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Our Findings |
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So what have we learned? Here are some highlights:
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DMD Project at Columbia University |
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Sergievsky Center |
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*** We found that boys with DMD tend to have relatively weak verbal immediate memory skills, regardless of their intellectual level. For some boys, this causes real problems with language processing, while for others it is relatively inconsequential. We were anticipating that there would be two groups - those with intellectual problems and those without. Instead we found a continuum across the children we examined. Some were very, very bright, and some were limited intellectually, and most fell somewhere in between. Yet, across the group, the areas that were weak were consistent, unlike what would be expected in the general population. |
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*** We found that there are some areas that boys with DMD are consistently strong in, including nonverbal skills, abstract reasoning abilities, rote memory and vocabulary comprehension. We also found that tests that require the children to listen to lots of verbal information and process it, or to listen to it and repeat it back, are tests that are selectively impaired in DMD. This was similar to what others had shown, but our results were more detailed than before. We looked among children with normal IQs and saw that even in this group, there were selective difficulties with immediate retention of verbal information. |
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*** We found that what the 6 to 15 year-old boys affected with DMD wish for is similar to what all kids wish for. They long for toys and trips to fun places, and their wish content is not dominated by health-related concerns. That differed from what we expected, but we were heartened with the results - it emphasizes, again, that these boys are CHILDREN first, and have physical and health limitations second. |
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*** We found that the parents of the children with DMD are more stressed than most parents. No great surprise there! But what was surprising was what appeared to contribute the most to parental reports of stress. According to the parents’ report, it was their children’s behavior, rather than their physical limitations, was the thing that accounted for the greatest amount of stress. |
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*** We found that boys with DMD do more poorly than their unaffected siblings on tests of academic achievement such as reading, spelling and arithmetic. This was true even when the sibling pairs had comparable IQ. Moreover, we found that how well they do on measures of verbal span (i.e., how much verbal information they can listen to and immediately repeat back) was the thing that contributed the most to their poor academic achievement. Physical ability, behavior, and problem solving skills had much lesser influences on academic skills. This finding highlights the importance of our earlier work showing that immediate verbal recall skills are limited. On its own, that may not seem too important. After all, if one cannot remember a phone number, one learns to write it down. But the implications of this study are that limited verbal span can have wide ranging effects, including interfering with optimal academic achievement. Our feeling is that children with DMD have a select problem that is not general, but that can have multiple and far ranging consequences. |
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*** We examined verbal and memory skills further in boys and their siblings and replicated our previous finding that many language based skills are not impaired but some are. Specifically, we showed that rote verbal learning (e.g. boys hear a list of items and then have to say them back, and this is repeated five times) is good. With repeated presentation of the list, boys remember more items. Further, their understanding of grammar and word-relationships is strong. However, on tests that ask the boys to listen to and repeat back verbal information (eg., sentence repetition) or where they have to follow verbal instructions exactly as they are presented, the boys with DMD have difficulties. |
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*** We found parents report early language delays as well as motor delays in children with DMD. We think that this is early evidence of the cognitive involvement in the disorder. |
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*** We found that the parents of the kids with DMD report that their children have more social behavioral problems than any other types of behavior problems. As many as 35% of the children in the sample had “clinically significant” behavior problems (parents reported their children often were “immature,” “did not get along with peers”, and were “clingy.” Parents also rated a high number of children with DMD (about 25%) as having attentional problems. The good news was the very limited reports of significant depression, anxiety, and agressive behaviors.
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*** We found that boys with DMD do more poorly than their unaffected siblings recognizing facial affect. The difference was subtle, but real. The two groups did not differ on recognizing faces or objects, but the boys with DMD missed more items where they were asked to match facial emotions. This was true even when the sibling pairs had comparable IQ.
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*** We found that among younger children with DMD the cognitive deficits are more generalized than what we see with the older boys. That is, the children who are still developing their basic language skills struggle on tests of other skills too. This was work completed by Shana Cyrulnik for her doctoral dissertation. |
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Two more recent papers that may be helpful:
*** This paper – written for the neuromuscular community – is a compilation of work and ideas of multiple experts from around the world who have thought about the behavioral presentation in DMD/BMD. The paper is the result of a workshop sponsored by Parent Project Muscular Dystrophy designed to help address areas of care for families with DMD/BMD that have not gotten enough attention. PPMD plans more such workshops in the future with the goal of getting people together to share and talk and disseminate information to those who need it most. |
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*** This paper – written for neuroscientists who study brain function and behavior – introduces the idea of thinking about DMD/BMD as a disorder of a specific part of the brain, the cerebellum. Although for most of you reading this day-to-day life DMD/BMD (and not brain function!) is foremost in your thoughts, most neuroscientists are unfamiliar with the disease. We contend that DMD/BMD should be the focus of more neuroscience research, as it provides an important model of brain function in the absence of dystrophin. This paper presents the cognitive presentation of the disorder along with the evidence of brain involvement and compares what we know about DMD/BMD to what we know about the function of the cerebellum.
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How does this all fit together? Here’s a model of what we believe is going on:
1. The mutated dystrophin gene prohibits dystrophin from being made.
2. The children develop without dystrophin – it is missing from their muscles and their brains.
3. The consequence for the muscles is known and results in progressive weakness. For the brain, it’s less clear, but somehow the result is a lessened ability to listen to and process verbal information. The affected children remember fewer digits and shorter sentences than their unaffected siblings.
4. Day to day, this may not seem too obvious. Over time, however, it may make all verbal learning a little more difficult for the children.
5. If the children aren’t processing school lectures quite as well as their peers, they may not be learning the basic academics as well.
6. Overall, their academic skills are not as strong. Other things may contribute to this too, like fatigue, mood, and physical ability. But our study demonstrated that the measure of verbal span accounted for more of the variance associated with children with DMD doing poorly in academics than any of the others influences. |