The failure of a gene on the X chromosome to make a necessary protein called dystrophin, says the Muscular Dystrophy Association (MDA) is the cause of Duchenne Muscular Dystrophy (MD) — with a milder form, called Becker Muscular Dystrophy, being the result of dystrophin that is in too short supply or damaged.
Boys with Duchenne MD — and Duchenne patients are nearly always boys, since a girl with one damaged X chromosome usually can count on her other X chromosome to supply enough dystrophin — experience a range of difficulties not restricted to mobility. Seating & mobility professionals working with them frequently face difficulties of their own, as they work to recommend and build systems that will serve these clients and their families both today and tomorrow.
Duchenne MD in Early Years
In explaining the impact of Duchenne MD, Lauren Rosen, MPT, ATP, Motion Analysis Center, St. Joseph’s Children’s Hospital of Tampa, says the condition results “in basically the musculature dying off. The first joints that we tend to see it in are the hips, the pelvis, the thighs and the shoulders, which of course are your big stability muscles and joints. That’s why it causes so many problems.”
Ryan Hagy, MOT, OTR/L, ATP, sales director for Quantum Rehab in the western United States, says children with Duchenne MD typically show normal development for the first few years of life. “Then somewhere on average between the ages of 3 to 6 (years),” he says, “you’ll start seeing things like falling, or more difficulties doing the gross motor activities, like running and jumping. They just appear more clumsy, and it’s actually because they’re fatiguing, or their muscles lack the strength to perform those activities.”
Young children with Duchenne MD initially find ways to adapt to walking. Rosen says, “These kids tend to get very hypertrophied calves, so a lot of them end up with plantar flexion contractures, so they walk on their toes when they’re still walking.”
Still, walking becomes harder and harder for them.
“As they start getting weak, ambulation is one of the first things Handbook to go, because with very weak hips, they tend to arch their backs and hang on these ligaments on the front of your hips called your Y ligaments,” Rosen says. “They hyperextend their knees to balance themselves, but usually by 9 or 10 (years) at the latest, these kids are losing the ability to walk because of strength and stability.”
Moving Into Mobility Equipment
Even prior to that eventuality, Duchenne patients may benefit from mobility equipment, Hagy says.
Upon diagnosis, he notes, boys “may not need mobility equipment right away, because they can still navigate their home, their classroom and their environment. Then it becomes more a strength and fatigue issue, where they can maybe still get around inside their house, but they’re not going to traverse long distances across the school or go out in their community. That’s really where clinicians and providers start looking at a manual chair, because (the children) can maybe assist with propelling themselves, and it’s really about getting around long distances. They can still do most of the short stuff on their own.”
By the time kids with Duchenne start school, Rosen says, “they start experiencing the effects enough that they’ll maybe use a wheelchair part-time in the 6- to 7-year-old range.” Even then, she adds, they typically seek propulsion assistance: “That’s usually more of mom and dad pushing them, and doing a little bit of pushing of the manual chair themselves, but not a lot.”
From there, Hagy says, clinicians usually see “a pretty quick transition” from manual chair use to power chair use, “just because of how rapidly (Duchenne MD) progresses. To maintain independence and maximize their function and quality of life, get them in a power chair as soon as you can and let them maintain their mobility.”
Decisions that Can Evolve
At this point, of course, clinicians and providers find themselves faced with some of the most difficult questions: How quickly will the child progress? What adaptability does the power chair need to have?
Rosen says that relatively speaking, kids with Duchenne do progress in a fairly predictable way: “When somebody comes to see me at (age) 4, I know what kind of chair I’m going to do, versus somebody who comes to see me when they’re 10. I’m very picky about the chair I use from that perspective, so I know I’m picking something that I can easily put specialty controls onto and that will accept a vent. If I need to add another power function to it, I can do that without having to replace an entire seating system.”
Noting that funding sources in general prefer to work with current situations rather than future ones, Rosen adds that as she plans out a mobility system, “I don’t plan for it as in asking right then for a vent tray. There are certain chairs that accept vent trays better than others, and even within (the same) manufacturers, certain models will accept specialty controls, whereas other models won’t.”
Seating kids with Duchenne MD, Rosen says, is another huge challenge. “The tendency is to give them a lot of positioning support because they do get the weakness,” she says. “The problem is kids with Duchenne have a tendency to pull away from a lot of support, like a lot of the custom-molded systems that are out there. A lot of those kids can’t tolerate them at all.
