Duchenne Muscular Dystrophy

Introduction

Muscular dystrophy is a group of neurodevelopmental, genetic disorders that are characterized by the progressive wasting and weakness of voluntary muscles and includes different forms, each with a unique set of characteristics.¹ Specifically, variation between forms may include the types of muscles involved, the age at which symptoms appear, how fast the disorder progresses, and how the disorder is transmitted from one generation to the next.¹

Etiology

Duchenne Muscular Dystrophy (DMD) is a disorder described as a progressive wasting of the muscles leading to muscle weakness and loss of function.¹ It is caused by a mutation of an x-linked gene that is associated with the protein dystrophin. DMD occurs when the gene on the short arm of the x-chromosome fails to make dystrophin, causing the glycoprotein structure of the muscle sarcolemma to be less stable and lose its integrity, which then leads to muscle damage.² DMD occurs almost exclusively in males, however, it can occur rarely in females. In these cases, the female would likely carry mutant genes on both x-chromosomes or have an inactivated, healthy x-chromosome.³

Prevalence

DMD is the most prevalent of the muscular dystrophies and it can vary in different populations.¹ It occurs in approximately 1 in 3,300 male births and 1 in 50,000,000 female births. Although it is extremely rare for females to have DMD, many are carriers of the disorder but do not exhibit signs or symptoms.³

Signs and Symptoms

The most common sign and symptom of DMD is progressive muscle weakness leading to loss of function.³ The muscles in individuals with DMD are affected at birth and symptoms of muscle weakness usually begin between the ages of 3 and 5 years. Voluntary muscles of the arms, legs, and trunk are affected first, while the heart and respiratory muscles are affected later in life.² Progressive weakness is evident as the child’s motor functions are affected, resulting in decreased balance, awkward gait, frequent falls, and difficulty climbing stairs.¹ Gross motor functions such as walking, running, jumping, and hopping are delayed and very difficult for the child. Children with DMD may begin walking by 18 months of age, which is a later age than most children. Toe walking is also a common sign of DMD, and at times it may not be clear that the child’s walking pattern is different from others. However, when compared to other children or siblings, the muscle weakness is very visible.² Pseudohypertrophy (enlarged calf muscles) and joint contractures in the lower extremities may also develop.¹ As pelvic muscles become affected, lumbar lordosis is evident, resulting in an awkward posture and a Trendelenburg gait. Trendelenburg gait is an abnormal gait associated with a weakness of the gluteus medius. It is characterized by the dropping of the pelvis on the unaffected side of the body at the moment of heelstrike on the affected side⁴. Children with DMD also have difficulty standing up, therefore they use what is known as the “Gower maneuver” to stand up. This involves the child using their upper extremity to get themselves up by first getting on their hands and knees and then by “walking” their hands up their legs until they are in an upright position. A noticeable sign of DMD is also frequent falls of the child due to the muscle weakness.⁴ Later in the child’s life, upper extremities are affected resulting in difficulties relating to self-care needs; this is evident as the child is unable or struggles to raise his/her arms.²

Along with motor delays, children with DMD may have language development delays. Furthermore, they may have significant cognitive deficits such as high distractability, poor attention span, immaturity, fear of new situations, obsessive-compulsive disorder features, and learning difficulties in school.² However, unlike motor function, cognitive deficits do not deteriorate over time. Children with DMD also tend to be creative and artistic, which is likely due to their decreased motor abilities.²

Due to scoliosis caused by DMD, children usually require spinal surgery to correct the curvature. In addition, by their mid to late teens, the child often requires respiratory ventilation due to pulmonary issues.² Approximately half of the children with DMD experience heart deficits such as extreme tachycardia. Death often occurs in their late teens to early 20’s from respiratory-related illnesses (75%) or left ventricular failure (25%).²

Progression of DMD

3-5 years: muscle weakness begins first in the lower extremities²
6 years: toe-walking, waddling, unsteady gait, frequent falls²
8-12 years: begin to use wheelchair full time²
3-4 years after loss of ambulation: 90% develop a spinal curvature of greater than 20 degrees²
9-11 years: pulmonary function is affected resulting in respiratory issues and often pneumonia²
Mid-teens: upper extremities become affected and children lose self-care abilities²
Mid-teens to early 20’s: death may occur due to respiratory or heart related illness²
Note: Due to medical advances individuals with DMD are living longer⁴

