were difficulties with his short-term memory, she says, as well as problems processing information he heard.

"He had trouble with sequential directions," Cohan says. "If you told him three things, by the time you got to the third thing, he'd forgotten the first."

There were problems in fine motor coordination (use of the hands), and difficulty with attention. "He's highly distractible," his mother says, "but he's not hyperactive, just inattentive. He'll sit there and look around unless there's someone to keep him on task."


THE IQ SCORE DEBATE

Learning problems, sometimes severe enough to be termed mental retardation, have been noticed in Duchenne muscular dystrophy ever since Duchenne himself first described the disease more than 100 years ago.

In the 1960s and '70s, there were a rash of studies to try to determine whether children with Duchenne had lower IQ scores than other children and, if so, whether the lower scores were part of the disease itself or whether they were a result of educational deprivation, emotional distress at having a progressive disease with a poor prognosis or environmental factors.

Almost all these studies used standard IQ tests, such as the Stanford-Binet Intelligence Scale or the Wechsler Intelligence Scale for Children. They usually found that the average IQ of the Duchenne children was in the 80s, compared with an average IQ for children in general of 100. IQs in the 80s are considered normal intelligence scores, but below average. IQs in the 70s are considered borderline between average and mentally retarded. Only some of the Duchenne children had IQs in the mentally retarded range, and many had very high IQs. The researchers were baffled.

Many suggested that the disease itself might have an effect on the brain, but they didn't know what that effect might be, and they couldn't understand why it was so variable among children with a similar degree of muscle disease. One early theory was that a toxic product of muscle degeneration might be poisoning the child's developing brain, but this theory couldn't account for the marked variation among children.

Some doctors said that there was no real lowering of IQ in Duchenne, and that the lower IQ scores only reflected emotional distress in the child and his family, disrupted education, impaired mobility and fewer life experiences, or perhaps a subtly transmitted attitude on the part of parents and teachers that learning isn't important for a boy with Duchenne, since he probably won't live to have a career.

An important clue emerged when studies directly compared children with Duchenne to children with spinal muscular atrophy. These studies found that the children with SMA had normal IQs, while the children with Duchenne, despite having a similar degree of physical disability and similar circumstances, had lower than average IQs. Clearly, something more than social impact was causing the cognitive problems in Duchenne.


THE GENE AND THE BRAIN

In 1986, the gene for a protein later named dystrophin was identified by MDA researchers and found to be the key to Duchenne. Soon after, the same gene was implicated as the cause of Becker muscular dystrophy, a less severe form of the disease.

Genes are recipes for proteins and, when a recipe is wrong, the protein made from it is made wrong. In the muscle cells of boys with Duchenne, the dystrophin protein isn't made at all, or is made so poorly that it's useless to the cell and quickly disintegrates. In boys with Becker, the protein is flawed, but still provides some structural support in the muscle cell.

diagram of brain, showing cortex, hippocampus, cerebellum
Dystrophin is normally found in the brain's cortex, cerebellum and hippocampus -- as well as in muscle. A new theory says it may be lacking in the brains of boys with Duchenne dystrophy, just as it's missing in their muscle cells, and that this could explain the learning disabilities that often accompany the muscle disease.
By the early 1990s, researchers began to see more than they had expected. The dystrophin gene wasn't just a muscle protein gene. There was also a brain form of dystrophin, made from the same gene, but in a slightly different way.

Not surprisingly, scientists began to speculate that, if this brain protein were also flawed in Duchenne, it might account for the cognitive problems seen in the disease. And, if different people had different flaws in the same gene, it might account for some of the variation seen with these problems.

This theory, with some modifications, is what most doctors and scientists believe today, though few would deny that social and emotional factors also play a role in intelligence and behavior.


RETARDATION IS RARE

"The vast majority of patients with Duchenne are not mentally retarded," says Dr. Mark Mehler, a professor of neurology and neuroscience at Albert Einstein College of Medicine in New York.

Instead, he says, they may have subtle and complex cognitive and behavioral deficits, or learning disabilities, which can be accounted for by dystrophin abnormalities. Mehler, an MDA grantee, is a neurologist who practices medicine and studies the brain.

Much of Mehler's research is based on what is now known about the dystrophin gene, work done by MDA-sponsored molecular geneticists Louis Kunkel at Boston Children's Hospital, Jeffrey Chamberlain at the University of Michigan, and Uri Nudel at the Weizmann Institute of Science in Rehovot, Israel.

The dystrophin gene is the largest gene ever found, and is among the most complex. It has at least eight start sites, known as promoters, meaning there are eight places in the gene where the recipe for a protein can begin. So far, four of these start sites have been found to begin recipes for brain forms of dystrophin -- for two long and two short forms of the protein. Only one site has been found that starts the muscle dystrophin recipe.

