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

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

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


  • Group of four 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)

Essentials of Diagnosis

  • Autosomal recessive genetic disorder that results in a lack of survival motor neuron gene1 on chromosome 5q11.2-132

General Considerations

  • 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


  • 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

Signs and Symptoms

  • 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

Functional Implications

  • Inability to sit independently
  • Inability to ambulate
  • Require assistance with ADLs

Possible Contributing Causes

  • Autosomal recessive genetic disorder on chromosome 5q11.2-132

Differential Diagnosis

Laboratory Tests

  • Genetic testing


  • Plain radiograph for scoliosis

Diagnostic Procedures


  • Geneticist
  • Occupational therapist

  • 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

  • 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 ...

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