Implications for Occupations - Self-care, Productivity, and Leisure

As muscles begin to deteriorate, gradual loss of independent function in self-care, productivity, and leisure will occur.⁴

Self-care

Self-care activities include showering, brushing one’s teeth, dressing, and eating during which upper limb function is crucial for independence.⁴ Muscle weakness, poor grip strength, and increasing difficulty lifting hands and arms against gravity are major challenges to self-care occupations.⁴ The strength and endurance required to maintain a raised arm posture for showering or brushing one’s teeth, for example, will become a challenge. In later stages of DMD, an individual will become completely dependent in toileting needs.⁴ Loss of muscle function as well as loss of ability to control bowel movements and incontinence will eventually occur.⁴ Loss of range of motion (ROM) is another characteristic of DMD that will impact self-care activities⁴. The activity of eating, for example, is heavily dependent on upper limb function. The ability to grasp and manipulate cutlery and cups requires fine motor ability as well as ROM, strength, and endurance.⁴ Sleeping is another area of self-care that is impacted by the progression of DMD.⁴ Maintaining proper positioning during sleep is essential to prevent contractures and spinal curvatures that can impact respiratory function.⁴ Sexuality is an area that is often overlooked by health care professionals; this can be addressed by an occupational therapist as a person with DMD enters adolescence.⁴

Productivity

An individual with DMD will face challenges in occupations relating to productivity. For children, play or exploration of the environment, as well as school activities, are the primary occupations of productivity.⁵ Play develops skills such as proprioception, coordination, and appropriate social interaction.⁵ It is important to provide opportunities to develop these skills through play prior to the intermediate stages of DMD.⁴ Participating in school activities is another imperative part of childhood. Reduced strength, ROM, stamina, and postural and co-ordination difficulties directly impact the ability to participate in classroom activities.⁴ Handwriting is a major occupation involved in school participation, and difficulties with pencil grip and co-ordination may impair a child’s ability to write properly.⁵ This can be addressed through the exploration of different methods of written communication in order to prevent hindrances in academic development⁵. Deficits in language development may also be evident and this will affect the child's ability to communicate with others in the school environment.⁴ In addition, memory and attention difficulties will affect the child’s ability to learn and carry out requests.⁴ Due to medical advances, people with DMD are living longer; therefore, employment opportunities may become a challenge.⁴ Difficulties with employers, interviews, work adjustments, and discrimination are some barriers an individual with DMD may face.⁴

Leisure

Leisure occupations are based on individual interests and may include play, sports, hobbies, and social interaction. These occupations may be hindered due to the progressive nature of DMD.⁴ Interaction with the environment and participation in activities of interest is possible, especially in the early stages of the condition. Health care professionals ^4p111suggest, “participation in sports gives opportunities to develop a competitive spirit, self- discipline, and a way of making new social contacts, which can help raise self-esteem and reduce social isolation.” However, as the condition progresses, participation in high-impact activities will decline as an individual’s ability declines. It is recommended to avoid repetitive muscle building-types of activities, as it may further damage healthy muscles tissues.⁴ There are a number of low-impact activities that can be carried out with different levels of ability, such as photography, gardening, using the computer, and playing video games. Family and friends are the most important factors to maintaining an active social life. Social activities facilitate self-worth, confidence, and a sense of belonging.⁵ These may include spending time with friends or going on a vacation. It is important to include leisure activities in an individual’s life and to be aware that over-protective attitudes of friends and family can negatively affect opportunities for leisure activities.⁵

Progression of DMD - Impact on Occupations

Gradual loss of independent mobility affects all areas of occupation.⁵ Deterioration of lower limb muscles in initial stages of DMD will cause difficulties with balancing and executing complex movements such as hopping or skipping.⁴ The ability to participate in games that require such movements will be affected as falls become more frequent. Adopting a Trendelenberg gait or toe-walking to compensate for weak pelvis muscles will affect the ease of mobility.⁴ Some self-care activities, such as showering, may become unsafe. Full-time use of a wheelchair is typical between the ages of eight and twelve and additional challenges will arise at this time.⁴ Methods of transportation to, from, and within a child’s school, their participation in leisure, and their ability to access certain physical environments are areas that will need to be addressed.⁵

