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  • Bulbospinal muscular atrophy
  • Hereditary neuronopathy
  • Progressive muscular atrophy1
  • Werdnig-Hoffman disease

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  • 335.0 Werdnig-Hoffman disease
  • 335.1 Spinal muscular atrophy
  • 335.10 Spinal muscular atrophy unspecified
  • 335.19 Other spinal muscular atrophy

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  • G12.0 Infantile spinal muscular atrophy, type I [Werdnig-Hoffman]
  • G12.8 Other spinal muscular atrophy and related syndromes
  • G12.9 Spinal muscular atrophy, unspecified

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Description

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  • Group of 4 subtypes of degeneration of anterior horn cells that results in progressive muscle atrophy
    • Spinal muscular atrophy (SMA I), Werdnig-Hoffman (acute)
    • Spinal muscular atrophy (SMA II), Werdnig-Hoffman (chronic)
    • Spinal muscular atrophy (SMA III), Kugelberg-Welander
    • Spinal muscular atrophy (SMA IV)

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Essentials of Diagnosis

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  • Autosomal recessive genetic disorder that results in a lack of survival motor neuron gene1 on chromosome 5q11.2-133

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General Considerations

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  • SMA type I: weakness between birth and 3 months of age
  • SMA type II: signs and symptoms by 3 years of age
  • SMA type III: signs and symptoms between 2 to 9 years of age
  • SMA type IV: adult onset

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Demographics3

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  • Type I: 27% of all SMA cases
  • Types II and III: 46% of all SMA cases
  • Type IV: 8% of all SMA cases
  • Werdnig-Hoffman 1:10,000 births
  • Kugelberg-Welander 6:100,000 births

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Signs and Symptoms

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  • Fasciculations (especially of tongue)
  • Muscle weakness
  • Hypotonia
  • Muscle atrophy
  • Decreased or absent deep tendon reflexes
  • Difficulty feeding (infant)
  • Lack of extension during Landau reflex
  • Contractures (type 1)
  • Scoliosis
  • Trendelenburg sign during gait

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Functional Implications

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  • Inability to sit independently
  • Inability to ambulate
  • Require assistance with all activities of daily living

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Possible Contributing Causes

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  • Autosomal recessive genetic disorder on chromosome 5q11.2-133

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Differential Diagnosis

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Laboratory Tests

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  • Genetic testing

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Imaging

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  • Plain radiograph for scoliosis

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Diagnostic Procedures

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  • Electromyography (EMG)
  • Muscle biopsy

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Medication

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  • Hydroxyurea
  • Valproic acid

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  • Geneticist
  • Occupational therapist

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  • Head lag when infant pulled into a sitting position from supine
  • Poor head control
  • Inability to sit
  • Inability to pull to stand
  • Inability to walk
  • Contractures of biceps and wrist flexors

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  • Hammersmith functional motor scale for children3
  • Dynamometer
  • 2-minute walk test
  • Manual muscle test
  • Forced vital capacity

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  • It is important to avoid fatigue during intervention with patients who have SMA.
  • Strengthening
  • Stretching to prevent contractures especially of wrist flexors
  • Developmental activities
    • Prone on elbows with assistance
    • Supported sitting
    • Supported standing
    • Facilitating pulling up from sitting into standing at furniture
  • Pre-gait activities
  • ...

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