Progressive acquired or hereditary neuromuscular diseases are disorders caused by an abnormality of any component of the lower motor neuron—anterior horn cell, peripheral nerve, neuromuscular junction (pre- synaptic or postsynaptic region), or muscle.
While some neuromuscular diseases have pathologic abnormalities isolated to one anatomic region of the lower motor neuron, with primary or secondary changes in muscle, other neuromuscular diseases have been recognized as multisystem disorders.
For example, myotonic muscular dystrophy may affect skeletal muscle, smooth muscle, myocardium, brain, and ocular structures; Duchenne muscular dystrophy gives rise to abnormalities of skeletal and cardiac muscle, the cardiac conduction system, and brain; Fukuyama congenital muscular dystrophy affects skeletal muscle and brain; mitochondrial encephalomyopathies may affect the mitochondria of multiple tissues.Neuromuscular diseases may be acquired (eg, poliomyelitis, Guillain-Barre syndrome, myasthenia gravis, or polymyositis), but the most common etiology is genetic (eg, spinal muscular atrophy [SMA], Charcot-Marie-Tooth [CMT], congenital myasthenic syndrome, or Duchenne muscular dystrophy).
Tremendous advances have occurred in the past two decades in our understanding of the molecular genetic basis and pathophysiology of neuromuscular diseases affecting children and adults. Traditional approaches to the classification of neuromuscular disorders utilized clinical history, family history, clinical examination findings, electrodiagnostic findings, and histopathologic analysis of muscle and/or nerve biopsy specimens to provide clinical diagnosis. Molecular genetic advances have led to the discovery of specific genes for hundreds of neuromuscular disorders and have provided pathophysiologic explanations for phe- notypically divergent disorders.
Appropriate rehabilitation management of neuromuscular diseases requires an accurate diagnosis. The clinician must be able to obtain a relevant patient and family history and perform focused general, musculoskeletal, neurologic, and functional physical examinations to direct further diagnostic evaluations.
Laboratory studies include relevant molecular genetic studies in certain instances; however, specific genetic entities need to be strong diagnostic considerations, because these studies may be expensive and have limited sensitivity and specificity. Electrodiagnostic studies may help guide the acquisition of further diagnostic studies such as genetic studies and muscle and nerve biopsies. There has definitely been a trend away from the utilization of electrodiagnostic studies in the diagnostic evaluation of pediatric neuromuscular diseases. All diagnostic information needs to be interpreted, not in isolation, but within the context of relevant historical information, family history, physical examination findings, laboratory data, molecular diagnostic studies, electrophysiologic findings, and pathologic information, if obtained.A skilled synthesis of all available information may provide the patient and family with a precise diagnosis or as accurate a diagnosis as is medically possible, prognostic information (if available for a specific entity), and anticipatory guidance for the near future. Knowledge of the natural history of specific neuromuscular disease conditions helps in the ongoing rehabilitative management of progressive impairments, disabilities, and handicap.
This chapter summarizes the diagnostic evaluation, natural history, and impairment profiles and rehabilitation management of childhood neuromuscular diseases.