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Duchenne Muscular Dystrophy: The Search for New Treatments Races against the Clock


One out of about every 3,500 boys worldwide is born with Duchenne muscular dystrophy (DMD). DMD is the most common as well as the most severe of the more than 30 types of muscular dystrophies, comprising about 50 percent of all cases. Young men with DMD face a difficult life, but they do not face a life without hope.

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Researchers around the world are working on promising treatments, including drug- and cell based therapies, to prolong life expectancy, improve quality of life, and even cure the disease. Joining previous research on improving care and quality of life for DMD patients is a landmark international consensus document, "The Diagnosis and Management of Duchenne Muscular Dystrophy." The document is the result of an extensive review process by 84 international experts in DMD and provides best-practice diagnosis and care standards. It was published in two parts in The Lancet Neurology: part 1, published in January 2010, covers diagnosis and pharmacological and psychological management; and part 2, published in February 2010, cover the implementation of multidisciplinary care. (Author's note: The full document, including parts 1 and 2, can be accessed at www.oandp.com/link/144 )

Previously, there had not been any consensus about how best to care for DMD patients, with care standards differing not only from country to country but also within individual countries, notes CARE-NMD, a three-year project to implement best-practice standards of DMD care across Europe ( en.care-nmd.eu ). The disparity of care approaches has impacted quality of life for boys and young men with DMD, and-because treatments vary from center to center, making it difficult to compare results across multiple centers-it has hindered clinical trials of promising new treatments. "By producing consensus guidelines agreed [upon] by doctors and patient groups across the world, it is possible to...make best-practice care more widespread across the world," CARE-NMD points out.

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What Is DMD?

An inherited X-linked recessive disease affecting males, DMD is characterized by a lack of the protein dystrophin, which causes muscles to deteriorate and break down. About two-thirds of DMD patients inherited the defective gene from their mothers; the remaining one-third of DMD patients have the defective gene because of a spontaneous mutation. (Since females have two X chromosomes, they can be carriers but rarely experience any symptoms.)

DMD usually becomes apparent when the child begins to walk, according to the National Institute of Neurological Disorders and Stroke (NINDS) of the National Institutes of Health (NIH). Degenerating muscle fibers produce progressive weakness and muscle wasting beginning in the upper legs and pelvis and spreading into the upper arms. Children experience some loss of reflexes, a waddling gait, difficulty in rising from a sitting or lying position, overall posture changes, lung weakness, and cardiomyopathy. Some children may have mild cognitive (Continued from page 5) impairment. According to several sources, life expectancy is usually from the late teens into the 20s. On a happier note, however, many young men live into their 30s and 40s, pursue and earn higher education degrees, get married, and achieve personal and professional goals.

The 2010 international consensus document paints a brighter picture for patients with DMD. "Although specific treatments for DMD [currently being researched] have not yet reached the clinic, the natural history of the disease can be changed by the targeting of interventions to known manifestations and complications. Diagnosis can be swiftly reached; the family and child can be well supported, and individuals who have DMD can reach their full potential in education and employment."

The consensus report continues, "Corticosteroid, respiratory, cardiac, orthopedic, and rehabilitative interventions have led to improvements in function, quality of life, health, and longevity, with children who are diagnosed today having the possibility of a life expectancy into their fourth decade."

For instance, corticosteroids can extend the ability of patients to walk by up to two years, according to the NIH.

Orthotist's Role in High-Quality Care

DMD follows a progressive, predictable pattern of independent walking, then assisted walking, followed by wheelchair mobility. Orthotists and physical therapists play a vital role in helping to extend the ambulatory periods.

"I believe every human being cherishes the opportunity of being independent and mobile," says Mark Taylor, MLS, CPO, FAAOP, who works in the Department of Physical Medicine #38; Rehabilitation at the University of Michigan Orthotics and Prosthetics Center (UMOPC), Ann Arbor. "It is devastating to patients and parents alike when this independence starts to disappear in small increments. Proper orthotic intervention can prolong this independence for a short while and provide assistance with mobility and help prevent/delay complications that come with muscles weakening."

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Phil Stevens, MEd, CPO, FAAOP, Hanger Clinic, Salt Lake City, Utah, notes that physicians frequently rely on the orthotist's in-depth knowledge of orthotic technologies and materials for specific orthotic devices to implement a somewhat generalized prescription, thus placing a responsibility on the orthotist to be knowledgeable about the orthotic management of DMD. In 2006, Stevens, a board member of the American Academy of Orthotists and Prosthetists (the Academy) an a member of the Academy's Research Council, published a literature review, "Lower Limb Orthotic Management of Duchenne Muscular Dystrophy," in the Journal of Prosthetics and Orthotics (JPO;www.oanp.jpo ). In the article, Stevens outlines orthotic interventions during the three functional stages of DMD: independent ambulation, assisted ambulation, and wheelchair mobility. He discusses the mechanics of gait and stance and the progression of the disease as it affects mobility. He points out that daytime AFO use places excessive demands on increasingly weakening quadriceps and should generally be avoided. Although proximal weakness is primarily responsible for the end of a child's independent ambulation, extreme equines contractures contribute to this, and Stevens cites evidence that compliant use of nighttime AFOs can slow the progression of equinovarus deformities. Nightime AFOs are often prescribed along with passive stretching regimens.