A lot of the variation in cognitive functioning in children with Duchenne, Mehler says, can be explained by the differing locations of their mutations (abnormalities) in the dystrophin gene. Some children probably make some of the brain forms of dystrophin, while others may not make any, or may make some imperfectly. Mehler believes few children make the two long forms of brain dystrophin, because these two forms are almost the same as the muscle form, and a genetic mutation that affects the muscle protein recipe would very likely also affect these brain forms.

Children and adults with Becker haven't been well studied with regard to cognitive functioning, but Mehler suspects that, because of their dystrophin abnormalities, they too probably have more learning disabilities than the general population.


FLAWED INTERACTIONS

"The vast majority of children with Duchenne don't have classical intellectual deterioration," Mehler says. "What they have is an inability to communicate what they know and to interact effectively with the outside world."

Mehler says they can't communicate what they know because of flaws in the way they receive information and retrieve it from their brain's storage areas.

Standard IQ tests rely heavily on input-output functions when they attempt to measure "intelligence." If, for example, a child is so distracted by a fly in the room that he can't pay attention to the test, his score will be significantly lower on a standard IQ evaluation.

Inability to focus is common to almost all the Duchenne patients Mehler has tested, and he thinks it's responsible for a lot of misunderstanding about IQ.

"I can guarantee you that most of the IQ difference in Duchenne is due to the attentional problem and not due to intrinsic problems in intellectual attainment," Mehler says.

He has found that children with Duchenne have problems in three main areas, all of them hampering their interactions with the world and its information: attention focusing, verbal learning and memory, and, to a lesser extent, emotional interaction.


A DUCHENNE PROFILE?

Among the questions researchers have set out to answer is whether there are cognitive and behavioral abnormalities common to many Duchenne patients, even if they differ in severity. If there are, doctors would call that a "Duchenne profile," and its existence would certainly point to biological causes closely associated with this disorder.

Mehler believes that, so far, the evidence points to a Duchenne profile of brain-associated deficits.

The first, and most common, is an attention deficit disorder, although Mehler cautions that this term is both overused and misused today. Children with attentional difficulties don't just have trouble focusing attention; they also have trouble letting go of attention.

"We'll have Duchenne kids that will focus on an object like it's a holy totem, and then two seconds later, they're doing seven other things that they'll attend to for three seconds and be gone," he says. "They can't modulate [regulate] their attention."

Another misunderstanding is confusion of attention deficit with hyperactivity. In young children, he says, attention deficits show up as hyperactivity; but, as they get older, they change to inattention without hyperactivity, even in children without muscle disease.

The second area of difficulty is more subtle and harder to explain, but it underlies several of the learning and language disabilities often seen with Duchenne. The problem, Mehler says, is with a brain process known as the "phonological code."

The phonological code is a system the brain uses to break down language into its smallest units of sound (known as "phonemes"). Normally, when people hear or read words, the brain processes and stores the words in a code of "sound bites," or phonemes, and probably later retrieves them the same way, before recoding them back into words.

If the phonological code isn't working properly, processing spoken language becomes very difficult, and what hasn't been processed correctly in the first place becomes difficult or impossible to retrieve, or remember. If the phonological code is essential for reading, and there are defects in one's phonological code, then learning to read and remembering what has been read also become daunting tasks.

Fortunately, as with most learning disabilities, deficits in the phonological code can be gotten around, at least to some extent, with special education that helps children use pathways other than phonology for learning, memory and language processing.

The third area in which Duchenne patients have shown abnormalities is perhaps the least clear, and the most controversial. At least some boys have difficulty with emotional interaction that suggests a lack of "connectedness," making a child appear immature or "off" in some way that's hard to define.

The three parts of the brain in which the most dystrophin would normally be found roughly correspond to the functional areas where Duchenne children tend to have difficulties, Mehler says. It's found in the cortex, where attention is regulated and signals from the rest of the brain are integrated; the hippocampus, where short-term memories are processed and prepared for storage as long-term memories elsewhere in the brain; and the cerebellum, where complex motor (movement-related) functions, such as walking, playing an instrument or writing, are learned and fine-tuned.

According to Mehler, recent evidence suggests the cerebellum may also be involved in other kinds of information processing and perhaps in social connectedness.


GETTING AROUND THE DEFICITS

Telling parents that their child's cognitive differences may be due to a brain abnormality isn't meant to be frightening, but to encourage and help parents to get the kinds of intervention needed for their children, Mehler says.

He recommends an evaluation by a developmental or pediatric neuropsychologist as soon as a child receives a diagnosis of Duchenne, so that educational and psychological interventions can begin right away. (Many parents have found the psychologists and educators in their own school systems to be very effective, and most MDA clinics are located at major medical centers that can make referrals to a neuropsychologist if a parent requests one.)

