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November 19, 2008

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The Education of Children with Neuromuscular Disease:
A Guide for Teachers and Parents

Chapter 6: Characteristics and Medical Management of Neuromuscular Diseases

Examples of Neuromuscular Diseases and Prevalence

Neuromuscular diseases are disorders of the neuromuscular system which includes four components:

• Anterior horn cells llocated in the spinal cord,
• Motor and sensory fibers of the peripheral nerves between the spinal cord and body muscles,
• Skeletal, cardiac and small muscle fibers, and
• Junctions between the muscle and nerve fibers, the myoneuroal junctions.

Diseases may be inherited (hereditary) or acquired. Hereditary disorders are x-linked recessive, autosomal recessive and autosomal dominant. Examples are shown in Table 1. Over 200 neuromuscular diseases have been reported.

Table 1. Examples of Childhood Onset Neuromuscular Diseases.

Affected Component		Etiology
		Hereditary	Acquired
Muscle		- Muscular dystrophies Becker's Duchenne Emery-Dreifuss Facioscapulohumeral Limb-Girdle Myotonic (Steinert's) - Metabolic myopathies	-Polymyositis -Dermatomyositis
Peripheral Nerve and Motor Nerve Roots		- Hereditary Motor & Sensory Neuropathies Charcot-Marie-Tooth Dejerine-Sottas disease - Friedreich's ataxia	-Physical injury -Accompanying disease, such as diabetes -Guillain-Barré syndrome
Myoneural Junction		- Hereditary myasthenia gravis	-Myasthenia gravis -Botulism -Lambert-Eaton syndrome
Anterior Horn Cell		- Spinal muscular atrophy	-Poliomyelitis and post-polio muscular atrophy syndrome

With the excepton of some of the acquired diseases such as peripheral nerve trauma or injury secondary to an accompanying disease like diabetes, most neuromuscular disorders are rare. Table 2 shows the prevalence of some of the hereditary diseases.

Table 2. Prevalence of Some Neuromuscualr Diseases.

Disease	Estimated Prevalence, per Million (Range)	Estimated Number in Year 2000 in U.S.
Hereditary Motor and Sensory Neuropathies	100 (14 – 282)	28,142
Duchenne Muscular Dystrophy	63 (19-95)	17,729
Myotonic Muscular Dystrophy	50 (9 – 96)	14,071
Becker's Muscular Dystrophy	24 (6 – 27)	6,754
Limb-Girdle Muscular Dystrophy	30 (3-44)	8,442
Facioscapulohumeral Muscular Dystrophy	15 (2 –70)	4,221
Spinal Muscular Atrophy: Intermediate and Juvenile	12 (2 – 42)	3,377

General Characteristics of Most Neuromuscular Diseases

It is beyond the scope of this Guide to describe even the more common diseases. Excellent resources for this information are on the web site of the Muscular Dystrophy Association ( www.mdausa.org ) and the Neuromuscular Disease Center, Washington University, St. Louis ( www.neuro.wustl.edu/neuromuscular ). Genetic patterns (genotypes) are extensive in many of the neuromuscular disorders. For example, there are at least 11 gene locations for just limb-girdle dystrophy. Fortunately, the clinical characteristics (phenotype) are more homogeneous and can often be clustered. In limb-girdle dystrophy, only one genotype presents with a rapidly progressive and severe weakness with advanced secondary conditions such as contractures and spinal deformity. The others are slowly progressive.

Table 3 reviews the effect of neuromuscular diseases on the various body systems.

Table 3. Effect of Neuromuscular Diseases on Body Systems.

BODY STRUCTURE	BODY FUNCTION (IMPAIRMENT)	ACTIVITY LIMITATION (FUNCTION)	PARTICIPATION RESTRICTION
Skeletal Muscle	Functional muscle mass Skeletal muscle fibrosis Strength Endurance Fatigue	Mobility (walking, running, wheeling) Upper extremity tasks (reaching, throwing) Fine motor tasks (writing, typing, object manipulation) Self care & ADLs Communication Ability to undertake tasks Learning & applying knowledge Psychosocial adjustment	Educational opportunities Employment opportunities Community integration Socialization Family functioning Recreation Quality of life
Body Composition	Body fat & obesity Lean tissue
Bone and Joint	Joint Contractures Spine Deformity Osteoporosis Fractures Pain
Lungs	Restrictive Lung Disease Pulmonary function Cough/pulmonary toilet
Heart	Cardiomyopathy Conduction defects Cardiopulmonary capacity
Gastro Intestinal and Nutrition	Dysphagia Constipation Cachexia (late onset)
CNS	Mental functions Intellectual capacity

Although the degree and severity or even occurrence varies, the characteristics of most of these disorders include the primary condition (impairment) of progressive muscle weakness and atrophy and the secondary conditions of obesity, limb contracture, spine deformity, pain, decreased pulmonary function (restrictive lung disease), cardiac disorders and intellectual impairments.

Medical Management of Neuromuscular Diseases

With rare exception there are no specific treatments for the many neuromuscular diseases (such as insulin for diabetes). Treatment is usually restricted to the secondary impairments. These conditions, unless corrected or prevented, usually lead to activity limitation. This loss of function, if not correctly managed, frequently results in participation restriction and reduced quality of life.

References

A Teacher's Guide to Neurmuscular Diseases, Muscular Dystrophy Association , 2005

Carter GT, Ed., Physical Medicine and Rehabilitation Clinics of North America . 1998 Feb;9(1) Full text on nmdinfo.net by permission.

Jones HR Jr, De Vivo DC , Darras BT. Neuromuscular Disorders of Infancy, Childhood, and Adolescence: a Clinician's Approach 2003, Butterworth/Heinemann, San Francisco .

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