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"We have to be very careful in bracing Duchenne patients while they are still ambulatory," Stevens says in an interview with The O#38;P EDGE. "I think there is a potential to do more harm than good. There is literature that clearly shows that bracing can make walking much more difficult. For most ambulatory cases, the best approach is to use nighttime orthoses so as to not affect their gait kinematics and kinetics during waking hours."

He continues, "Children with Duchenne muscular dystrophy stop walking due to a combination of lower-limb weakness and increasing contractures. A little bit of plantarflexion contracture can help these children because it helps position the ground reaction forces anterior to the knee, making the children more stable. However, as the contracture becomes more severe, stability is reduced, and patients start walking higher on their toes, finally reaching a point where independent walking is impossible. Many experts recommend nighttime orthoses and/or aggressive physical therapy to control plantar flexion contractures and...prolong the ambulatory period."

Taylor says he has used AFOs for nighttime stretching but has found good compliance a limiting factor and that often orthoses are not used to their fullest potential, a problem Stevens also mentions. "Many parents who are trying to provide comfort for their child have a hard time applying the orthoses when the child complains of pain and discomfort when muscles and tendons are being stretched," Taylor says.

Prolonging Ambulation

When asked about a 1985 study showing a prolonged ambulatory period with related benefits, Stevens says that treatment regimens including aggressive surgeries to release contractures, KAFO application, and standing the first day postoperative, along with studies reporting on the results, were quite common in the 1970s and 1980s in the United States, but he has not seen current reiterations of these studies. He notes that these aggressive regimens are costly and require close coordination and timing among the healthcare team to carry them out successfully; therefore, following these treatment protocols in any setting other than an institutional one is difficult, and the results may not justify the effort and expense, factors that could explain the decline in these procedures in the United States. More information about these protocols is available in the international practice standards consensus document.

In his JPO literature review, Stevens discusses findings that show the benefits of prolonging ambulation, such as preventing or postponing problems associated with wheelchair use in the DMD population, including scoliosis, obesity, disuse atrophy, osteoporosis, pathologic fracture, severe contractures of hip and knee flexors, and further foot and ankle deformity, along with benefits to gastrointestinal and pulmonary function and psychological well being.

Regarding KAFO use, Taylor says, "I have seen both positive and negative results in providing KAFOs to Duchenne patients. Modern technology has allowed the orthotist to use stronger and lighter materials in designing and providing orthotic intervention to these patients. However, the orthotist needs to understand in detail the effects of biomechanical control and how it can affect the control of lever arms in the lower extremities position of the lower trunk. Too much control can limit the dystrophy patient in the ability to stay upright and stable." He adds, "I believe our technical staff has now worked with carbon fiber long enough to understand how to use it and keep the function of the orthosis strong and yet lightweight, which is necessary when applying KAFOs and AFOs to muscles that are continuing getting weaker.

"In the third stage, wheelchair mobility, Stevens notes that some authors point out the value of postoperative nighttime AFOs to prevent recurrence of deformity after corrective surgery. In describing the value of nighttime AFOs in controlling equinus contractures for pain management, he says, "Severe equinus plantar flexion contractures can be painful, and in extreme cases the foot can actually sublux.

"Taylor adds, "There are strong benefits when applying orthotic intervention properly. It needs to start early, and close follow-up needs to be a part of the total medical plan. Even though muscles are getting weaker, there is still bone growth, and whatever orthotic plan is initiated, adjustment needs to be made to accommodate for growth and continued comfort.

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"Orthotists need to become very familiar with the pathology of Duchenne muscular dystrophy and the pathway it takes," he continues. "They need to be available for their patients and have the ability to communicate with other members of the healthcare team as to what is needed and at what time it is needed. Waiting too long to make a decision can void an opportunity for enhanced stability and quality of ambulation."

International Consensus

The international consensus document on DMD bestpractice standards includes the following findings on orthotic management:

Research Moves Forward

Just as following best-practice care standards when working with patients with DMD enhances function and quality of life, ongoing research offers hope for better therapies and even possibly a cure. Initiatives, among others, include the following:

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Resources for Patients, Families

A well-known English proverb states, "A trouble shared is a trouble halved." Although a DMD diagnosis can leave parents feeling alone and overwhelmed, there is an abundance of resources and support mechanisms available to help parents-and the young patient himself when he is old enough to understand his condition:

Miki Fairley is a freelance writer based in southwest Colorado. She can be reached at miki. fairley@gmail.com Copyright 2012 Western Media/The O&P EDGE. All rights reserved. Reprinted with permission.