Often, Mehler says, parents of children with Duchenne feel that they are helpless, passive partners in their child's care and development. But parents can make a difference by following exercises and ways of interacting with the child prescribed by a neuropsychologist. Such prescriptions should begin as soon after diagnosis as possible, Mehler says.


SPECIAL EDUCATION

Wyatt Moore, Wesley Rehse and Joseph Cohan are in special education now, and all have made progress. The precise solutions differ for each, but there are some common threads.

Wyatt, now 7, has moved from his regular public school to a public school for students with special needs, part of the New York state BOCES (Board of Cooperative Educational Services) program. Instead of a class of 15 children, he's now in a class of five, and, his mother says, "is doing wonderfully."

Click here to read more about Joseph Cohan's IEP - Individualized Education Program.

Like all children in special education, Wyatt has an Individualized Education Program (or Plan), which sets specific educational objectives for a child, the means to reach them and the methods for evaluating whether they've been reached. (See "Joseph's IEP.")

He's beginning to put things together in reading, his mother says, using a visual processing method specified in his IEP. He still has great difficulty writing, which may be due to poor hand-eye coordination or to weakness in his hands. It took him a year to learn to write his name, but now he can do it.

Wyatt is also developing some social skills, his mother says. "Before, he just could not figure out what to do," she says. Vicki Moore isn't sure Wyatt can yet interpret other people's feelings, but she says he's doing better and treats animals, such as his grandfather's cats, with more understanding.

Reports from school now say "good" and "excellent," while last year they were coming back with comments like "poor" and "fair." And, he doesn't dread going to school anymore.

When Wesley Rehse started first grade 10 years ago, he, like Wyatt Moore, was placed in a BOCES program in a special school. But his mother doesn't think it was the best situation for him, because the other children were mostly from very troubled families. In fourth grade, he switched to a special education class in a regular public school, where, she says, "he flowered."

Wesley also has an IEP. He physically can't write and has a classroom aide do some of the writing for him. (He can still use his fingers to do art work, including painting Ukrainian Easter eggs.) Math is one of Wesley's stronger subjects, but reading is very hard for him. Learning to read with phonics proved impossible, but, with a sight reading method known as "whole word reading," he's been able to read at about third-grade level. "Books on tape did nothing for him," his mother says, explaining that learning for Wesley has to be visual.

Social life in school is still a problem, Wesley says. He says he's the only child with physical disabilities in his present class, and the other kids don't have the same problems he has. As in his first school, some of his current classmates come from unstable homes, and their attitudes toward school aren't the same as his. Wesley describes himself as "sort of obsessive-compulsive," and he doesn't like it when the less committed students interrupt or distract him.

Wesley enjoys video games and exploring the Internet, but his greatest enjoyment comes from tending his two dogs and eight lizards.

"Tiffany always stays with me," he says of one of his dogs. "I like animals, because they comfort me. I'd like to work at a zoo with lizards, snakes and alligators, and help people understand not to be afraid of them."

"We don't let the disease control us," says his mother, Diane. "We adapt to it. Our quality of life is above average."

Joseph Cohan is receiving special education services and classroom modifications in his regular third-grade class in Stratham, N.H. He started his special education services in first grade, after testing revealed specific learning disabilities, despite an average IQ.

He has a classroom aide 20 hours a week. He can write, but not very well, and is using some assistive technology in this area. He can read at a fourth-grade level, and, unlike many children with Duchenne, reads phonetically, his mother says. Math has been very difficult, and his mother attributes this to his poor memory.

Joseph is still highly distractible, but a swimming class has helped enormously with attention focusing. He also receives physical, occupational and speech therapy, as well as psychological counseling, all through the public school system.

Margaret Cohan is extremely involved in her son's education and has become an advocate for other parents in her school system and at the state level.

Lately she's found that some teachers feel overly sorry for her son because of his prognosis and they worry only about how he feels. A colleague even compared her to the "wicked stepmother" in fairy tales for pushing her son too hard in school. But, Cohan says, "He deserves an education. I want them to push him, not brutalize him."

Mehler wants all children to get the attention they need. "There are ways of helping these children to adapt, to act upon what they know," he says.

"What we need to impart to families is that there's this other area besides the motor disability that they really need to pay attention to. And we're not just talking about doing well in school or being smart. We're talking about maximizing their ability to interact in ways that are constructive for them -- to communicate, to derive a measure of comfort from interacting with other people, to enjoy reading. As we learn more about some of the deficits, we can improve how they function. It's really important to maximize what they can do intellectually and emotionally."

 
     
     
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