Chapter 51 Muscular Dystrophy
PATHOPHYSIOLOGY
The muscular dystrophies constitute a group of muscle diseases characterized by severe muscle weakness and atrophy, elevation of serum muscle enzyme levels, and destructive changes of muscle fibers. Affected muscles pseudohypertrophy, and the muscle tissue is replaced by connective tissue and fatty deposits. The traditional classification into Duchenne’s muscular dystrophy (DMD), Becker’s muscular dystrophy, limb-girdle dystrophies, and congenital dystrophies has become more precise with advances in genetics and the ability to identify specific defective proteins.
The most common form of muscular dystrophy (MD), Duchenne’s, is a sex-linked recessive disorder, with mutation of the dystrophin gene and deficiency or absence of dystrophin in skeletal muscle. Onset of symptoms is between 3 to 5 years of age. It is characterized by progressive involvement of voluntary muscles: clumsy gait, lordotic posture, calf hypertrophy, and toe walking are early manifestations. Children with DMD rarely live beyond 20 years of age without mechanical ventilatory support.
Becker’s MD is a sex-linked recessive disorder that involves a reduction in dystrophin, and it is the second most common form. Onset is between 5 and 15 years of age, with survival into the fourth or fifth decade.
Emery-Dreifuss muscular dystrophy (EDMD) has two genetic forms, an X-linked recessive form and a less common autosomal dominant one. EDMD is associated with mutations in emerin, a nuclear membrane protein. Symptoms begin within the first 2 decades of life. Muscle wasting of the biceps and triceps occurs and progresses to include pectoral and pelvic muscles. Typically early development of contractures and cardiac conducton defects occurs.
Limb-girdle muscular dystrophies may be autosomal dominant, autosomal recessive, or congenital. Diagnosis is made by identifying the missing protein with muscle biopsy. Symptoms are a slow onset of progressive muscle weakness; the age of onset varies.
Fascioscapulohumeral muscular dystrophy is the third most common type of MD; it usually begins in the second decade of life. It is an autosomal dominant disease. Muscle biopsy results vary. Clinical symptoms include the classic scapular winging as a result of early weakness of the scapular muscles.
INCIDENCE
1. DMD affects 1 of every 3000 boys (X-linked recessive). Rarely, girls can be affected.
2. DMD accounts for approximately 50% of all cases of muscular dystrophy.
3. Becker’s MD affects boys and occurs in approximately 1 in 30,000 to 40,000 male births. Limb-girdle MD has approximately the same incidence.
4. Fascioscapulohumeral MD affects both sexes.
5. Approximately 30% of the sisters of boys with muscular dystrophy will be carriers, and one half of their male offspring will inherit the disease.
6. Learning disabilities and mild mental retardation are not uncommon in MD.
7. Female carriers of DMD are at risk of developing cardiomyopathy and require periodic cardiovascular screening.
CLINICAL MANIFESTATIONS
Symptoms are related to the voluntary muscles that are affected. The most frequently occurring symptoms are the following:
3. Waddling gait or toe walking
4. Gowers’ sign (hands “climbing” up legs when arising from sitting position)
5. Difficulty running, clumsiness
6. Difficulty lifting arms above head owing to involvement of shoulder girdle muscles
7. Often, loss of ambulation by age 8 to 12 years (Duchenne’s) or 40 years (Becker’s)
8. Pseudohypertrophy, particularly of calf muscles, giving a hard, “woody” appearance
9. Occurrence of scoliosis after child becomes wheelchair dependent
MEDICAL MANAGEMENT
A comprehensive, interdisciplinary team approach is used in the long-term management of MD in children. Generally, an interdisciplinary approach with participation of specialists in neurology, orthopedics, physical and occupational therapy, psychology and/or social work, and nursing is used. In those with Duchenne’s MD, spinal fusion is usually performed in early adolescence or when the curvature is between 30 to 50 degrees. Optimal timing for surgery is while lung function is satisfactory and before cardiomyopathy is severe enough to increase the risk of an arrythmia occurring under anesthesia.
Respiratory management requires periodic evaluation including pulmonary function studies, patient education, and decision making about what mechanical ventilatory support is desired. Typically, normal pulmonary function fails, resulting in ineffective cough, inadaquate nighttime ventilation, and then inadequate daytime and nighttime ventilation as the disease progresses. Appropriate mechanical support can prolong and improve quality of life. Cardiac evaluation should be done upon diagnosis and at least biannually starting at age 10 years or with presentation of symptoms. Some studies claim to show benefit from the use of steroids in the treatment of DMD, increasing muscle strength and function as well as prolonging pulmonary function. Controversy persists, however, and steroid use is not yet uniformly recommended. Ongoing research supports the use of gene and cell therapies, but this treatment is not considered ready for clinical practice.
NURSING ASSESSMENT
1. See the Musculoskeletal Assessment section in Appendix A.
2. Assess child’s adherence to physical therapy regimen.
3. Assess child’s and family’s adherence to pulmonary regimen.
4. Assess child’s level of self-care functioning.
5. Assess child’s and family’s level of coping (refer to Appendix F).
6. Assess child’s and family’s management of home treatment regimen. Assess home equipment needs.
7. Assess child’s and family’s need for information.
8. Consult with school nurse to assess for special accommodations needed at school (see Appendix G).
NURSING DIAGNOSES
• Growth and development, Delayed
• Constipation (related to decreased mobility)
• Nutrition: more than body requirements, Risk for imbalanced
• Family processes, Interrupted
• Diversional activity, Deficient
• Self-care deficit, Bathing/hygiene
• Self-care deficit, Dressing/grooming
• Self-care deficit, Toileting
NURSING INTERVENTIONS
1. Advise use of braces and splints as indicated to avoid contractures.
2. Advise consumption of high-fiber, low-fat diet with adequate water intake.
3. Advise use of breathing aids to assist in gas exchange.
4. Assist parents in expressing and working through feelings of guilt, resentment, and anger.
5. Encourage and support parents seeking genetic counseling and support in self-care and health maintainance.
6. Encourage parents and siblings to mourn (loss of “perfect” child) and to learn to cope.
7. Encourage participation in academic and peer support groups (see Appendixes F and G).
8. Advise importance of avoidance of secondhand smoke, routine immunizations, and annual influenza immunization.
Discharge Planning and Home Care
1. Promote optimal muscular functioning.
2. Promote self-care activities as means of enhancing child’s sense of independence and self-sufficiency.
3. Encourage parents, in collaboration with child, to select realistic goals for achievement and living.
4. Provide support for child and family as they cope with disease.
5. Provide information about and make referrals to available educational resources (see Appendix G).
6. Provide information and assess long-term care needs pertaining to the following:
CLIENT OUTCOMES
1. Child will maintain optimal physical mobility.
2. Child will maintain optimal cardiopulmonary function.
3. Child will maintain inclusion in social, educational, and recreational activities as able.
4. Child and family will make informed decisions about treatment and management of the disease including respiratory support, end of life issues, and advance directive.
5. Child and family will express feelings as disease progresses.
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