How Occupational Therapy Can Address Identified Occupational Performance Issues

The goal of occupational therapy is to obtain a clear understanding of the individual, of their social circumstances, and of their environment in order to develop a treatment plan that will improve their quality of life.⁴

As previously discussed, individuals with DMD often experience difficulties in areas of self-care, productivity, and leisure. This is related to the effects of the disorder, such as decreased mobility, decreased strength and postural stability, progressive deterioration of upper-limb function, and contractures.⁴

Occupational therapists address an individual's occupational performance issues by using different assessments and resources such as splinting, bracing, manual muscle testing (MMT), ROM, postural intervention, and equipment prescription.⁶

Splinting and Orthoses

Splints, also referred to as orthoses, are designed to maintain or improve ROM, prevent deformity, and improve function. Splints help to support and keep limbs stretched, which delays or prevents the onset of contractures that commonly affect the knees, hips, feet, elbows, wrists, and fingers.⁶ An ankle foot orthoses (AFO) can be used during sleep or during the day. The purpose of this is to keep the foot from pointing downward and sustain the stretch of the achilles tendon.^6,7 Maintaining the length of the tendo-achilles, also referred to as the gastrocnemius-soleus complex, is extremely important. Knee ankle foot orthoses (KAFO) are also used for walking or for standing and can be used to prolong ambulation or help delay the onset of lower limb contractures.⁶

Manual Muscle Testing and Range of Motion

MMT is used to evaluate muscular strength, whereas goniometry or ROM tests measure movement around a joint. Both methods help delay contractures by stabilizing the joint and preventing tendons from shortening.^6,7 Passive ROM combined with the use of night splints can significantly improve tendo-achilles contractures.⁷

Seating and Postitioning

Proper seating is essential to prevent spinal curvatures. Severe scoliosis is common in DMD and can interfere with sitting, sleeping, and breathing.⁸ A wheelchair that is fitted appropriately accounts for frame size, type of seat, lumbar support, and cushioning to avoid pressure ulcers.⁴ It should be equipped with other mechanical devices, such as tilt ability, in order to provide comfort and to protect the skin. Power wheelchairs are indicated for most clients who can no longer ambulate, as they do not have enough upper extremity strength to propel a manual wheelchair independently.⁴ DMD affects many people in their adolescence, therefore, it is crucial for occupational therapists to be conscious that significant development may occur during this time.⁸ Without proper seating and postural support throughout development, deformation may occur, which could result in dysfunctional positioning. It is important for occupational therapists to re-evaluate the fit of an individual’s wheelchair as often as every year during adolescence.⁸

Adaptive Equipment and Devices

Alternate mobility options, positioning aids, and equipment that occupational therapists prescribe include walkers or quad-canes that are used for individuals who are able ambulate as they reduce the risk of falling. In addition, transfer boards, mechanical lifts, and specific transferring education are important because fractures have been seen to occur during transfers as a result of osteoporosis.⁹ Handheld shower heads and bath benches are indicated to enable individuals to manage their own self-care needs as much as possible.⁹ Individuals who are able weight bear and take a few steps may utilize commode chairs, thus giving them the ability to toilet independently.⁹ To compliment an individualized wheelchair, an occupational therapist may also consider prescribing a hospital bed, pressure-relieving mattresses, and foam wedges for proper positioning to prevent pressure skin ulcers, contractures, and deformities.⁴

Social Skills Development

Along with physical difficulties, individuals with DMD may have social issues that an occupational therapist can assist them in overcoming.⁹ Group sessions or individualized programs that focus on coping mechanisms for depression are examples of what an occupational therapist can facilitate.⁹ Self-esteem building for individuals of all ages is an essential part of ensuring that a high quality of life is achieved.⁹ Occupational therapy intervention can play an essential role in supporting the development of social skills through group interactions and other life experiences.⁹ An occupational therapist can use a variety of psychosocial frameworks for developing strategies and techniques for individuals to utilize, which will help them work through various psychosocial issues they may be experiencing.⁴