“I think it’s two things: Because they have full sensation, they just don’t like the sensation of having something all around them. And when you do really position somebody well, you take away their ability to change their position slightly for function. So sometimes when we over-support them, we take away function, and they start pulling away from it. A lot of them end up slowly but surely going anterior to whatever support we put behind them until they absolutely can’t do it anymore, and all of a sudden we’ve got to give them tilt. They’re so used to leaning forward that leaning back against the system is very complicated, difficult and uncomfortable for them.”
Rosen says she’s found more success with less-obtrusive, more breathable backs when clients have needed custom-molded support. But she still faces significant challenges in those situations.
“I’ve been seating some older teens and (adults) in their low 20s, and when I start talking about anything custom molded, they all say, ‘Not that! A therapist did that to me five years ago, and it was the most miserable experience of my life.’ I have to explain to them: ‘I’m not trying to fix you. I’m trying to support you where you need to be.’ I think that’s the difference: Making sure that we’re really taking function into account when we’re picking supportive equipment for them.”
Duchenne also decreases respiratory function, which also impacts a seating & mobility system, Rosen says. Muscle strength is lost, she says, “proximal to distal, so you lose (strength in) shoulders and hips, and then at the same time, you’re losing function in your trunk.” Children with Duchenne, she explains, “don’t just breathe with their diaphragm. It’s weak, so they use some of their rib musculature and their shoulder musculature to breathe. And if we lock a kid into a seating system that doesn’t allow them any chest expansion, we’re limiting their ability to breathe. I think we forget about the breathing (factor), because we kind of know these kids are going onto a vent. The vent’s going to breathe for them eventually, anyway. But I think the longer we can keep them off the vent, the better for everybody.
“If these kids are potentially going onto a vent — which 99 percent of these kids do before they pass away — as I’m developing a seating system, I’ve got to be designing a system that I know can take a vent tray and that can support the equipment they’re going to need. Also, most of these kids, before they go onto a vent, they’re also going to specialty controls. They’ve lost the ability to use a normal joystick, and either we’re going to some kind of a mini joystick, or sometimes fiber optics. I don’t do a lot of chin (controls) with Duchenne; they tend to not do real well with that, I think because of the trach that’s coming right around the same time. They’re really losing a lot of that function. But it’s really just making sure that the system I’m designing can accommodate whatever’s going to happen.”
Options for Becker Muscular Dystrophy
Clients with Becker MD present their own challenges. On the one hand, the slower progression of Becker MD means patients retain strength and stamina longer. On the other hand, progression tends to be less predictable than with Duchenne.
For instance, while it would seem out of the question for boys with Duchenne MD to operate scooters, boys and young men with Becker MD might find scooters a good choice, at least for part-time mobility. Says Hagy: “Depending on how slow we’ve seen the progression, and if they only are going to need it to go long distances, yet they’re not going to propel a manual chair — and if they don’t need a lot of trunk support or don’t have transportation for a power chair — maybe then scooters are an option.”
When creating a mobility system for a child with Duchenne MD, Hagy says, “right away, you’re building in the expandability for it, different seating options, different electronics, growth. Versus a young adult diagnosed with Becker — you’re still going to want to take those things into consideration, but you’re not going to be as certain that they’re going to progress from a joystick to an alternate drive control in the next two, three or four years.”
Function, Function, Function
While kids with Duchenne MD lose their muscle strength predictably and rapidly, Rosen still emphasizes the importance of preserving function wherever possible.
For instance, she says: “These kids should stand as much as they possibly can. As soon as they’re losing the ability to walk, they really should go into standers. There has been research that has shown that standing has helped prolong life and postpone some of the ill effects. Our bodies just function better in standing. It can help digestion, it opens up your chest better for breathing. Some of it also may be psychological; people feel better in the upright position than if they’re sitting all the time.”
“Activity is certainly encouraged,” Hagy says. “You’re not trying to over-fatigue or overstress the muscles, but you definitely want (patients) to be active and not only to maintain muscle use, but you also look at the joints and range of motion, because contractures are becoming an issue with these children as well. If you stop using the muscles, you stop moving the joints, things start binding down, and it becomes more of a positioning issue for wheelchairs or lying in bed or whatever comes down the road. So activity is encouraged to keep them mobile, but also to keep their joints free moving.”
Hagy pauses, and then adds a last vote for maintaining function as long as possible. “They’re still young boys,” he says, “so they do youngboy things.” He mentions routinely seeing Duchenne MD patients starting spontaneous games of wheelchair rugby in the halls of seating clinics and adds, “They can be a fun bunch to work with.”