Sexual Health

Sexuality is a topic that many people feel uncomfortable discussing and thus may be overlooked by health care professionals. An occupational therapist will educate individuals with DMD on safe and effective ways to experience their sexual life.⁴ Such education can include various forms of sex as well as numerous positions that they would be able to perform.⁴

Employment

Gaining and maintaining employment can be difficult for individuals with DMD. An occupational therapist may collaborate with an individual, employer, and case manager to ensure that the individual’s work environment is as enabling and accessible as possible.⁴ By adapting the physical work environment, the social environment, and the work requirements and guidelines, an individual can maintain meaningful employment as well as be as an asset to his or her employer. This may not only impact the individual’s perceived self-efficacy but also his or her financial well being.⁴

Home Modifications

Maintaining independence is often a main focus of occupational therapy interventions if it is a priority of the client. Within the home, there are numerous obstacles that may prevent a client from being as independent as possible. Home modifications and adaptations are something that an occupational therapist can assist with.⁴ Such modifications may include: railings for safe mobility and transfers, lifts, adapted kitchens that are accessible for wheelchairs, and bathroom modifications such as raised toilet seats or modified baths.⁴

Leisure

An occupational therapist can support individuals with DMD to find leisure activities that are meaningful for them to participate in; accommodations and adaptations can be made to enhance participation.⁴

Advocacy

In order to create a successful therapeutic relationship it is important to coordinate with family members, friends, and other social resources to ensure that a person with DMD has both physical and emotional support. An occupational therapist can act as an advocate for his or her client and can educate those around him or her regarding information about the illness, supports, resources, and other concerns.⁴ An occupational therapist can also provide his or her client with the tools to learn how to advocate for him or herself.⁴

Conclusion

DMD is a neuromuscular genetic disorder characterized by the progressive wasting of the muscles leading to muscle weakness and loss of function.¹ Due to the progressive deterioration of muscles, all areas of occupation including self-care, productivity, and leisure are impacted.⁴ Occupational therapy can play a significant role in DMD rehabilitation by supporting individuals to improve or maintain quality of life through both remediation and compensation.⁴

References

¹Muscular Dystrophy Canada. About muscular dystrophy [Internet]. 2011 [cited 2011 March 10]. Available from http://www.muscle.ca/en/western-canada/muscular-dystrophy.html.

²Biggar WD. Duchenne muscular dystrophy. Pediatrics in Review. 2006; 27(3):83-88.

³General Practice Notebook. Duchenne muscular dystrophy [Internet]. 2010 June [cited 2011 March 10]. Available from http://www.gpnotebook.co.uk/simplepage.cfm?ID=-885719035.

⁴Stone K, Tester C, Howarth A, Johnston R, Traynor N, McAndrew H, et al. Occupational therapy and Duchenne muscular dystrophy. Hoboken, New Jersey, United States of America: John Wiley & Sons Ltd; 2007.

⁵Rodger S, Ziviani, J, editors. Occupational therapy with children: understanding children's occupations and enabling participation. Oxford: Blackwell Publishing Ltd; 2006.

⁶Kinali M, Manzur AY, Muntoni F. Recent developments in the management of Duchenne muscular dystrophy. Paediatrics and Child Health. 2008; 18(1):22-26.

⁷Hyde SA, Fløytrupa I, Glentb S, Kroksmarkc A, Sallinga B, Steffensena BF, Werlauffa U, Erlandsend U. A randomized comparative study of two methods for controlling Tendo Achilles contracture in Duchenne muscular dystrophy. Neuromuscular Disorders. 2000;10(4);257-263.

⁸Richardson M, Frank A. Electric powered wheelchairs for those with muscular dystrophy: Problems of posture, pain and deformity. Disability and Rehabilitation: Assistive Technology. 2009;4(3):181-188.

⁹Wagner K, Lechtzin N, Judge D. Current treatment of adult Duchenne muscular dystrophy. Biochimica et Biophysica Acta. 2007; 1772:229-237.